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qtVlm Cheat Sheet
David Burch

The free, donation-supported navigation and weather routing program from France called qtVlm has a tremendous number of features, but the Starpath Online Navigation and Weather Courses do not use all of them. These notes refer to the main features we use in those courses. These are just quick reminders of the controls. Refer to the thorough qtVlm User’s Manual for illustrated details. See also our growing playlist of video tutorials. Send comments or suggestions to [email protected]. We use object and attribute abbreviations in some cases. See our textbooks or Caris online catalog for definitions.


1.1 Terminology 
      Read me first
1.10 Keyboard
2.1 Boat settings 3.1 Pathways 4.1 Grib files, loading 5.1 Technical
1.2 Setup tips and
1.11 POI, marks,
2.2 Instruments 3.2 Polars and VMC 4.2 Grib files, viewing 5.2 Backups
1.3 Chart work 1.12 Google Earth
2.3 Tracks 3.3 Grib reckoning
      DR under sail
4.3 Meteograms 5.3 Mobile versions
1.4 Selecting and
1.13 Search vector
2.4 Alarms 3.4 Routes 4.4 Buoy, station, and
      ship reports
5.4 Shapefiles
1.5 View ENC chart
1.14 Depth contours
        and soundings
2.5 Danger cone
      COG predictor
3.5 Routing
      using isochrones
4.5 Graphic WX maps
      and images
5.5 More support
1.6 Ruler tool 1.15 Changing region
        in view
2.6 Simulation 3.6 Barriers 4.6 Merging grib files 5.6 Predictor alarm
1.7 Piloting
      and chart plotting
1.16 S63 charts 2.7 Connect GPS
      and NMEA
3.7 AIS 4.7 Compare models 5.7 Restore complete
1.8 Tides and currents 1.17 NOAA catalog
        and chart updates
2.8 North-up or Course-up display 3.8 Replay NMEA 
4.8 Forecast zones  
1.9 Text and labels 1.18 Chart Notes     4.9 Waves  


1.1 Terminology 

Readme First










PC vs Mac






grib vs grid

qtVlm is a versatile program with many features and options, often with several different ways to access them, and sometimes several separate settings can influence how a feature appears or functions. Hence the value of a "cheat sheet" that is mission oriented toward specific tasks. There are, as with all nav apps, unique names for certain features and parameters. The app is originally in French, oriented in large part to a European audience, but the English version is readily usable once we learn a few conventions in play, which are required for any sophisticated navigation and weather program.

This is also a program oriented toward sailors, where wind and sailing performance data (polar diagrams) are always taken into account in routing, planning, simulation, or replay of stored data. For pure powerboat work on under power in a sailboat, we have to specifically tell the program to use the engine and not the sails.... but we must still have wind loaded for any work with routes or simulation.

The program can be operated with any pointing device desired, but a comfortable, effective mouse with a roller wheel became our favorite fairly quickly. The Mac Magic Mouse does not work well in our experience (and abilities!)

The Windows PC version and the Mac version are essentially identical in terms of function and interface. To simplify the presentation here we use only the Mac keystroke commands and terminology, with the understanding that the keys translate this way:

Mac PC
cmd ctrl
opt alt
menu qtVlm/Configuration/ menu qtVlm/Configuration/
The keystrokes for these two controls do not follow standard correlations:
opt +x alt+ x
An alternative way to get to the Configuration screen is to use the keys below that take you to the vector chart setup page, and then change to the tab you want.
cmd+opt+v ctrl+alt+v

Grib is a WMO data format designed to transmit digital weather data. Such data files have extension .grb, .grib, .grb2, etc. Each grib file presents data on a regular lat-lon grid, the spacing of which determines the resolution of the data. Spacing of 15 nmi (i.e., GFS) is low resolution; spacing of 1.35 nmi (i.e., NBM CONUS) is high resolution.

Microboard The boat symbol, top right of the screen. Click it to toggle on/off the Dashboard. Click COG/SOG on microboard to center on boat; click the Start NMEA to turn on your live GPS and other instruments, or turn on a file of previously collected NMEA data, or an external simulator. Underway sailing a polar (in real wind or simulated wind), the true wind direction is shown here as well as the optimum course to the destination (VMC).  Microboard on/off under menu Boat, top line.
Dashboard Large set of important controls/displays on left side of the screen, turned on/off with a click of the Microboard or menu View/Show Dashboard. You can also hide the Dashboard by clicking the boat in the Dashboard's Position tab.


These are optional terms used in qtVlm for what other programs might call simply waypoints or marks. The first three are the categories of the of the points we can choose when defining them, but the default POI (point of interest)  in likely adequate for most applications. See distinctions and interactions in the Marks section.  The term waypoint (WP) appears at various places in the program, usually referring to the next mark or the active mark in a route. It is not an assignable category; just a generic way to refer to one.
GC / RL GC is Great Circle; RL is rhumb line. See notes on RL vs. GC in qtVlm.
SHOM Service hydrographique et océanographique de la Marine, which is the French Naval Hydrographic and Oceanographic Service.


qtVlm has several products that might be thought of as "routes" from the perspective of other popular navigation programs.

Pathways are the closest one to the conventional "route" concept. It is just a connected sequence of waypoints. It does not require a grib nor a polar, because the pathway has no means of propulsion assigned to it. The tooltip shows just range and bearing between points. The engine speed of the vessel also does not affect it. We use the pathway for plotting piloting fixes on the chart, or for laying out a specific line at a given bearing—of for creating what other programs might call a "route."

Routes are a unique product of qtVlm. They look like, and are set up like, a pathway, but their properties are tied to the sailing or motoring performance of your vessel. In short, it is a pathway with an assigned means of propulsion. Under sail they show the way from one waypoint to the next that is allowed by your polar diagram and the wind forecasts stored (grib). Under power they are basically the same as a route from any program, with the bonus of making current corrections, but under sail, they are a concept new to many sailors.

Routing is the name qtVlm uses for the result of an optimum route computation using isochrones to find the fastest time between two points using the boat's polar diagram and the forecasted wind, current, and sea state. A routing is an intermediate result that must be converted to a route for navigation. A basic routing computation is easy to execute, but there are several settings and other nuances to consider before counting on it to be the true optimum route to sail.




Barriers are user-defined graphic limits to computed routings, and to signal alerts if crossed during real or simulated navigation. See Barriers.

Cranks are a qtVlm in-house term for the step size used in routing and reckoning computations. The default value is 5 min. This can be changed in menu Configuration/Boat/Crank duration.

Course through the water (CTW) and heading (HDG) are for the most part interchangeable. When referring to DR or grib reckoning we would use heading (HDG) as it is an idealized concept. The actual direction the boat is pointed at any moment is its heading, but when we display the heading we are steering and then reading with a heading sensor it would be called and displayed on meters as course through the water (CTW). In actual sailing with live NMEA input, we can average the instantaneous headings to get a moire accurate CTW. See data smoothing.

1.2 General tips and setup 
Ways to access qtVlm controls (1) Right click the screen, (2) Toolbar icons, and (3) Menu bar menus. Toolbar icons itemized.
Configuration Configuration The main setup page on a Mac is at menu qtVlm/Configuration (keystroke cmd+,) and on a PC it is at menu qtVlm/Configuration (keystroke alt+x). See general info in the Readme section
Settings changes

When making changes to the settings, be sure to finalize your settings with the OK button or by pressing the Return or Enter key on your keyboard. The various settings windows can sometimes be re-sized in such a way, or appear in such a way when first opened, that the OK and Cancel buttons do not show, so you must scroll the screen to access them. There will always be some way to finalize a setting. Use of the Enter key (PC) or Return key (Mac) should close the window, which signals that the settings were received. If you tab to other settings windows before closing, the final closing should set all of them.

Size of things
the screen

You can change the appearance of most functions with the menu Configuration/General/Colors/ dropdown.  To set sizes (most restart to see some of these take effect): *** need to add each of these links

Boat icon
Status bar text
Grib time text
Chart scale display
Sun terminator

Working files

root folder

All qtVlm working files used by the program are stored in the "qtVlm root folder." You can assign this location anywhere you choose during the install, but the recommended locations would be ~/Applications/qtVlm for the Mac or C:/Program Files/qtVlm for a PC. Both Mac and PC offer programmers multiple options for storing such auxiliary files, but qtVlm is admirably clean in this regard, using just one location for all data. In either computer, if you delete that folder you will have removed all traces of the program from your system. Likewise, we can compress and back up this one folder, move it to a safe place, ready for a backup or transfer to another computer as called for.
Units See menu Configuration/General/Units and Language. Set language, position format, speed units, ft or meters, temp F or C, time format UTC or local, and day-month format, plus CSV output options. True or magnetic directions is set under menu Boat/Boat Settings/Variation

Position boat

Center on boat

Auto follow

— You can right click the chart at any location and move the own-ship vessel icon to that location (Move boat here). It can be convenient to place the boat where you will be working on chart problems or weather analysis, because there is an option to have the program always open centered on the boat. Chose that at Configuration/Boat... then Center on boat at startup.

— To digitally place the location of the boat, right click the boat and choose Set-up position. Or, turn on Dashboard, click Position tab, then press Position button and enter location. This digital positioning cab only be done when no NMEA connected and no simulation on going or NMEA file running.

— Clicking the COG/SOG data tab at the top of the microboard centers the view on your boat.

— Or with keyboard: opt+B toggles this on and off

— For default operation, you can set this to be always on at Configuration/Boat... then Auto center, but this is likely best reserved for actual underway navigation.

— Important functionality: Whether this centering is set to automatic, or if you turn it on manually with one of the options above, whenever you manually move the chart or the boat, it shuts off the auto follow feature and you then need to turn it back on if you want it to continue.

Center on Mark cmd+M opens Marks Manager, select a mark then press Center to go to it. If you have several places you want to go back and forth from, drop a mark near each of them (right click/New mark) and then you can go directly back and forth, from day to day.

Sun Terminator


Day/Dusk/Night mode

The default display has day and night marked with a shadow. This offers a very nice quick view of when it will get dark, or who is dark and who is light, etc, but if this extra shading interferes with what you are doing with the program you can shut this off with menu View/Show hide/ Night zones.

The sun terminator location defaults on start up to the present time, but it will then respond to the Grib time shown in the the top left of the screen. Thus if you load a 16 day grib file for any location on earth you can set the time step in the tool bar and then step the sunset time across the globe to learn if it will be dark or light when you arrive at a specific place. Turn on the Dashboard to see the phase of the moon change as well so you will know about moonlight.

There is also a general display option at View/Light Mode, common to most nav programs. Choose Day, Dusk, or Night. For our course work this would stay on Day.

Full-screen mode A check mark in the menu View/Full Screen mode will switch the present display to full screen, and then it will open again in full screen mode after quitting, even if you had manually taken it out of full screen mode before quitting. With that unchecked, the program opens in the window mode it had when you quit or closed the program. For PCs the menu bar stays in view on Full screen but not on a Mac. On a Mac to get to the menu slide the cursor up against the top of the screen and that will reveal the menu bar.
Copy a location If you want a text copy of the coordinates of any location, put a mark there, then use the Copy button provided in the Mark set up window, then just press Cancel. That will put the coordinates onto your clipboard to be pasted elsewhere. The result will be in ddd.dddd format, regardless of the setting selected in Configuration.
1.3 Chart Work 
Types of charts

Several kinds of charts can be used; we start out with the two basic nautical types, RNC and ENC, along with the OpenStreetMap option for practice on land—or for navigation in view of streets and buildings that are not on the nautical charts.

Step one is obtain the charts you want and copy them to your computer. They will generally come in compressed zip files, that will then have to be unzipped. See video playlist. For US charts, see

We do not cover CM93 charts in this course. qtVlm will also load georeferenced satellite images, weather maps, Google Earth screen caps, and other geographic images that we can navigate upon, covered below.

Show or load
a single chart


View chart thumbnails

With no charts loaded, or many charts loaded, in view or not in view, you can load just one chart, vector or raster. Use menu View/Single chart/Open a chart or use the keystrokes cmd+K. Once selected (see selection notes below), this will give a thumbnail preview, plus other chart info.

Press Show at nominal resolution and it will center the chart and set the display scale to match the compilation scale of the chart. The Fix Header button is only used for (unofficial or official) KAP files (RNC) that will not load. This is rare for official KAP, but sometimes a line is missing from an index table that describes the image, or one of the georeference points is mis-typed. The Delete button actually does delete that one KAP file from your computer. If there are other related files in its folder this does not affect them. For a single ENC, the delete just removes it from the screen and leaves it on your computer. The KAP behavior may be a bug?

When done with this chart, you can close it from the same menu (Delete button), or alt+K, or click R or V chart icons in the toolbar to return to the main chart set. Even if no charts are loaded, this step will close the single chart.

Important: When selecting a single chart from your computer, this would likely be either RNC or ENC. When you get to your RNC folder you find that chart is made of two files, a BSB file and a KAP file. You must select the KAP file. Likewise for a specific ENC folder you will find multiple files, with several having digital extensions, .000, .001, .002,.... At this stage you must choose the one ending in .000. That is the main ENC file; the others are updates.  qtVlm will read and apply the updates, but we must choose .000 at this step.

When viewing a chart from a set of installed charts, you can right click, and choose Show only this chart. Close as above.

Chart borders on RNC show when viewing a single chart. US charts have useful info in the RNC borders; Canadian RNC include Sailing Directions info in the borders as well. ENC do not have border areas.

The cmd+K load single chart dialog is an effective way to get a thumbnail view of your charts, even when the goal is not to load a single one. We can picture these outlines to some extent with the Show chart outlines option, but not as clearly as we do this way looking at each thumbnail individually. Just browse your list and you see them individually. Very nice.

Load multiple charts






Chart Folders window










charts don't show up

Step 1. Loading or installing charts simply means telling qtVlm where you have the charts stored on your computer. RNC and ENC are computer files typically located somewhere on your hard drive, but they could be on a movable drive such as a thumb drive or SD card, or they could be on a network drive (qtVlm allows network access, other programs do not). US charts are free and found at They are updated weekly at NOAA, but we must fetch them ourselves to update. There is also a list of latest editions at the /getcharts link.  There are several steps below here, but this will become all automatic very quickly.

Step 2. Assign the chart folders at Configuration/Charts/ Rasters and Vectors/Folders (or keys: opt+cmd+v) then Folders. Once you have the Rasters and Vectors folders window open, press Add, and then navigate to the folder where the charts are located. Then click Open. That will put a check mark in that location and you are done—or you can add more folders as needed. Note that you are assigning a folder, not  chart, and that it will automatically include all charts in any sub folder below the selected one.

Step 3. When you have completed your assignments of the folders, press OK or Enter key to close the Folders select window, then at the bottom left of the chart set up window press Delete names database S-57. This is the Search index that will then be rebuilt to include your newly assigned charts when you first do a search.

Step 4. Then close out of the chart set up window and your charts should show... assuming the chart toolbar icon R or V or both are on, and assuming you are viewing where the charts are actually located. It is not uncommon to install charts for one part of the world while you are viewing another place at the moment.  Use the 1:1 toolbar button to see the whole earth, then do a region select drag with the cmd or ctrl key down to zoom into that region. If you do not see the chart outlines, be sure they are turned on.

Step 5. When you are done using charts for some period of time, you can go back and uncheck them in the Folders window. You do not need delete the entry, especially if you are coming back to them at some point, just uncheck it.  Also you can leave it checked if you do not have many charts, but if you do load a lot, say two full states worth, then you might just check these on and off as you need to look at them. At some point, too many active charts can affect performance.

When you Remove a folder that you had assigned earlier, it just removes it from this list. It does not affect the chart files on your computer in any manner. If you are updating charts and want to replace them or get rid of old ones, then you do this with normal file management controls on your computer. If you accidentally delete charts on your computer that you were counting on in the program, they will just not show. No other impact. Just download the charts again and put them where you want them, or reassign to a new folder. When removing a link to a chart folder you do not need to delete the names database; that is only required when adding a folder.

After adding new chart folders, it is valuable to press the Force rebuild button (next to the Folders button). This will often take place automatically, but not always. Also, at the bottom of the charts set up page there is a Delete names database with the S57 button checked. This is the database used for search chart function, so we want to delete that and start over. When you do your first search after deleting the database, you will get the request to rebuild the database and it will then add all the names from the new charts.

qtVlm has two default folders (/kap and /vectors) in the qtVlm root folder that are there as potential places to store your charts, but we recommend keeping charts separate from the main program folder. Then we will back up the program and the charts separately. See backup

Online charts such as OpenStreetMap must be loaded when you have an internet connection, but once a region is viewed, qtVlm will save a copy (with some limitations) for later use off line. See details at OpenStreetMap.

Charts don't show: qtVlm can read charts you have stored on any directory or hardrive and even across a network. If you are using a cloud drive that mirrors files on a local drive, sometimes the mirrored copy is not really there, just the file name is listed. Thus you can get tricked by assigning that dummy file name to a chart folder. Everything will look right, checked and double checked, but it won't show the chart. You have to then right click that file name and make it "available offline," then it should work.

Charts don't show: We have many ways to load and select charts to view, chart groups, NOAA catalog, etc, and we can manually assign or delete folders, so we should not be surprised when we exercise a lot of these options that we might not see the charts loaded that we expected. In this case return to the Rasters and Vectors setup page, and next to the Folders button press Force Rebuild and that will solve the problem if nothing else is wrong.

* * *
Charts at this position
* * *
This is a powerful function when you have many charts loaded at different scales, in which case there are usually several charts covering a specific position on the chart. To use this function, right click the chart and choose Charts at this position, and you get a very nice display of all charts covering that position, with a thumbnail and description, and the option to zoom to that chart (leaving others still loaded) or open that chart only.

Chart Groups



don't show up

In the chart set up window, there is an option to define chart groups, then choose chart links above to assign to those groups. A group could have just one link in it or more. Then, with each of the chart locations turned on at the top, you can control which chart groups are active using the menu Charts/Chart groups/Vector and raster groups/...list of groups from which you can choose the group you want active and others will be off. It is up to the user to figure ways to use this. See this video explanation of this special function.

If you are using training charts, for example, in a course, you do not want to update these, so if you have a set of state charts you are updating for actual navigation you do not want to mix them. Thus they can go into two folders and assign each to a group and then you can turn on the ones you want with the group option faster than from the folders option... but it could be done either way.

If two charts of the same area are loaded, the newer one will dominate, so that could confuse the use of a training chart... and ENC training charts are not marked as such, we can only know by doing Chart Info and read the date.

After defining a group and then assigning a folder to it, you have to say OK twice. Once to store the groups set up and once to store the chart folder set up.

If no charts show when you know you have them loaded and turned on, then check the chart groups menu. Maybe the chart you want is in a group that is not turned on. Then you need to change that to All charts, or select the group with the charts you want.

Selecting chart types


Toolbar chart icons

Chart types are selected and activated with the chart icons in the left of the toolbar, R for RNC raster, V for ENC vector, and O for Online charts, of which we will use the OpenStreetMap. We hide for the time being the C icon for the global set of vector training charts called CM93, not used in this course.

The chart icons go gray for a moment after clicking, then they turn "chart colors" once enacted. You can activate one or more types at the same time. Both can be seen when they are adjacent. To force only one type of chart, shut other options off.

If you have both R and V active, the quilting algorithm will choose the chart that most closely matches the display scale you are presently viewing, with a preference for the ENC if there is one of each at the same scale. If this convention is distracting, just shut off the type you do not want to see. See details below on Chart displayed with scale change.

General chart information A right click on any chart and then clicking Chart information or the keystroke ctrl+alt+I (Mac opt+cmd+I) brings up a screen that tells all about the chart in view: name, scale, edition, version, date, depth units, soundings and height datums, links to chart notes, as well as a unique and valuable qtVlm feature of listing all the depth contours in that chart.
Chart outlines Turn on at Configuration/Charts/Rasters and vectors... then Show chart outlines. There are blue and red outlines. Blue outlines charts that are being seen, if even just a small corner. Red are charts that are fully behind one or more of the blue outlined charts. There is no color distinction between vector or raster charts when both are loaded.
Show a Lat-Lon grid Use menu View/Show-Hide/ShowLon-Lat grid


No charts show

(1) Be sure the assigned folders are still correct. Check first with loading a single chart (above).

(2) Check that the folders are not duplicated i.e., MyCharts/ENC/NY/NY/then the charts. Windows unzipping sometimes duplicates the folders. This can prevent loading a folder of charts.

(3) Error msg on startup: "No folder defined for this type of chart." Likely means that in Configuration/Charts at the top you have coastlines assigned to S57/S63 or to CM93, but do not have any of those chart locations defined. Turn off that switch to remove the error msg. Or... you have that switch turned on, but no check in either of the boxes.

Chart quilting Chart quilting means that when a series of adjacent charts are shown at the same time, the program trims off the borders and matches them up properly along the edges. This offers a convenient, continuous overview of the charts available, but at the expense of a periodic mismatch in compilation scale, and sometimes even of depth contours. See discussion in the textbook. Some navigation programs have a specific control for "quilting," but qtVlm does not. This is not really needed. You have the option to load just one chart (see above) or load all charts in a specific assigned folder, and in the latter case, the charts are automatically shown quilted. To view any one of them alone, right click it and choose Show only this chart.
Distance scale and zoom level

The distance scale display is turned on from menu View/Show-Hide/Show scale. Once this is turned on, it appears on the chart where it was last positioned. You can then right click the chart at any location and move the scale there. The default display shows a linear scale, along with the display scale of the chart, which can be compared to the chart's compilation scale found from right click/Chart information. That display offers the option to set the display scale to the compilation scale.

Also shown is a scale factor called zoom scale; it is a parameter used by several networks of alternative chart options. It is not an official ENC or RNC parameter. When not using these custom charts, the zoom level has no direct application, so it can be shut off at Configuration/Charts on the top right. But there is an indirect application: when turning on tides and currents icons to show the stations, they appear as little gauges (tides) or arrows (currents), but only if you are zoomed in to a zoom level equal to or larger than the value set at Configuration/Gribs and Harmonics/Harmonics and weather stations. The default 12 is fine, or maybe 11, but smaller and the display can be overwhelmed with these symbols.

Font size of the scale display is set at menu Configuration/General/Appearance/Labels font size. Default is mid scale; if too small, try three-quarters scale. Other labels change as well with this.

Selecting and zooming See also Selecting and zooming  for more details.
Chart scales and overzooming, 

Each chart has a compilation scale such as 1:40,000, which means when viewing the chart at this scale, 1 inch on the screen would be about 40,000 inches on land (roughly 0.5 nmi). You can display the scale being viewed by turning on the scale at menu View/Show-hide/Show scale. Then once it appears on the screen you can move it to where you choose with a right click /Move scale here. The scale shows a distance scale along with the chart's display scale in view. On a 1:40,000 chart, viewed at that scale, the 1 nmi long line marker will be about 2 inches long. The + and – buttons change the scale by a factor of 1.3.

Recall that that chart scales are named as fractions, so a 1/80,000 chart is "smaller" than a 1/40,000. Once you zoom an ENC in to a display scale that is more than twice its compilation scale (i.e., viewing a 1:40,000 chart at 1:20,000 or larger), the warning "Overzoom" will appear on the top of the screen. The more overzoomed the display becomes, the larger the sign. Put the cursor on this sign to see what chart number is being overzoomed and how much overzoomed it is. If there is more than one chart in view at the moment, this will also report what faction of the screen this specific chart takes up—this can alert us that maybe only a small part of the display is actually overzoomed.

This unique overzoom warning applies only to ENC. When using RNC, we can generally tell by looking at the chart if we are in danger by an overzoomed display. With RNC, there is a natural limit as the image becomes pixelated and hard to read, but with ENC the objects remain integral, so sometimes it is valuable to overzoom to see our location in a marina for example, but we must keep in mind that we are likely working beyond the promised accuracy of at least some data on the chart.

How charts in view change

When we have a large range of charts installed for a given region from smallest scale to largest scale, qtVlm has to decide which one it shows us as we change the scale in view, which is does this way. It will look at the scale you are viewing (which you can also display on the screen as noted above) and show the chart that has a native scale closest to the one you have, whether it is ENC or RNC. If you have both at the same scale, then it will favor the ENC. As noted, you can force only one type or the other with the chart icons in the toolbar. 

Then as you zoom the scale in or out, the chart showing will only change when you cross over the midpoint between the two scales, i.e., with 1:20,000 chart, 1:40,000, and 1:80,000 loaded, you will see the 1:40,000 for all display scales between 1:30,000 and 1:60,000, which mark the transitions between sequential charts. When you first see a new RNC chart, the writing may not be legible at the zoom level, but if you do want to read it, do right click/Show this chart only, then you can zoom to see details. To return to all, click the R chart icon.

Draw random lines or figures on the chart with Barriers

There is a tool called Barrier that has serious applications when routing in that it can block the boat from crossing it. See use of barriers in routing. But if we are not routing, and just want to annotate the chart with a line, path, or figure, we can use this tool. For example, suppose you want to compare the lay of a depth contour on an ENC to an RNC, or mark the boundary between a red and white sector of warning light. 

Procedure: If you intend to use this, then go to Configuration/General/Toolbar and turn on the icon for it. Looks like a street sign.  Then to start, use menu Barrier/Add barrier set, and call it, say, "Random lines." Then click Add barrier or click the toolbar icon and draw your line or figure... or simply right click and choose Add a barrier, but that choice will start where you clicked.  Right click to remove individual segments, or delete barrier set to remove all. You can also edit the line. You can assign each set a separate color.  This is a novelty in these drawings, but a serious tool when routing... i.e. this is how we tell a route computation to not go through this Pass.

Land colors

Through rarely called for, you can change land color under Configuration/General. In Europe there could be a preference for the official French (SHOM) chart colors, but elsewhere less so, and indeed for US charts we are best to turn off SHOM colors in menu Configuration/Charts/.. Rasters and Vectors / Vector Charts / General


ENC alarms work as long as the corresponding ENC has been loaded (i.e. assigned a folder where it actually is), even if not showing. This allows us to take advantage of alarms even when using RNC or image charts. See alarms.

Coastlines For computed routing solutions that must avoid hitting land and for activating alarms that can detect land ahead, we need to specify what map system defines the coastlines. This is done in Configuration/Charts top line. If we have the appropriate ENC loaded we would use S57/S63, else the default with the switch off will be the base maps, GSHHS. It is important that this be set right when running simulations. We do not use CM93 charts in our courses.
Moving around the world of charts

When moving to a new location on the chart that is a long distance off, such as another corner of country or to another country, you can use the 1:1 magnifier icon in the toolbar to revert to global view, which is faster than manually zooming out. Then you can cmd-drag to set a window on where you want to view.

Alternatively, the search function is often the fastest way to move from one place to another if you know the name of any object bear the location you want to go to.

Shift+drag Note the shift+drag, select, and delete option for marks etc... very nice. Will not delete locked mark.
(cursor over)
qtVlm has many examples of actions based on cursor location without clicking (cursor over) in the form of data popup. This is often called a tooltip. Sometimes this is a bit slow to respond, so pause on the target as needed. With multiple windows open, be sure qtVlm has the focus... i.e., click the chart then put the cursor over the item, such as a selected area, route, pathway, or track. Note that track tooltips are the only ones that must be turned on (menu Boat/Tracks/Activate track tooltips). All other tooltips are always on.
Course up display See under simulator.
1.4 Selecting and zooming 
Region select

Turn on selection mode with the blue square toolbar icon, next to the 1:1 button.  It will switch to orange when engaged. You can then left-click and drag to select an area on the screen. Alternatively, activate it with menu View/ Selection mode. Once you have selected the area of interest you can:

— zoom to that area (right click)
— delete all or part of the objects included (delete key or right click)
— load a grib file into this region (right click)
— search the chart for objects by name within the region (cmd+F)
— use region zoom selection as an alternative to the Ruler tool (see below)

If you change your mind, shut off selection mode with a click of the orange toolbar icon or press the ESC key.

region select
To select a region directly use shift + left-click drag. This will define the region, then right click to choose options. This is the same as clicking the blue selection tool in the tool bar, but may be more convenient for some users. The shift just disengages the normal chart drag and draws the box.

region zoom

To directly zoom to a region, do cmd + left-click drag and release. If you accidentally zoom to a small region you do not want to be in, then use the magnifier 1:1 button in the toolbar to get back to global view and then start again.

Region select as a ruler tool The region select option will draw a line from top left to bottom right corners marking staring  and finishing positions of a line segment. While drawing this box and line, the GC  initial heading and distance along with the RL heading and distance show in the status bar for a few seconds, after which you can read these values from a tooltip with the cursor over the selection. Construct the selection in the direction you want to measure if using the tool for this purpose. Sometimes this is more convenient than the Ruler tool, other times not. Escape key shuts off the selection.
Troubleshooting If after using the selection mode, you cannot move the chart, but only draw more selections, then the selection mode toolbar icon is still orange, meaning active. So click it to make it blue again to get the cursor focus back to the chart... or press escape key.

Ways to zoom
zoom steps

Zoom to compilation scale Right click the chart at any point and choose Chart information, at which time you can click the chart's compilation scale button and it will shift the display to that scale and keep the chart centered at that location.
1.5 View ENC chart objects 
Background on what you see on the chart Recall that the objects and attributes content of ENC is determined by the IHO S-57 standard, but that standard says nothing about how they should be displayed to the mariner on the screen of a navigation program, generically called an electronic charting system (ECS) or more specifically, the electronic chart display and information systems (ECDIS) specified by the IMO to meet the IHO standard S-52. It does not even tell us which objects should be seen. Most ECS in use by recreational mariners and many commercial vessels are not required to meet the S-52 standards, but many make an effort to match them as well as possible. One broad aspect that is common to many ECS is the option for three general categories of display complexity (display modes): Base, being bare minimum to see we are on a chart, but not enough for safe navigation; Standard, which does include enough detail for safe routine navigation, and then Custom, which is a list of all the objects on the chart from which we can choose what we want to see. All objects will always be more congested than useful. qtVlm adds a couple variations to this as noted below. See Display mode details.
Background on how you read the chart Beside the information shown on the screen, which depends on your choice of display mode and other user settings, we typically get most information about an object in view by the process of "cursor picking" it, meaning right click the object location and then choose Vector chart elements. See details on doing a cursor pick.

Display mode Configuration




keystroke commands

The S-52 standard includes these object display categories: Base, Standard, and Other; in some cases it can be valuable to know what objects are included in each. See Background and References.

From menu Configuration/Charts/Rasters and Vectors/Vector charts/General there are several choices on display mode. See display mode details.

Base and Standard for qtVlm includes the official S-52 objects according to each category (link above). Standard includes all of the Base objects, and although intended for "standard" navigation, keep in mind there are important objects not included in Standard, such as depth contours, magnetic variation, tidal current data, spot elevations, legal zone boundaries (territorial waters, exclusive economic zones, etc), shore structures, and more. Both employ SCAMIN values for all objects.

Customized lets users select from a drop down list of objects, which is not active unless Customized is selected—uncheck Quality of data as that adds large icons across the chart that are rarely useful. This mode employs the SCAMIN values for each object. Objects that are common to both Inland ENC (IENC) and ENC will appear twice in the list of choices. The first is ENC object; the second is IENC object. Abbreviations (acronyms) for the IENC objects are lowercase, which is not reflected here, but makes a difference in the object search function.

All—in qtVlm this includes Base, Standard, and Other (in other words, All), plus it overrides SCAMIN, so all objects are shown at all display scales. This mode will usually be too congested for normal use, but we may need to use it to check for specific objects.

Detailed—in qtVlm is the same as All, but it honors your other choices made in the Vector charts preferences (cmd+opt+v), namely choices for Soundings, Lights and Buoys, National texts, Important text only (default should be off as this shuts off essentially all labels), and, importantly, Detailed honors your choice for Chart information objects, which we might want to turn off as a default since the meta objects it includes can congest the display. Detailed employs the SCAMIN properties of all objects, but it also respects your choice of SCAMIN sensitivity set on the vector chart set up page (opt+cmd+v), which includes the option to turn it off.

In summary, a good starting point for Display settings would be:

Display category = detailed ...... Boundaries = symbolized
Graphic style = paper chart ....... Colors = 4 colors (refers to water colors on the chart)
3rd line leave as default we do not use these
Blur effect if overzoomed = Off
Reduce details at small scales = On, and set to mid scale (label in italics. See SCAMIN controls)
Chart information objects = Off
CM93 ...not used
Depth Soundings = On .... at least for now. Return to shut them off if cluttered
De-clutter soundings = On .... and just leave it on, unless for some reason need more.
Lights and Buoys = On, with all three options = On
Text Font and size OK for now .... can experiment with this later
Fixed text while zooming = Off ... this lets the text get bigger for a second or two, which helps read them.
Highlighted text = On ... this is a nice touch of qtVlm.
National texts = OFF ..... this will default to the English version of a place name if a different national name is included in the chart. We still see the national name in in a pick report, even with this off. When this is turned on, the labels use the national language.
Important texts only = Off ... else we see essentially no text labels at all.
De-clutter texts = On ... this prevents two labels being displayed at the same location. This can sometimes prevent a label from showing if two objects with names are close by. If you suspect this, then zoom in.
Auto adjust area labels = On .... this is a valuable feature of qtVlm that repositions charted area labels to keep them in view as you pan or zoom in such a way that would have otherwise hidden them.
Depths are a longer story and will be adjusted often in practice. For now just leave defaults (3,5,5,10m). Refer to our textbook for the role and choice of safety contour and safety depth, as well as deep water and shallow water.

You can then later experiment with the various settings and as needed turn the soundings or lights on or off.

Keystroke commands to change Display category are: cmd+alt+x, with x= B for Base, S for Standard, C for Custom, D for Detailed, A for All. You can, for example, do cmd+alt+A at any time to see both why this is not a good mode for general use, but also to check out an area to be sure you are not missing objects you might care about.

Cursor pick
to get a
pick report.

Once you have set your vector chart display Configuration (discussed below), we effectively "read an ENC" with cursor picks on individual objects:

1. Put the cursor on the chart object of interest, and right click to access the menu.

2. Left click Vector Chart elements to bring up a list of objects and their attributes at that point. The list might be long and need scrolling. At this point you can move the target point (magnifying glass icon) to read content of other nearby objects.

3. When done, click Close at the bottom of the data window.

4. A keyboard shortcut that might be preferred is ctrl+alt+P (Mac opt+cmd+P) opens a pick report for the location of the cursor, which might be behind the report. If so drag the report away and set the magnifier glass to the object you want.

Show only Visible


Show object relations

When you cursor pick an object and the pick report appears, there is at the top of the window two options: Show only visible and Show object relations. With Only visible off, you see all objects encoded at that location, which will include things like magnetic variation, quality of the data, nature of the sea bed, and various properties of the chart. Turn this on and the list is limited to objects in view, which is a  more direct list, that usually is what we want. 

Turning on object relations groups together things that are closely associated such as a buoy, its light, and its daymark, and fog signal.  Click a few objects and practice turning these on and off to see how they work.  They retain the setting you chose when you close the pick report.

Show area object extent

with the

"Magic eye"

Chart objects can be points, lines, or areas. qtVlm has a unique function to display the extent of an area object by pressing the eye icon that shows next to the object name in the pick report. We call this the magic eye. This will identify restricted zones and depth areas, amongst other useful displays. Note that the system must be in a North-up display for this function to work. If the icons do not appear, then check the course mode toolbar icon, and change it to North up. See course up.

This function works as expected in the Android mobile app, but Apple requires all popups to be full screen so you can't see simultaneously the effect of pushing the magic eye button. Thus with iOS mobile app you have to push the button, then quickly close the object data window and you will see the area of interest marked in red, which will last for about 5 seconds.


SCAMIN is the minimum display scale an object will show. Each object has an assigned value in the ENC, but this can be affected by two qtVlm settings made on the ENC setup page (menu Configuration/Charts/Rasters and vectors  or keys cmd+opt+v), which are:

(1) Scale minimum sensitivity. This slider adjusts the sensitivity of SCAMIN. When turned on, with the slider at mid scale (label in italics), all SCAMIN values are set to their charted values. Cursor pick an object to see what that display scale is for that object type. With this control turned off, there is no SCAMIN in effect, and all objects show at all display scales. Alternatively, you can make the setting more or less sensitive by moving the slider: left of center increases SCAMIN (objects removed sooner when zooming out); right decreases it (objects persist longer). Click the slider just above the line to step it. When re-centered the label goes to italics. Note that changing the slider, changes the effective SCAMIN, but does not change the charted values that you read with a cursor pick.

This tool is used to design a chart to your own liking with respect to objects shown, but keep in mind that increasing SCAMIN to or above the compilation scale removes objects that were intended to be on the chart for normal, safe usage, so this should be done with care.

There are 20 arrow key click steps between the left and right side of the scale. To recenter at charted SCAMIN, move it to one end then come back 10 arrow key clicks to see the label then turn to italics.

(2) The choice of display modes (Base, Standard, Detailed, or Custom) does not affect your SCAMIN sensitivity setting, but the display mode All turns on all objects and shuts off SCAMIN.

Lighthouse toolbar icon Lights OFF    Lights ON     Lights seen from Vessel.  First two same as setting on Charts preferences.
This icon only shows up in the toolbar when you are in vector chart mode.
Equivalent RNC qtVlm tells us the Source indication (SORIND) attribute, which includes the paper chart number that the ENC is based upon. This is valuable for checking native depth contours (see easier way in Depth contours) and also checking land features that are usually missing from the ENC—recall we can use the OpenStreetMap option as well to check land features.

1. No response to a cursor pick: Try closing the pick report window, zoom the display scale a bit, and try again.

2. Not seeing objects you know should be there: Double check you are on a display mode that includes the objects and that the scale you are using is larger than the object's SCAMIN. Recall SCAMIN sensitivity (above) can be changed.


1.6 Ruler Tool 
From a point on the chart

This is one of the most used functions in the program. It measures the range and bearing between two points, or a sequence of points. To activate the tool, right click anywhere on the chart and select Ruler tool. This will initiate the measurement from the point you clicked, yielding an active measurement to the cursor location. The text reports both the rhumb line (RL) distance and heading (from initial point to cursor) as well as the great circle (GC) distance and initial heading of a GC route between the two points. For distances less than a few hundred miles, these values will be essentially identical, but for long ocean spans, especially from two high latitudes you will see the notable differences of the tracks and distances.

For distance between multiple points, use a double click rather than single click. This way you can measure total distance along a sequence of points as well as point to point along the way.

Troubleshoot The info box of data shows up at the end of the measurement, at the second point and beyond. If this data box is then partially off screen so you cannot read what you want, then do the measurement in the other direction.

From a POI or from the boat

To measure range and bearing from the boat, right click the boat and choose Ruler tool.

To measure from a specific POI, right click the POI and then choose More options/Ruler Tool and this initiates the measurement precisely from that POI location.

Ruler tool
goes red
The ruler tool line will turn red when you cross the safety contour (when ENC coastlines are selected) or when it crosses the base map boundary, otherwise. The choice of coastlines is made in the top line of the Chart set up page (cmd+opt+v). For ENC coastlines you must have ENC installed, but once installed they do not need to be showing and the red warning will also occur viewing RNC. Likewise, the ruler line will turn red when crossing a user defined barrier line. See barriers. These

Line between POIs

Alternative ways to measure range and bearing

To find range and bearing between two POI you can also right click one of them, then choose Draw/Edit line to another POI then choose it from the dropdown and choose if you want a GC line or RL line or both drawn (for short distances it will not matter). Then when the line is done, put cursor on the line to read out both RL and GC data. For longer ocean routes this is a way to get a quick comparison of the RL heading and the initial GC heading. See notes on RL v. GC in qtVlm. This Line between POI is the most accurate way to get sailing info between two specific locations, which you can specify as precisely as you care to.

Note: the tooltip presentation of course and distance is only active while that measurement is active. If you leave the line on the screen and go to another one or another operation then the tooltip may not work when you return to it. Draw it again to get that data active.

A faster way, but not quite as precise as we cannot hit specific POI this way, is just to a region select (shift drag) from start point to finish point and then read out the data from the status bar, or put the cursor on the box to read it from a tool tip.

1.7 Piloting and Chart Plotting 
Plot a bearing line to a target

In Configuration/General near the bottom, turn on Allow POI to be moved immediately. This makes these operations a bit faster. Later you may want to come back and turn that off. If needed review Pathways.

1. In the menu bar Pathways, choose create a pathway. Name it bearing line 1; Start date and time does not matter; Pathway starting point is From 1st mark; shut off all 3 left options; turn on Reverse order; then press Append POIs.

2. Click the bearing target to drop a point there, then click in the water somewhere near where you are—does not have to be close. Then click the notice at the top center of the screen that says Stop Append POIs. If you add one by mistake, just right click it and delete it.

3. Left click and drag the last POI to set your bearing direction, with the line long enough to meet your needs.

Fix from range and bearing

1. Draw a bearing to the target (as above) with length longer than your observed range.

2. Right click the target mark and choose Edit and then add a ring to the mark with radius equal to your Configuration measured range.

3. Your fix is where the ring intersects the bearing line. Drop a mark there to read Lat-Lon.

Fix from two or more bearings

1. Draw the first bearing line as shown above. Then create a second pathway the same way with name bearing line 2 and draw that line.

2. The fix is their intersection, or somewhere within the "cocked hat" of 3 crossed lines.

Fix from two or more ranges

1. Drop a mark on target 1, then edit it and add a ring with radius equal to your measured range to that target.

2. Repeat with targets 2, 3 etc. Your fix is at the intersection of the circles that is near your DR position. There will be other intersections well removed from logical answers. 

Running Fix

A running fix requires two bearings at two different times, and we need to know the course and distance made good between the two bearings. The bearings could be to the same object or to different objects.

1. Draw the two bearing lines as shown above—to the same object or two different objects. Use pathways bearing line 1 and bearing line 2.

2.Create a third pathway ("rfix run") and start it anywhere on the first bearing line, and put the second point at the distance and course made good between bearings. Add another point to the pathway in direction of the initial bearing line and extend it long enough to cross the second bearing line. That intersection is your running fix.

Course to steer (CTS) to correct for current and find SMG

qtVlm will tell us this automatically if we know the current, but we can still solve for it in the traditional vector method.

1. From a known position, use a pathway to draw the course line in the direction you wish to make good

2. Make a second pathway with two marks, one very near the known position and the second about a mile so into the direction the current is flowing toward and end adding marks.

3. Move that first mark to be right on top of the known position mark, and then move the other end of the line to be located at the position you would be after drifting in the current for one hour. Than add to that mark one ring with length equal to your fixed boat speed (STW).

4. Append a mark to that same pathway and extend it to where the ring crosses the heading line. That direction is the CTS.

5. Use ruler tool or another pathway to find the distance from the known position to the above intersection position. That length in knots is your speed made good (SMG) as you crab along this line.

Plotting clean up Do a shift-drag to make a region that includes all your marks and pathways, then right click and choose delete all marks. This will clean up your plotting but leave the pathways for later use. If you have distinguished between POI, marks, and beacons for any reason, at this stage you can choose to delete or leave just selected categories. After right click, choose Delete marks rather than Delete all marks. This will not delete locked marks.
1.8 Tides and Currents 
Main first issue qtVlm has an an outstanding, versatile tide and current presentation. The program does not ship with any harmonics files installed, so first step is to find a set you trust and load them. Generally it is easy to find good ones for US waters as these are public domain. Videos on installing harmonics: one for PC (4:58) and one for Mac (5:48). International harmonics from from any source have to be tested against official values, some of which can be found online, others can be found in the 2020 US tables, which, back then, included many international waters. If they check out for 2020, they are likely good now.

qtVlm can read TCD files (tide constituent database), but they must be in a folder with no other files. Here is a link to Recent US data from Xtide. On a PC you will need Winrar to uncompress this. The file you want to assign in qtVlm is harmonics-dwf-202x0110-free.tcd. This will give US tides and currents. Harmonics are assigned at Configuration/Gribs and harmonics/Harmonics. (Starpath students can use the file we provide in Lesson 3.)

More than one harmonics file can be loaded and then activated as needed. Even more than one can be turned on at the same time, but if the regions overlap you end up with multiple reports at the same station or nearby—newer NOAA data have the stations better located than they were in the past, which can be a hint to recency.

Harmonics files can be stored on your computer wherever you choose and then assign to, but you might consider loading them into a dedicated folder such as My qtVlm data/My Harmonics as discussed in the Backup Section.

Access the data Use icons in the toolbar: yellow and blue gauge with a gray arrow is the tides; broad brown arrow is the currents. These buttons turn on similar icons at each point on the chart where there is data, annotated with the present values. For currents, if there are multiple depths available, the numerical value shown will be for the shallowest data. Right click any of the icons (arrows for currents; gauge for tides) to access the Details window—clicking the tide or current labels will not work.
Station icon display options Under menu Configuration/Gribs and harmonics/Harmonics on the right there are options to show current arrows in solid colors depending on speed (as opposed to outlined arrows), show current labels, and show tide labels. All three are valuable to turn on. Icon sizes are set to mid scale, which is fine, but they can be changed. Values shown in the labels will correspond to the time indicator described below. If you do not see the little gauges (tides) or arrows (currents) then you need to zoom in. The display scale (zoom level) where this occurs can be set. See discussion under zoom level.
Time zones, past and future dates, moon phase, sun up, twilights, water depths qtVlm has the most informative tide and current presentation of any program we know of. Besides its functional graphic display under the Details option, showing the current values at all depths known, you can also view data at later and earlier dates with a simple date selection. For any date shown, you also see the time of sun up (rise to set) by the length of the yellow bar. The brown extensions of that bar represent the span of nautical twilight, which is the common definition of darkness, meaning end of twilight, all of which is value for routing planning. The phase of the moon is also shown, so it is easy to plan night arrivals with a bright moon. You can also choose the time zone to display, between UTC, computer time (presumably your local time), as well as the local time zone of the station you are looking at, which again is very helpful for voyage planning in the future at some remote location. See video demo of these features in the playlist index.
Grib needed for animation To learn the most about tides and currents we want to see how they vary with time over a region (not just at one station), which we can do by stepping through an animation with the arrow keys in the toolbar. But for this to work, we need to first load a grib file. It can be anyone at all, but a simple partial VLM will do the job. The loaded grib will activate the controls. Note that a grib for wind in Cape Cod will let us look at current variation in Puget Sound, but since the interaction of the current with an opposing or following wind is so dramatic, it makes good sense to turn on the wind and watch it as you watch the currents.

Pink line
time indicator

Tide and current animation

When the tide or currents Details window is opened the "grib time" will be marked by a pink vertical line showing the time and values at that time. That time will be the same as the active time in the loaded grib file (top left on the main screen). If no grib file is loaded, this will be the present time from your computer. With this system, you can then animate the grib file or step through the times to watch both wind and currents change with time at that location.

To show tide or currents at the present time with grib file loaded, press the Now icon in the toolbar (underlined down arrowhead). Or without doing any of that, you can read the times and values easily by moving the cursor along the plotted values in the Details view.

You can animate the currents over the time period of the loaded grib file, either manually stepping through at the time step set in the toolbar (5 min up to 12 hr) using the arrows on either side of the time step, or to automate it, use the video start icon next to that. The automation will cycle through the time range of the grib file, starting from where you ask it to. Speed of the animation is determined by the time step selected. You can also animate the tides or currents by turning on the GRIB slider bar in the GRIB Configuration window (windsock icon) and the use it to move forward and backward as fast as you like.

Date selection qtVlm offers the option to set the date for the predictions using the calendar option. This is a valuable tools for planning future voyages or for working training exercises from some date in the past. Note that it will also covert the times to apply daylight time as needed.
Depth selection qtVlm is also unique if offering the option in the currents predictions to select the depth of the prediction when the station offers data at several depths. Generally small craft operators would take the shallowest data as most likely pertinent, but in some cases there are data at say 2, 4, 9, ft and more, in which case we need to consider an average of those.
Flood and ebb currents In a current plot, the positive values in green are the flood currents; the negative, blue values are the ebb.  NOAA follows this same conventions on signs (±), but they also label with F and E.
Rising and falling tides In a tide plot, a falling tide is green and a rising tide is blue. Comparing this to the currents plot, we see that these tide colors are a subtle reminder not to confuse a falling tide with an ebb current—or vice versa, do not assume a rising tide means a flood current. In many waterways, it is a dangerous business to guess the state of the current from the state of the tide.
Spot checking the predictions It is crucial to check the stations you care about with the official NOAA sources. We have articles and videos online on this process. We also have notes on how to check international stations.
Instrument display For grib forecasts or measured current (vector difference between CTW,STW and COG,SOG), the instrument for displaying the results is called CS/CD for current set/current drift.
1.9 Text and labels 
Types of text settings There are at least three categories of text controls: (1) program text font and size we see in the Configuration windows and in the status bar, (2) fonts and sizes and other controls over chart labels we see on vector charts (ENC), and text in the status bar at the bottom of the screen.
Preferences, configurations, and set up pages These are pages we interact with often so best to have them the right font size for you. The default may be a bit small from some users, but it is easy to get too big so it is distracting. This is set on menu Configuration/General at the top of the page. After your small change, close and open the program to see the change. Recall cmd+opt+v gets you direct to the chart set up, and you can then go to General from there. My choice for default font is courier, with size just a tweak above mid scale, with the status bar size more like three-quarters scale.
Status bar

The status bar at the bottom of the screen is used to read the cursor location as well as weather parameters from a grib file. Adjust its size at menu Configuration/General

Fonts used on status bar and other text set at the same place. Suggest replace stock choice with plain Arial. Our present favorite is Courier New with font size at 85%. You will need to close and open qtVlm to see the change.

City and Country names & borders This is a base map setting, not part of the vector charts. See the several levels of detail available at Configuration/Charts/GSHHS. Some experimentation will find what best meets your needs. Too much info can be distracting, but knowing what you have lets you resolve that. Recall that cmd+opt+V takes you to the Charts setup page.
National text For ENC chart viewing, turn this on to have the names of charted objects expressed in their native language on the chart itself, else they will appear in the default English versions. When doing a cursor pick of the object, however, the native language object name (NOBJNAM) and the native language information (NINFOR) will show in the pick report, regardless of this setting, assuming the chart has this information encoded.
Important text only This is an S-52 standard ENC display option that nearly all navigation programs have as it is technically required, but it shuts off almost all text and labels, including buoy and light labels and characteristics. Best to keep this option in the off position, unless you do want to simply get rid of all text. With this option turned on you will see only: vertical clearances of bridges, overhead cables, pipelines, and conveyors, plus the names of certain navigation tracks and other lines, and required radio check in channels. Generally we leave this option turned off.
Other text Another S-52 requirement. This turns on or off all the other text on the chart, including essentially all object names. Generally we leave this option turned on.
De-clutter text Is an option to prevent writing of two labels on top of each other on an ENC found at menu Configuration/Charts/Raster and vectors (cmd+opt+v). Turn this on to prevent that, which seems a natural default... unless possibly looking for two different labels for two objects very near each other or two labels for the same object.
Troubleshoot disappearing labels If you see labels come and go as you change the scale, then this is likely due to the de-clutter text option above. Namely, there are two labels possible near each other and on different scales you may get different charts or different positioning that hides one of them. Turn off the de-clutter to read both.. even if they overlap.
bridge and cable clearances These are part of the Base display and therefore always on. Cable clearances are plain numbers such as clr 20.4m. Bridge clearances have the same font and size, but they have a white background: i.e., Bridges have a Background.
1.10 Keyboard shortcuts 
For Mac and PC
PC Mac Executed command
alt+A opt+A Alarms management.
alt+B opt+B Center chart on boat.
alt+C opt+C Show/hide compass.
alt+E opt+E Show/hide labels.
alt+F opt+F Show/hide boats flags (VLM mode).
alt+H opt+H Unlock moving and resizing gauges and histograms on the chart.
alt+I opt+I Show/hide Instruments on map.
alt+K opt+K Close single chart.
alt+L opt+L Show/hide polar.
alt+O opt+O Show/hide opponents (VLM mode).
alt+Q opt+Q Show/hide magnifier.
alt+S opt+S Simulation mode
alt+T opt+T Show/hide tracks.
alt+X opt+X Configuration
alt+Z opt+Z Keep boat's screen position when zooming.
ctrl+B cmd+B Start a batch.
ctrl+E cmd+E Take a screenshot.
ctrl+F cmd+F Search vector chart database for chart objects or attributes
ctrl+G cmd+G Grib display configuration (must have a grib loaded)
ctrl+H cmd+H Open/close balisage SHOM. [Note 4]
ctrl+I cmd+I Gribs information.
ctrl+K cmd+K Open a single chart.
ctrl+L cmd+L Show/hide lights sectors on vector charts.
ctrl+M cmd+M POIs management.
ctrl+O cmd+O Open a grib.
ctrl+Q cmd+Q Quit qtVlm.
ctrl+R cmd+R Reload POIs, Routes, Pathways, and Barriers
ctrl+S cmd+S Save POIs, Routes, Pathways, and Barriers
ctrl+V cmd+V Paste a route.
ctrl+W cmd+W Close all gribs.
shift+drag shift+drag Region select
ctrl+drag cmd+drag Region zoom
ctrl+alt+G opt+cmd+G Show in Google Earth.
ctrl+alt+H opt+cmd+H Unlock moving and resizing LCDs on map. [Note 4]
ctrl+alt+I opt+cmd+I Open Chart information display window.
ctrl+alt+L opt+cmd+L Show lights visible from boat (vector charts only).
ctrl+alt+P opt+cmd+P Open a pick report at the location of the cursor.
ctrl+alt+T opt+cmd+T Show/hide main board.
ctrl+alt+V opt+cmd+V Show raster and vector chart preferences.
ctrl+alt+$ opt+cmd+$ Set display mode to $, where $=A=all, B=base, C=custom, D=detailed, S=standard.
Note 1. If Mac user finds that the Detailed display does not work, then go to System Preferences/Keyboard/Shortcuts/Launchpad and at the top uncheck "Turn off dock hiding..."
Note 2. For Mac use of the function keys below, first go to System Preferences/Keyboard and check "Use F1, F2.. as standard function keys..."
F1 F1 Documentation (online link to PDF Manual).
F5 F5 Sync boat (VLM mode).
ctrl+F9 to F12 cmd+F9 to F12 Store screen display in view (zoom level and position).
F9 to F12 F9 to F12 Restore saved screen display.
Note 3.ALERT! If you find that any of these does not work, then check what other programs you might have open, and then look at the list of shortcuts they use. It could be that they are conflicting....  in some cases the other program has a conflicting shortcut that you never use in that program so you might be able to disable it.
Note 4. On a Mac, cmd+H is a stock command that hides the front window in view when multiple are open; opt+cmd+H hides the back windows. After that, focus returns to qtVlm and control of the instruments. You can also shut off these Mac shortcuts.
1.11 Marks and POI 
and beacons

Waypoints in qtVlm can be made in three classifications: POI, mark, or beacon. Generally it does not matter which you use. The generic POI (point of interest) is the default. There is not often need to change this. This may also change its default color and symbol size, as noted below. The name "waypoint" is also used to refer to any one of these mark categories when it is used in a route or as an active navigation target.

Default options are set in Configuration/General where you can change the font and label sizes. Then under /Colors click dropdown to set size and color of each kind of mark. Size has to be made fairly large to see the differences. Near bottom, Allow POIs to be moved immediately is just that (they have then blue ring around the center), else ring is red and we need to click it to turn it blue, and then move it. To move a POI, drag label, not symbol. See below on locked POI.

Set up a POI
or mark

To set a mark, move the cursor to the place you want it, then right click and choose top item New mark. At this point you can digitally adjust the Lat-Lon, add range rings if useful, lock it so it can't be moved, if desired, or change its category to mark or beacon.

At the bottom there is also input for a Comment, which shows up as a tooltip when the cursor is on the mark—used in a route, it could be something like, " Jones Rock and the church in range,"  or maybe "Expect a northerly to start to veer at this point," etc.

You can also assign an arrival radius to the mark, or define an image that will popup with a cursor over, or activate the mark as the next waypoint when underway or when using the simulator. See individual entries on these settings below.

— Be sure you can see the full POI set up window. These last options are at the bottom, and you may need to scroll the window to see them.

— Be sure to push the OK button top right to save your choices, or press the Return/Enter key.

Backup POI After making a set of marks that may have taken some work, you can back then up with cmd+S or ctrl+S. This step saves marks, routes, and barriers. Also access from menu Marks/Save POI and routes
Marks don't show! You make a mark and it does not show up, or you know you made a mark but now do not see it, then chances are it is turned off with menu View/Show-hide/Show POIs. There is an option to Hide all but the boat and it does just that! You can always check Marks Manager (see below) to confirm your marks are still in the system.
Image on a POI At the bottom of the set up page you can assign an image mark, which will show up with a cursor over the mark. This function can be be very effective. In some cases, we might just drop a mark as a place holder for an image of what this area looks like (find it in Google images or your own photos). Could  be a reminder of what a tricky harbor entrance looks like. Or it could be a picture of a Ferry Schedule!  Can be PNG, GIF, or JPG (will not read alternative JPEG). Can be any size. The result will be actual size up to 300 pixels height; larger images will be reduced to 300 pixels height.
Arrival radius This is used for navigation underway or with the simulator. When following a route or pathway, this radius is how close we must be to the active waypoint we sail toward that will trigger shifting the active waypoint to the next one in the route. The range is set in meters. We can override this and switch to the next with a right click Activate next POI.
POI Route and Pathway options These functions are discussed under Routes and under Pathways.  They refer more to uses of the POI rather than setting it up.
Line between POI You can draw a line between any two POI which has multiple applications. See under Ruler tool and measurements.
Activate the POI At the bottom right you can assign this to be the next waypoint (WP) to navigate to, i.e. activate it. This will override other routes in progress and go to this one. This then links the boat do the mark (now officially a WP) with a line. To undo this, right click the mark, and at the bottom uncheck the Mark to waypoint box. You cannot undo this from the POI set up window.

Any time that wind and polar are loaded, you can move the boat to the vicinity of any POI and right click the POI and turn on a layline display showing sailing approaches to that POI or position you have marked with a POI. With real wind read on instruments you can use that for the reference. With grib forecast you can experiment by moving grib time or the boat to see how the laylines respond. Approaching any mark, it is logical to turn these on so you do not over stand. Current in a grib forecast or forced will affect the location of the laylines.

The heading of a layline is determined from the TWA that gives the highest boat speed at the TWS in effect. Without a route or active waypoint assigned, laylines at a mark are determined by the wind at the boat, not at the mark. With a route or waypoint activated, the laylines from that point will move as the boat approaches the mark if the wind is also changing. With a route defined from point to point, the wind in use for the laylines will be the wind at the dot that moves along the route.

Troubleshooting: if you are navigating point to point with the boat not showing anywhere on the screen, and doing all the above you do not see the laylines show up, then right click the screen somewhere and choose Move boat here. Then you can still do point to point but now the lines should show.

Lock a POI

There is a Lock button in the POI set up window that locks the mark. This prevents it from being moved or accidentally deleted. Recall red ring cannot be moved. Blue ring can. To move or delete a locked mark it must be first unlocked. (The Lock button is not related to the Arrival radius next to it.)

We cannot delete a locked POI without unlocking it... unless you choose Remove from the POIs Manager (cmd+M). If you have several locked POIs to delete, then Remove from the manager window is the fastest way. It overrides the lock.

Move a POI Left click the POI label (which serves as a handle) and drag the mark as needed. If a blue circle appears on the mark when you first click the label, then it can be moved directly. If the circle is red when first clicking the label, then you have to wait a second so till it turns blue to move it. This helps prevent accidental movements. The setting is made in menu Configuration/General/Appearance at the bottom. See note above on locked POI.
Marks Manager Open with keys Cmd+M or menu Marks/Marks management. Many options here, including Archiving (see below), Exporting, Center on, Delete, and more. See video Marks Manager and Archives
Circles  (Rings) on a POI It is often valuable to put one or more range rings (see discussion) on a POI, or on the vessel itself.  On the POI set up screen (right click/New mark) choose the number of rings and the range between each one in the Circles section. You can also choose here the color of the rings. These will then show up immediately on the screen. These range rings are not related to the Arrival radius, discussed above. Rings on the vessel icon are set in menu Boat/Boat settings/Circles.
Archive POI

Archiving marks copies them from the Marks Manager and stores them for later use. There is no "Hide a specific POI" option in the program, so if you want to not see one or more, but not lose them, then archive them and then delete them from the Manager. To use this feature, open the Marks Manager (Cmd+M). See also video Marks Manager and Archives

1) Cmd click (ctrl click on a PC) to select the marks you want to archive. You can also drag to select if they are in order, or drag select and then cmd click to unselected individual ones. Once you have your chosen ones selected…Press Archives button

2) If your target archive is already there select it, if not click New Archive and create one. Then you will see a button called Paste n POIs… where n is the number you had just selected from the main list. Press that button to copy them there.

3) To see what is in each of the archives, double click the archive name

4) After confirming you have moved the marks you want to the archive, then return to the Marks manager and delete them.

5) Note you cannot duplicate marks in the same archive. If you do paste in ones that are already there it will not warn you, but just not do it. You can add the same mark to multiple archives.

6) Once done, you can move marks back and forth. To put one back, open the archives, select the archive, highlight the mark or marks to replace, and press Load in qtVlm.

6) CAUTION: at present there is no warning if you delete an Archive, so be careful. In contrast, if you delete an individual waypoint, it does give you a warning.

Copy a Lat-Lon position qtVlm has a unique way to extract to the clipboard any position on the chart or world base map. Just right click the place, choose New mark, then press Copy on the right. That will put the decimal Lat, Lon into your clipboard to be used elsewhere as might be needed. This is a way to capture a location on the chart, even if you then just Cancel after Copy, with no actual mark being created.

Export / Import POIs


Save / Load

To export one or many POI, select them in the Marks Manager and export as GPX. The you can delete them if you like. To get them back in your program or another one, use menu Marks/Import/Import a GPX file. This will load them onto the chart and into the Manager.

In the menu Marks there is a Save POIs and Routes and Load POIs and Routes. This saves all loaded POIs and routes but nothing else. More important to note is, when you execute Load POIs and Routes it will replace whatever is now loaded with what has been saved. If nothing had been saved earlier, it replaces what you have loaded with the nothing that is stored, ie it erases what you have. Thus we are back to the important guideline to save or export your settings whenever you spend a lot of time configuring the program. This is a subset of the full operation executed from the menu qtVlm/Export qtVlm data and Import qtVlm data. See Saving your set up (backup options).

AVURNAV Near the bottom of the Marks menu, this stands for Avis urgents aux navigateurs (Urgent notice to mariners). Turn this on and it will mark the places in French waters with special notices. The description will be in French (use Google Translate as needed). This is equivalent to the US NGA and USCG Broadcast Notice to Mariners. There is an equivalent US KML file that we could load into qtVlm, but on last check it was not updating properly, so we wait on this one.
Right click POI options

Edit: opens the edit options
Delete: does that.
Not simplifiable: if in a route it cannot be removed in simplification or optimization
Set grib date: If the POI is part of a route, this will set the grib date to the time the boat is expected to be at that POI.
Route: If part of a route, it shows multiple options for interacting with that route. If not part of a route, it says No route, with a dropdown of routes you can assign it to. If you add it to a route it will enter the route at a place depending on the name of the POI and the specification of the route order as by Sequence or as by Alphabet.
Laylines: draws laylines from that mark based on either grib wind at the boat or instrument wind at the boat.

More options
      Copy: No practical function I can discern. May be tied to an earlier relationship with OpenCPN
      Ruler tool: does that
      Draw a grib reckoning: does that
      Center on POI: does that
      Navigate toward this POI: Assigns the type of navigation that will be used toward this POI if added to a route. If already in a
      route, it will let you change the type at this point, which can change the color of the label. Green=VB-VMG, blue= B-VMG
      (VMC), and pink = GC
      Draw/Edit a line to another POI: A handy feature to measure precisely between POIs. See under Ruler tool
      Draw a GC circle to the boat: This creates a circle, centered on the POI and going through the boat that shows all points
      equidistant from the POI. When racing it can show all boats that are both closer and farther from a specific mark than you are.

Mark–>WP: my Boat: Assigns this POI as the active way point to sail toward.

1.12 Google Earth Interface 
Description With an internet connection, you can set a chart display in qtVlm to the region you want to see on Google Earth (GE) and then view that same region in GE. This can help identify landmarks, or we can even capture the image, and use qtVlm to georeference it so we can navigate right on that image if useful, which could be the case in some isolated locations with poor charting. The function will open GE and set the view as you have selected, or very near to it. This requires the GE app be installed on your computer. It does not work with the online version—it does work well with the mobile versions of qtVlm and GE.
Activate Set the screen the way you want it, then menu View / Show in Google Earth or use the keys opt+cmd+G
Troubleshoot If you get an error message that the file cannot be opened by, for example, Adobe Reader, or anything else, then that program, probably installed after GE, has taken that extension, for itself, but it cannot actually read it. Thus we have to reassign .kml to GE. First, search your computer for ".kml" to find a kml file, and if you find one, right click and say open with, and then navigate to googleearth.exe or and then check the box that says always open with this app. If you cannot find one, then open GE, and use the Show Ruler tool in the toolbar to draw a line, then Save it, then find it in MyPlaces, right click and Save As and put it in your downloads as a kml file (choose kml over kmz). Then you have file you can use for this and when done delete it.
Tag a location To ID a chart object or objects on the GE screen, set a mark on the object or several objects in qtVlm, then view these in the marks manager (cmd+M), highlight them together (cmd click for individuals or shift click for a sequential list), then export as GPX. Then show the region in GE as above, and then just drag and drop that GPX file onto GE.  Then these marks will show up on the GE screen in the right place.
Georeference a GE screen cap To be added when we figure out how to export a GE view directly to KML that qtVlm can read, already georeferenced. In the meantime we put two pins on the GE display in opposite corners, then give them a name equal to their Lat, Lon. Then capture the image, load into qtVlm, and georeference. Works well, but there should be a one step process for this.
1.13 Search vector charts 

qtVlm has a unique ability of letting users build a database of chart objects, which can then be searched by name, with the option to filter by object type (buoy, light, bay, river, etc) or even attribute (rocks awash right at the surface, lights that stay on during daylight, etc), and then we can center on the object selected from the list found. We can also limit the search to a specific region, which is important after building a large database covering a lot of charts. Once the database is built, we do not need any charts (we look for object locations on the base map) or we can find the objects on RNC charts.

But Step 1 is we must have ENC loaded over the regions we care about, meaning their folders assigned and checked in Folders section of cmd+opt+V. The chart types can be ENC, both S-57 and the encrypted S-63, or they can be from the CM93 chart set, if those happen to be in use—we do not use these in this course.

Build the database




Delete and Rebuild database when chart folders are added

We can search for a charted object by its name. For this we just need to have the ENC charts on our computer, and assign the folder in Configuration/Charts/Raster and Vector/Folders, which we can get to with cmd+opt+V. Then do cmd+F to open the search window, choose Search in S57s/S63s and then type an object name to find it. Once a list appears, you can highlight it and press Center on chart, or just double click it to center the view on that object which will show with a red outline.

Alternatively, you can look for objects or attributes more specifically by choosing Search in Displayed charts. This lets you filter the search by specific objects or even specific attributes. This function searches charts in view now, even if just a corner of it, or ones you have viewed recently—even if you just looked at an inch of it at small scale. To include charts that are indicated by red chart outlines, meaning covered completely by smaller scale charts, then you have to zoom in enough to see some part of that chart to include it. Ones you have viewed recently will also be included. "Recently" means still in the chart cache (cmd+opt+V), which is typically the last 30 or 40 charts you viewed, depending on the cache setting.

The list of objects presented to you at this stage is not all ENC objects, but just those in the displayed charts domain. Likewise for attributes shown, i.e. if you want to find, for example, all the lights that are on both day and night, we look for Lights with Exhibition Condition of Light (EXCLIT) = 1. This attribute applies only to LIGHTS so we can search just on the attribute, but if none exist, that attribute will not be in the list... and our search is over!

You can pass on the database to other qtVlm users if you like. It should be copied to the qtVlm root folder (Mac or PC). Then they can find all of the objects in it even if they do not have the associated ENC installed—for example, they can have only RNC showing and still find all these objects. Note that S-63 objects that might be in the database, will not search unless your program has a valid license for that specific S-63 chart.

Once you assign a new folder of charts you will need to rebuild the database. Start by deleting it at the top right link "Delete names database" on the Charts preferences page (cmd+opt+v), then do the search and it will ask you to rebuild. (If you do not see the link, make the window wider!) You can remove a folder and the database retains the information, but adding one needs a delete and rebuild.

Access Use menu View/Search loaded vector charts or use the keystrokes cmd+F

Search criteria


Inland ENC

Just searching on a string is easiest. That will find any combo, i.e. search on "house" finds Lighthouse, Light house, House, Schoolhouse, etc. But set to exact and it must be exact, including capitalization. To search by object type, we need the abbreviation (acronym) for the object of interest, i.e., a landmark is LNDMRK. When you select an Object or attribute, it will be explained in text beside it. One trick is search for some generic thing like "rock" to likely get a list of the related objects. A complete list of objects and attributes is included in our book Introduction to Electronic Chart Navigation

Inland ENC use lower case letters for acronyms of objects unique to IENC, thus on an IENC you search for "bridge" and not "BRIDGE." Note too that in the sorting of the list you choose from, lowercase are all at the bottom of the drop down list.

Region Search Use shift+drag to define the chart area you want to search, and then do cmd+F to search just that area.
Real / Int These are used for special searches, because some attributes are numeric only. An ebb current marker, for example, is CAT_TS=2, not "ebb." For this special searching the online object catalogs will be helpful. You may need to refer to an online object catalog to learn the numeric value of a particular attribute value.
Sort results When a lot of objects are found, the headers of each column can be clicked to sort them.

If you cannot find what you are looking for, first search for something you know is there. If that is not found, then you likely need to rebuild the database. See above.

Remember that the sought after object need not be in view on the screen, but a vector chart that includes it must have been loaded and searched for or all your ENCs rebuilt at some time in the past.

If you cut and paste an object name and it cannot be found, be sure there is no line breaks in the name. Type it out or paste to text file to check it. The pasted result will not indicate the break, but then it is not a valid search criteria.

1.14 Depth contours and soundings
Background Depth contours are selected in the ENC chart set up page at  menu Configuration/Charts/Raster and vectors or cmd+opt+v on a Mac or ctrl+alt+v on a PC. Depth contours are a fundamental aspect of ENC, especially the Safety contour. These can be set in meters or feet, changed on the Units page. Choices can only match existing contours in the chart in use. See Depths, Contours, Soundings, and Groundings in ENC Navigation.
Check for existing contours

Right click an ENC, and choose Chart Info, and that will include a list of depth contours on the chart. The underlined one is the one being used for the Safety contour. If the underlined value is in italics, then it is a default safety contour, explained in the background article above.

To choose an existing contour for one of your settings (shallow, safety, or deep), enter a value that is slightly less than what you want to avoid rounding effects. The program will always use the next deepest if if does not find exactly what you ask for.

Shallow contour This is the go aground value. If you cross the effective value of this contour in a simulation, you will go aground. Routing computations will not cross this contour. Keep in mind that it can only be selected to match one of existing contours. If the contour you request is not charted, then it will take then next deepest one. See related discussion in the alarms sections. The COG predictor (or ruler tool) gives a red obstacle warning when the effective value of this contour is detected, which is often the one just shallower than the one requested.
Safety contour

Chosen to be the depth outside of which you have no concern about grounding, This will typically be your draft plus a safety factor (under keel clearance, UKC) plus a correction for negative tides and squat for larger vessels. The COG predictor (or ruler tool) gives an orange danger warning when this contour is detected.

See also Isolated danger symbol

Deep contour Use this contour as you like. It does not affect routing or alerts. See our textbook for examples.

Safety depth
soundings color

Unlike the requested contour values entered for the contours, which may or may not be what gets selected and indeed can change with charts, the value entered here is digitally used as entered. It does one thing only. Charted soundings shallower than this value are printed black; soundings deeper than this value are printed gray. Thus you can set this equal to your requested safety contour and the color of the soundings shows what areas inside the contour are safe or dangerous.
Viewing soundings and contours

Soundings and contours are not part of the Base of Standard display, so they can be turned on or off of any view. They both have a SCAMIN, which means that even turned on, on some display scales they will not show. You can adjust the SCAMIN sensitivity. You can cursor pic a contour to read its value and its SCAMIN. The same is true for any sounding, which is a unique function of qtVlm.

On the setup page you can control the size and density of the soundings. If made larger than about one third the size scale, then at larger chart scales they may be too close to see and can be adjusted with de-clutter. The defaults on both settings seem to work well.

Soundings and alerts qtVlm is unique among many ECS in that it will present an alarm when crossing (by predictor line or cone) a sounding that is shallower than the safety contour. See alarms.
1.15 Changing Region View 
Initial set up

Here we speak of the region in view on the screen, regardless of charts loaded or not—looking at base map only, if no charts are installed. The default location is France. Follow these steps to set the region view to where you want

1) Click the 1:1 icon in the toolbar to show the full world, then left click and drag to roughly center on where you want

2) Then on a Mac, cmd+left-click drag and release to zoom in on the area of interest. On a PC, this is ctrl+left-click drag

3) Once there you can left click drag to pan the chart, use + or – buttons in the toolbar, or mouse roller to zoom as needed

4) Then right click and choose Move boat here, then this will be the view you see if you close and reopen the program

Move to another region

1) You can go to an all new region with the above procedure again, or just drag the base map and zoom manually to set up a new regional view. To go back to where you left the boat, click the COG/SOG sign at the top microboard to center on boat.

2) You can also send the boat ahead to where you want to go and then click the COG/SOG sign to go there. To send the boat, click the microboard to open the Dashboard, then on the Position tab, click Position and type in where you want to go.

Save view set up


Reuse selected regions

Go to specific region

You can conveniently repeat or switch between selected regional views a couple ways.

1) Define and save specific regional view layout with the key stroke cmd+F9 (Mac) or ctrl+F9 (PC). This saves the location and zoom level in view. Then if you change to another regional view, you can return to this one with the F9 key alone. You can save 4 regions this way with keys F9, F10, F11, and F12. Then you can switch between them as you like. The boat does move with these changes. See notes on use of function keys on a Mac in the section on Keyboard shortcuts.

2) For regions visited periodically, you can place a mark at those locations and give the mark an appropriate name, then using the Marks manager, just select the mark and choose Center on mark.

3) If you have ENC charts loaded for the regions you care to visit, you can just use the Search function to go anywhere on those charts. cmd+F on a Mac or ctrl+F on a PC, then type in "Statue of Liberty" to get to NYC or "Port Townsend" to get back to the West Coast where our main training charts are located.

"Dual View" display



You can use the saved views discussed above to simulate a dual view display. Set up one display with the chart and zoom level desired (such as very close in to the boat to see its track build) and save that to F9 as above (i.e., cmd+F9), and then set up a view around the boat on much smaller scale for a look-ahead view and save that to F10. They switching F9 to F10 you see up close and also far off.

You can also use this feature to compare an ENC and RNC for the same area and zoom level. Set up the ENC display you want to compare, then right click and choose Show only this chart, then set the Fn key such as cmd+F11. Then leaving all else untouched, change to raster display, right click and choose Show only this chart, then cmd+F12. Then the keys F11 and F12 switch back and forth ENC and RNC.

1.16 S63 Encrypted Charts 
Background Most nations outside of US offer their ENC in an encrypted format called S63. The qtVlm User's Manual is the main reference for setting these up. There are several steps to the process.
Alert! Ultimately you need to have your S63 charts located in the root qtVlm/S63 folder, but they should be backed up in full at another location. In the set up process, where you assign the location of the charts (similar to folder selection for S57 ENC) there is a button to "Remove." That button deletes the files completely from the root folder; it is not just deactivating them as it is with the S57 counterpart.
Reference The second edition of our textbook Introduction to Electronic Chart Navigation has a Section 1.9 that covers the install process and required folder structure, along with an example you can practice with from New Zealand, who has free ENC in the S63 format.
1.17 NOAA Catalog and Chart Updates 
Background Each ENC we view has a base edition file ending in .000 along with multiple update files ending in .001, .002, etc, which are the updates to the base edition. qtVlm has a unique feature that lets user's learn what has changed in the various updates. This can be valuable, for example, to explain a new buoy or a missing buoy that you were accustomed to. Or changes in the magnetic variation, and so on.
How to access If the chart is already loaded, go to that chart, then right click and choose Show only this chart. Then access the single chart control page with cmd+K (Mac) or ctrl+K (PC), then use the tab Updates, and open the links to see what is new, modified, or deleted. Once you see an item of interest, click down to the lat-lon, and then press Load and Review... and qtvlm will take you to that version of the chart and show the object... even if it has been removed in the latest version. The symbol will be marked with the appropriate update symbols. See this video explanation of this unique function.
Update symbology The Starpath training charts provided with our online course include an interactive ENC version of ECDIS Chart No. 1. The charts are located near Timbuktu in Mali! See Lesson 4. The update symbols are in the top left panel, marked A,B. The symbols are also in Chapter 4 of our textbook Introduction to Electronic Chart Navigation.
NOAA Catalog This is accessed from menu Charts/NOAA Catalog. See this video explanation of this powerful function. Besides download by state, there is also option to download by Region or by USCG district.
1.18 NOAA Chart Files and Notes 
Chart files ENC downloaded from NOAA come in a zip file named by the chart or region downloaded. That unzips to a folder called ENC_ROOT, which contains the chart folders named by the chart names. Inside this folder you find: chartname.000, the initial edition of the chart, plus charname.001, .002, .003 and so on, which are the chart updates. You can see exactly what took place with each update using the qtVlm chart update function. Also you will find several text files: chartnameA.txt, chartnameJ.txt, chartnameH.txt, and so on. Chartnames with a letter. These are the various chart notes for that chart. You can open these and read them here, or as they show up in context in the use of the chart, discussed below.
Chart Notes

On a paper chart, the text of the notes are scattered around the chart in places not to interfere with the chart content. Then at the site of where the notes pertain, there will be a printed label, i.e. See Note A or see Note F, which you then must find and read.

On an ENC there are no such labels. When you cursor pic an object (right click and ask for Vector chart elements) such as a restricted area, if there is a note associated with it, there will be a link to that note in the pic report. Thus most of the notes txt files discussed above are only seen at those specific objects. The exception is Note A, which is a properly of the whole chart, so when you right click the chart and ask for Chart Info you will get a link to the Note A for the chart. These are generally longer notes covering various topics.

If in the ENC set up window you turn on "Highlight objets with extra information," then you will see an [ i ] symbol on the objects that have extra information. The object attributes TXTDSC or NTXTD will show one of these text files; PICREP will show an image; and NINFORM or INFORM will show text info directly, not linking to other files.

2.1 Boat Settings 
Access There are two ways to get to boat settings. For those that are changed more frequently, use menu Boat/Boat Settings. At the bottom of that window is a link Other Settings that takes you directly to a screen with a couple more settings. This latter set can also be reached by menu Configuration/Boat. We use the terms "boat," "vessel," and "own-ship" synonymously.
Vessel icon

The default icon size is set with the slider in menu Boat/Boat settings/Icon size on map.  Mid scale is a large icon; quarter scale might be good starting point. The vessel icon size remains the same size regardless of display scale, unless you choose to add dimensions to the vessel as described below.

You can change the image for the vessel icon at Boat/Boat settings/Custom boat icon. The image you choose will be reduced to about 110 pixels LOA with slider full scale. It will then scale with the slider. The images should be PNG, with transparent background, trimmed right next to the boat, leaving no margins.

If you care to assign realistic dimensions to the vessel icon that will appear when you zoom into scales comparable to vessel dimensions, then you can assign them at menu Boat/Boat settings/Dimensions.  This is the same place we specify the location of our GPS antenna for AIS broadcasts. LOA = A+B, and beam = C+D. After assigning these dimensions, when zoomed out to normal scales, you will see either the default icon or the one you changed it to in the step above, but when you zoom way in to dimensions of the boat, the icon will change to a plain gray generic boat shape, but it will have the dimensions you asked for. The GPS position is marked by a red dot. The yellow dot on the centerline at one third of the LOA from the bow is the turning point when running the simulator.

If you want the zoomed in view of the vessel icon to match a specific vessel type, you can link to a picture of that vessel, using image specs noted above. Use Boat/Boat settings/Image for real size boat. The assigned boat dimensions and image dimensions should have consistent LOA to beam ratios for the best presentation. With a scaled image you can practice entering a marina or interactions with close traffic. It will also offer realistic practice on interactions with obstructions during simulation.

Boat image on Microboard: If you do nothing and leave dimensions at 0, then microboard and vessel icon are the default at all times. If you add a custom boat icon then that shows on the Microboard and on the screen for all scales, and behaves with dimensions as noted. If you then add an image for real size boat, then that is the image that shows on the microboard, but if you have a custom boat icon assigned, then that is the one you see on the chart until you zoom into boat dimensions in which case your custom boat icon switches to your real size boat icon. If you want the same boat for custom icon and for real size boat, then you might use two that are identical except different colors,which would then be a reminder that you have a real boat size icon installed as it shows on the Microboard, whereas the one on the screen has a different color.... or just use the same for both!

To remove vessel size display features, return to Boat/Boat settings/Dimensions and set all dimensions to 0.

Heading line Configuration/Boat/Specific Length for heading line (below Reckoning Style) in meters. 1852m = 1 nmi, 900 m is ~ 0.5 nmi, or choose a longer line. Set to your preference. Some users prefer it to be long, so you see what landmarks or channels are dead ahead. A heading line is crucial so it can be compared to the COG predictor (below) to ensure we are going where we think we are going.
COG Predictor
called "Reckoning"

This display shows where the vessel icon will be sometime later (user selected), plus it will trigger an alarm if crossing any isolated danger or the safety contour, or the coastline when no safety contour set. This tool is a key setting for safe, efficient navigation.

1. Configuration/Boat/Reckoning Style/... We have option of just a line (based on SOG), or we can use the powerful Dangers cone, and chose an angle, i.e., 10°. A cone, even if narrow, helps us distinguish this from the heading line at a glance.

2. Configuration/Charts/... on top line turn on Coast lines from S57/63. Else it will use the base map (GSHHS) boundaries and not know of safety contour.

3. Select extent of cone from Configuration/Boat/Reckoning calculation... use time or distance. "Crank" is a in-house special term for computational step in routing.

NOTE: alarm settings in Configuration/Boat are for instrument readings or NMEA only, not related to the alarms we get here. See more on alarms.

Magnetic vs. true headings

World Magnetic Model (WMM)

Make selection and enter magnetic variation at:  Boat/Boat settings/Variation.  Note that wind, waves, and current directions, and all directions given in an ENC cursor pick report will be in True at all times.

We can also at that location, turn on the WMM computation of the variation, which will then provide an accurate value of the magnetic variation at that time and place, worldwide. (This is a good way to check the values listed on old paper charts.)

To read the WMM value of the variation at any point on the screen, right click and choose Query World Magnetic Model. That will then display the variation at that time and place, as well as the annual change in variation, as well as the dip angle needed for compass card balancing. You can also then change the date to see how it has changed over the years or into the future. The WMM model is updated every 5 years, on the even 5s. In principle ENC should provide the values from the latest WMM.

Range rings (circles) You can add range rings to the vessel icon which are helpful for interpreting the radar screen and for marking minimum distance off. Range rings are called "circles" in qtVlm. Set these in menu Boat/Boat settings/Circles.
Track set up

See under tracks.

Center on boat See Center on Boat
2.2 Instruments 
Basics There are two sets of instruments. One set is for showing on top of the charts and weather data; the other is for a full screen display of instruments alone... maybe intended for distant viewing from a phone or tablet. For our Starpath course work we can shut these off by hiding the "Instruments panel," the right hand dial (black background) on the toolbar. See proposed toolbar set up video.
Display options

Choose which meters to show at Configuration/Instruments. Also there check which ones you want to display a graph of the readings versus time, called a histogram. Histograms take a lot of resources, so use the minimum needed.

Also select default size for all instruments. Note that once an instrument has been moved from its default location, this size default does not apply to that one. Thus to get them all the same size after moving any, choose Reset and then resize. You can also resize as you drag to new positions. You can also Lock all here, but then you have to return to undo that before making changes at Boat/Instruments

Alert: Reset does indeed reset to all on the bottom or side with the same size, and there is no undo nor cancel.

Average readings Menu Configuration/Instruments is where you can average the inputs for boat speed, wind speed, boat heading, wind direction. Also enter there an offset for the barometer (pressure sensor).
On / Off Use toolbar icon with blue outline, or menu Boat/Instruments/Show Instruments.... or use opt+I  (Mac)  ctrl +I (PC)
What shows on instruments See either live NMEA data; simulated data; or data from a replayed file of NMEA data. Each individually, cannot see more than one source at a time.

Route logs

These plots of meter readings vs time are presented as an Instruments option. Select the instruments and histograms you want (see above), then when they are showing on the screen, do a long click on the LED meter to toggle the histograms on and off. . 

This is a powerful feature of qtVlm that is worth practicing with and using. There are many applications, such as watching wind shifts and wind speed, evaluating tacks by monitoring the speed, watching the pressure, monitoring VMC, and many more.

See here our presentation of the various instrument histogram styles available.

Histograms appear in two places: in instruments (see above) and they are also used in the record of a route sailed or computed, accessed from menu Routes/Edit route/(select one) then see tab Histogram. Then dropdown to find the parameter of interest. Click the white border at the top for digital values.

See also meteogram, which is another type of graph used in qtVlm

Lock / unlock Histograms use cmd+H or ctrl+H. For LCDs use opt+cmd+H and alt+ctrl+H. Or Boat/Instruments/Freeze. If you choose Lock all at Configuration/Instruments, then these controls are locked.
Save settings Use menu qtVlm/Export qtVlm data  then uncheck everything but Instruments configuration and say OK. Then in the root qtVlm folder rename the file to and save that file.  *** need to confirm this procedure.
Troubleshooting Exporting qtVlm data from one computer to the next might bring instrument settings that are not consistent with the new monitor display, in which case the layout might not work for you.  If these cannot easily be rearranged as needed, you can use the Reset button and start the layout over.  Find it at Configuration/Instruments and Reset on the second group down.  See Save Settings above.
Reset The Reset button implements all the settings seen to the left of it. If you have made custom locations, this will erase them all and put all meters to the left or bottom of the screen, at the size indicated.
For details... See the qtVlm manual for instrument details and many examples that show what can be done.
2.3 Tracks 

A track is the visible trail left behind the moving boat icon when connected to live GPS or when running the simulator or replaying a file of past NMEA signals. Use of the track is fundamentally important to safe, efficient navigation.

The base control is under menu View/Show-Hide/Show tracks where tracks are turned On or Off, also activated with opt+T or ctrl+T. Some of the track controls can only be accessed when [tracks on] others only or best done when [tracks off]. There are several parts of the program that influence how the tracks appear and behave.

Track color and line thickness [track off]

Set at Configuration/General/Colours... drop down to Track. This should be changed only when [track off]. If you make the changes while [track on], they will not appear, but when you stop and start again you will get the new settings, but will have lost your past track.

Track accuracy, length, and auto save
[track off]

Set at Configuration/Boat/Track... Recommend Very High accuracy, unless open water or ocean sailing where less is needed, Max length usually No limit. With a limit it is often called a "wake," and at 6 min the length is one tenth of your boat speed; at one hour it is your boat speed. Auto save definitely valuable when underway; less so when training in most cases.

When viewing track properties you see the length of the track, its duraction, and the number of data points in it. The density of points is contolled by settings noted just above.

Show / Hide [tracks Off or On] IMPORTANT. In menu View/Show-Hide tracks must be turned on. This will hide the track no matter what other settings are on. Likewise, View/Hide all but active boats, will also shut it off. Use View/Show all or View/Show-Hide to turn the track back on.
Main controls start at menu Boat/Tracks

—Pause track
—Activate track tooltip (shows wind and vessel performance)
—Start new tract (or use micro board Reset Track)
—Archive present track (leads to a series of options)
—Export current track. Default format is GPX. You can change extension to CSV for additional wind data (POL, PCP), or KLM to show on Google Earth
—View Archived tracks.

Convert a track to a static route

Export track as GPX, then import from menu Routes/Import Route/ In GC mode. The track imported as a route will be permanently locked (frozen), so it cannot be edited or activated. Hide or show it from the Edit menu.

Tracks and polar improvement Tracks are crucial tools for improving your boat's polar diagram. When sailing underway, the track of the vessel stores all the wind and vessel performance data including PPC, the percent of polar speed achieved. After a sail in varying conditions you can export the track as CSV and then analyze it to detect how well you are meeting your target speeds and as needed modify your polar diagram data,
2.4 Alarms 
Types of alarms

There are several types of alarms that can be set in the program to enhance safe navigation, or just to alert you of certain conditions. When underway in real time or with the simulator there are a set of AIS alarms that can be configured that warn of interactions with approaching vessels, and there are also alarms that warn of hitting rocks, wrecks, or other obstructions depending on their soundings, which can also be represented as an isolated danger symbol (also depending on their sounding relative to the requested safety contour), and there are alarms when crossing the safety contour, the shallow water contour, and the shoreline. These latter ones are triggered by the COG predictor line or cone. These predictor alarms are also indicated with the ruler tool (see below). There are also alarms for dragging anchor, approaching an active waypoint (arrival radius), or radio check in zones.

In addition to the alarms for interactions with charted features, you can define open or closed barriers that will trigger an alarm when crossed. There are multiple uses of this feature: in routing you can block directions or areas you do not want to cross—a routing computation will not cross a barrier—or you can use them like a danger bearing line to keep you away from hazards underway.

Another category of alarms are those indicating specific values read from sensors in any of the instrument displays, such as loss of GPS signal, user set true wind angle limits, or low atmospheric pressure.

See also Details of predictor alarms.

Turn on Alarms

Turn on

Use the toolbar alarm icon, a white bell in square that has 3 colors: green means alarms are on but none is triggered; red means at least one active alarm is triggered; and blue means alarms are off. Shut the alarms on or off with the button at the top of the Alarms manager window, and be sure to press OK at the button. You can control them all with the top button, or set them individually with the buttons below.

Must have coastlines turned on the S57/S63 in the ENC set up page: menu config/Charts.. top line, left. The pathway safety check will also not work if the coastlines are not on.

Alarm levels Alarms from the COG predictor line (or ruler tool) are in two categories: danger being an orange warning or obstruction being a red warning. The idea is that a danger is an alert, such as crossing a safety contour, whereas an obstacle means likelihood if not certainty of grounding, such as crossing the shoreline or zero tide line (green area).
Test alarm triggers

The Ruler Tool is an excellent way to determine which objects trigger which alarms. Turn it on and sweep over the area to see what triggers what. This is also a quick way to confirm that the alarms are engaged and working as expected. See the predictor alarms definitions to learn the triggers.

The anti-grounding cone (dangers cone) assigned to the vessel is an even more effective way to learn about the alarms. Set up the cone at Configuration/Boat/Reckoning style then move the boat to a place you want to test, then start a simulator and turn the boat to sweep the cone over potential targets. You choose the width of the cone (15° is a starter point) and the length of the cone is determined by speed and the reckoning time.

2.5 Danger Cone / COG Predictor 

Also known as an "anti-grounding cone," but it is much more than that. The COG predictor line (reckoning) shows where the vessel will be located at some time in the future depending on boat speed and reckoning time interval, which is a common configuration, as opposed to looking at some fixed distance in front of you. A common set up is to look 6 min ahead as then the predictor line length will be one tenth of your boat speed. This is a dynamic setting. Sometimes we look 6 min ahead, other times 60 min ahead, or when docking maybe 1 min ahead.

The predictor line triggers an alarm when it crosses a hazard so that it alerts you before you cross the hazard. The dangers cone just fans this safety test out from our bow as a cone to detect hazards to either side of our track, not just right on it. It is a powerful, must use tool, in hazardous or close in shore waters.

If the cone is not used, at minimum, the predictor line should be used in all waters just to show where we will be and when, along with the bonus of monitoring for hazards ahead. The various triggers covered are detailed elsewhere.


1. Configuration/Boat/Reckoning Style/... turn on Dangers cone, and chose angle, i.e., 10°.

2. Configuration/Charts/... on top line turn on Coastlines from S57/63. Else it will use the base map (GSHHS) boundaries, which are not as precise, and it will not know of the safety contour.

3. Select extent of cone from Configuration/Boat/Reckoning calculation... use time or distance. "Crank" is a in-house special term for computational step in routing.

4. NOTE, alarm settings in Configuration/Boat are for instrument readings obtained via NMEA sentences (sensor inputs).

Isolated danger symbol Rocks, wrecks, and obstructions that are outside of the displayed safety contour that have a sounding less than the requested safety contour value are assigned a prominent magenta symbol with a transparent X in the middle.
2.6 Simulation 
Position boat

With the place you want the boat in sight, just right click that place, and choose Move boat here... or if the boat is in view but not where you want it, just grab it and drag to the position you want to start from.

For a specific Lat Lon with the boat in view, right click the boat and choose Set up position. You can center on the boat (to find it) with a click of the COG-SOG panel at the top of the microboard.

Or regardless of where the boat is or where you are looking, you can click the microboard to open the dashboard, and in the position tab assign the location you want for the boat. The boat will then be placed there, but you might not be seeing it. Click the COG-SOG panel to center on it.

Wind required for sail simulation

Using gribs,
note the start times.

qtVlm is unique in that you can do realistic simulation under power or under sail. For sail simulation we need a polar diagram (there is a default one loaded, which you can change as desired) and we need wind. The wind can be fake (see below), meaning we just, for example, assign it to be 12 kts from 305 over the full chart, alternatively we can load a real or archived wind forecast from a numerical weather model prediction in grib format. The program has several ways to do this. See Weather section.

A quick way to get the latest forecast is just shift+drag to select the region you plan to sail in, then right click and choose VLM partial grib. The wind instruments will then read the correct corresponding wind data during simulation. The region selected need not be precise and can be small. The process loads 5-days of wind forecast over an extended area, starting with the most recent available. Once this has been done, you can subsequently just click the earth icon in the toolbar with the arrow on it to load wind over the region shown on the screen and beyond.

Note that the simulator assumes you are working with such a recent wind forecast that includes the present time, because the default starting time for a simulation is the present time—the time you read on your computer converted to UTC. It then proceeds in real time from there.

If you want to do a simulation in an outdated wind forecast, as we do sometimes in our online course, or you want to start at a time later than now in the present forecast, then you must force the starting time as explained below using Boat/Settings/Navigation Simulation mode/ Force starting date

Polar required

We need to have polar diagram loaded for sailboat simulation and for powerboat simulation—we do not really need this when the engine is on, but since the program goes seamlessly back and forth form engine on to off it is required. There is a default polar loaded for a classic 40-foot sailboat, so this is never an issue. Under simulation, your boat will sail the speed determined by the polar diagram for the true wind angle (TWA) and true wind speed (TWS) you are in. To change speed, change heading to get a new TEWA. Or from the dashboard, turn on the engine and set engine speed.

You can add jitter to the wind speed and direction at menu Boat/Settings/Navigation Simulation mode/Randomized wind if you might want that level of realism.

Speed control under engine Turn engine on and off and control engine speed in the Dashboard Position panel. This engine control does not show until you start the simulation. This control overrides what is set in menu Boat/Boat settings/Engine and Tack-gybes. See notes below on Sail or Engine. Note you can go backwards by reducing speed till it goes negative.
Change course Use slider under Microboard to set rudder; return to center with the yellow button under it. Note that if you add dimensions to your vessel (Boat/Boat settings/Dimensions) and you zoom in to see the true size of your vessel for docking or to study closer vessels interactions, then you will see that the vessel turns about a point one third back from the stem, but the GPS track follows the location selected for the GPS. See this detail in action in our video on the grounding of the Ever Given in the Suez Canal.
Sail or Engine

We can simulate pure sailing or pure engine or any combination  Check in menu Boat/Boat Settings/Engine and Tacks&Jibes which is where we specify when the engine comes on and at what speed when doing a route or routing. This is a crucial setting is effective in simulation if you do not have the engine turned on in the Dashboard/Position tab. For simulation it is best to just set this to 0 kts and 0 kts (always sail), because we can turn the engine on any time we want and control the speed with the Dashboard/Position controls. In short, this control is more for routing than simulation. If you want pure engine simulation, just start the simulation and then in the Dashboard/Position control turn on engine and set speed.

Initial heading

Starting from scratch, the initial heading when you start the simulator will be head to wind in the grib wind of the assigned start time, or if that is not set, then it starts headed into the wind direction at the present live time (Now). Note that this will be true, even if you have moved the slider or grib time off of Now looking at some earlier or later wind. If the boat does not start head to wind, then press Now. After running for a while, and stopping, and then starting again, the initial heading will be where it was when you stopped the simulation.

If head to wind you find yourself with a notable speed (not possible from sails) then check Sail or Engine setting discussed above. Head to wind is 0 sailing speed, so that setting can turn on the engine and set the speed. Also check the Dashboard/Position panel, which is a place the engine might be turned on.

You can turn at speed zero! It will be slow, but you can indeed turn the boat when the speed is zero, which is difficult if possible at all in a real boat, since we usually need water over the rudder to turn. This simulation feature helps get you set up for some practice exercises starting near shore. Think of yourself pumping the sails or using a paddle to turn!
Change active waypoint You can use Go to waypoint (green target icon in the toolbar) while the simulation is running. In fact, any existing POI can be assigned the active waypoint. Right click the mark, and select bottom option Mark to waypoint: my boat. Once an active waypoint is selected, then the meters for VMC, CNM, DNM will populate.
Start time

As noted above, the simulation start time defaults to the present time (Now). You can do simulation at other times in the future or in the past, but then you must force the starting time in menu Boat/Boat Settings/Navigation Simulation Mode. (You can also there choose to impose random variations on the winds from the grib file.) Data from the past can be actual forecasts that you have saved from a past time, or you can use re-analyzed historic data (such as ECMWF) that you obtain now. For extended runs in the future you can use the 16-days forecast from GFS or NBM or use the Climatic Forecast System that offers wind, pressure, and current out 6 months!

To start at a later time than now in the present wind forecast, force that time, and it will run, but if you had been running earlier in that forecast, it will extend the track to the new time on the previous heading. To reset the track, use menu Boat/Tracks/Start a new track, which will give you the chance to archive the present track.

If there is any question about start time, you must stop the simulation to change it

Start simulation Use menu Boat/Navigation Simulation Mode  or use keys opt+S (ctrl+S, PC) to start or stop the simulation. When you start a simulation check that the yellow dot is on the polar curve viewed in the dashboard polar. If not you may have the engine on (position tab) or have forced the engine on in Boat/Boat settings/Engine and tacks.
Center on boat To keep the boat in the center of the chart as it moves, meaning the chart moves under the boat instead of the boat moving across the chart, use the Center on boat option.

When you pause, the boat doesn't.

Stop or anchor.

When you stop or pause the simulation with opt+S or using the boat menu, the simulation is gone from the screen, but the boat keeps going behind the scenes, just as if your were viewing it. Start it up again, and you will see where it is. Forget it, and come back tomorrow, and you will find your boat in a foreign land. It will sail on, or motor on, until it runs out of wind data or runs aground. To prevent this, and pause the simulation where you want it to end, do what you do in life: stop the boat or anchor it, before stopping the simulation. Set engine speed to zero in the Dashboard/Position control is one way. The anchor tab is in the Dashboard, but you must be within 500 m of a coastline in order to drop the anchor... or turn head to wind, see below.
Pause the simulation To pause keeping the boat at the same location, you can turn on the engine and set speed to zero, or you can turn head to wind, and note the SOG is zero before quitting. If there is current present, either forced on in a grib forecast, then you will have to motor into the current to stay in position. Also if the wind is changing directions with time at the boat location, it can start sailing again. Have to look out the window once in a while to see what is going on! 
Start over or start New To start a new simulation at the new present time at a new location, just stop the simulation and drag the boat to the new location and start again. It will then start from scratch at the present time.  If you want to repeat exactly what you just did, you will have to force the time, since that started in the past. Keep in mind that if you save the track periodically or before you quit, you will have a very detailed record on that simulation. See tracks.

Simulate in
fake wind
fake current

Once you have any grib forecast loaded, which is required to open the grib config page (cmd+G, ctrl+G), and on the correction tab you have the option to Force a constant wind across the full screen and then do you simulation in that. For training on how the instruments respond, this can be a useful tool.  That can be expanded by Force a constant current over the region from the same location.
Live AIS

Part of the reason the default starting time for any simulation is the real clock time on your computer is that qtVlm is linked to live AIS targets around the world. Thus once you start a simulation, anywhere in the world, you can turn on AIS and see these targets appear (live real traffic broadcasting their live AIS data), and you can then interact with them via the various collision avoidance tools in the AIS function. Read about these options under AIS. There is also an extended discussion in the Manual on AIS.

If you choose to start a simulation at a time other then Now, then when turning on the AIS you will still see live traffic from Now, but you will be sailing in wind (and other grib data) from the date and time you chose to start. The ages of the reports shown will appears as if you are in real time with them. The only difference is your wind is on a different clock and calendar. In short, there is no such thing in play as historic AIS or forecasted AIS.  The AIS traffic does not know that you are pretending that the wind you sail in is from a different time and date.

Course up versus north up chart display

Once we get to simulations where we have an active, controllable boat heading, we have the option to leave the chart in the default north-up mode, where the chart remains fixed and the boat and its heading line turn when we change headings, or we can switch to course-up display that keeps the boat fixed, headed toward the top of the page, and then the chart rotates around it as the vessel turns. Turn this option on or off with the green toolbar icon. Choose how the screen orientation updates following vessel turns from the Configuration/General/Appearance/ Course up mode page, at the bottom. It can be every so often in time units or in number of degrees turned, or both.

Without simulation, this choice is mute in that the boat then points north at all times. In real navigation this can, of course, also be used if desired.

Simulated soundings The simulator running with vector charts (ENC or CM93) knows the depth area it is over at any time and can display on the depth instrument a simulated depth. The depth shown will be the average of the two depth contours that define the depth area below the boat. Thus the histogram of the depth meter will show a step when crossing a depth contour. The meter will also show isolated soundings or soundings on a charted obstruction. The point below the boat is defined as  ± 10 meters from the location of your GPS receiver on the boat as specified in the menu Boat/Boat settings/Dimensions or  ± 0.5 cm on the display screen you are using, which ever is larger. See related blog post.

A grounding occurs that stops the simulation whenever the vessel encounters a red obstacle alert, which occurs at certain obstructions and at the effective shallow water contour. See discussion the alarms section. In the 4-color option, there is a color change at the displayed shallow water contour, but the grounding more likely occurs on the shallow water side of that depth area. There is an option to put labels on the contours. See related blog post.  See also Depths and contours.

To have the alerts, groundings, and routing restrictions work properly in the program, we must have the coastline detection set correctly which is done on the ENC setup page. If this is shut off, then the coastlines are defined by the borders in the base map, which are not nearly as accurate, and we would sail over or route over other shoalings as well. Likewise, assigning these to an ENC without it being loaded has the same effect. In short, any sensible use of the alarms calls for a loaded ENC.

Cannot change things when simulator is running If any change you apply or ask for does not work, i.e. color of track, then stop the simulator, execute your change and start again. Many settings cannot be changed when running... although some can. You can, for example, turn current on or off using menu Grib/Grib configuration/Corrections controls (windsock toolbar icon). You can also change reckoning types and look ahead times.

If simulation does not run...


— Be sure you have a grib and a polar, even if under power only. Note an attempt to load a new polar that fails, can leave the system with no active polar, which in turn can block simulation.

— Grib time and simulation time must be consistent... even if you are under power not using the grib

— Check menu Boat/Settings/Navigation Simulation mode/ to be sure stimulation start time is right. The start time is Now (present grib time) unless this is set to override that time. Need to stop the simulation to change this.

— Remember default start time is Now, real time. You can have a grib file loaded, with wind showing that you loaded maybe yesterday or earlier, and you can move the slider around and see the wind move... but the time on the far right is in the past. This wind is not adequate for a simulation because it is outdated. The only way to run with this wind is to go to Boat/Settings/Navigation Simulation mode/ and force the simulation start time to be within the time frame of that grib file. Recall that qtVlm offers live AIS during simulation, so it has to keep track of these times carefully.

— If all seems right but still simulator won't run, look for small anchor icon on the vessel. If you had run aground at any point, in view or not in view, this will appear, and it will need to be removed in Dashboard/Anchor/Remove.

—If you try a command or to change settings and it will not accept the OK button, then you have to exit simulator to make the change.

— If simulator turns on but cannot change course under sail, then maybe the boat is outside the grib wind field. Turn on the grib to confirm.

— If things are bouncing around too much, check the jitter settings at Boat/Settings/Navigation Simulation mode/Randomized wind

— If simulator starts but will not move, then check that you have a grib, a polar, and are in the right time frame, and also check that you do not have simulation time set to start at some other time Boat/Settings/Simulation/ Set start time

2.7 Setup GPS / NMEA 
Background You can connect GPS signals from a USB or Bluetooth live GPS receiver or from a wifi signal. The former are called Local connections, the latter are called Network connections. You can also run the internal simulator that creates NMEA sentences or use an external simulator connected to the program (usually) by a network connection. Alternatively, you can execute a file of NMEA sentences that will run as if real data. Other sensor signals such as wind, knotmeter, barometer, heel, heading, sounder, can be added as NMEA signals.




Reading and recording NMEA data.

Use menu Configuration/NMEA connections/Incoming. After your signals are turned on from the GPS device, for USB or Bluetooth, turn on a serial port and in the drop down you should see your signal source. Select it. Turn on Display raw NMEA data, and OK. Other settings can be left off. Once you see your signals coming in, you can close the raw NMEA data window.

Then show Dashboard, choose NMEA tab, and start NMEA. A window should appear showing the incoming sentences. If not the signals are not getting to the computer. See our video on NMEA connections for details.

If you want to capture the NMEA signals to play back or study, note that the window starts saving from scratch each time you open it, and then it stores continually, up to 6,000 lines of data. After 6,000 lines of data it deletes the first 1,000 and keeps adding on. After closing the window, you can restart it without interrupting a simulation or NMEA on run by going to NMEA config window and turn it off (it will already be off) and then OK to close the config window, then open it again and turn on the show Raw NMEA data, and say OK. Note that if you want a playback file, it is simplest to just turn on the save NMEA option. Then when you end the simulation or NMEA on period for any reason, you will find the archived data file in the root folder in a folder called nmeaRecords.

To replay the data recorded in qtVlm or from any source, just turn on the replay file option in the NMEA config page and point to the file. You can control the speed of the play as well as where within the file to start or stop using slider options.

2.8 North-up or Course-up 

Chart orientation




Many navigators prefer to run always with true north at the top of the screen, a chart display called north-up. In this display, when you turn your real boat or a simulated boat, the boat turns on the chart but the chart does not move. In north-up display, when comparing what you see looking around you with the chart, you must first orient yourself on the chart in the direction of the boat's heading at the moment.

Alternatively, you can choose a course-up display, in which case the chart is rotated such that the top of the screen is the direction the boat is headed at the moment. In this case, when you look to the right or left at the water, you can compare it directly to what you see to the right and left of the vessel icon when looking at the chart.

Change display modes The default is north-up. You change to course up with the north-up toolbar icon . Click it to get a yellow course-up icon . When not simulating or running live GPS, you see no display changes when changing this, but there is a notable rotation of the chart when simulating or running live GPS. Note there is no menu option for this display change, so if the icons are not showing, go to menu Config/General/Toolbar and turn on the North-up/Course-up icon.
Course-up controls The controls for how the course-up display works underway are found at the bottom of the page at menu Config/General/Appearance. The alignment of the chart with your heading can be checked and adjusted after some selected number of seconds, or after the heading changes by a certain number of degrees, or both.
3.1 Pathways 
Ways to use the Pathway function

A pathway is a saved series of marks, each having a Lat, Lon, and name. It can be used to:

Use 1. Measure distances between points or along a multi-leg path, or

Use 2. Draw lines on the chart to solve piloting problems, or

Use 3. This is the main purpose of the Pathway function. Make a navigation pathway of waypoints that can be followed or exported as a voyage plan (pathway plan) to be printed, or converted to a route or routing. A pathway planned as a course track can also be checked for the safety of the route relative to charted hazards and obstructions using an automated Pathway safety checker—called in some apps a "route checker."

A pathway can be just two points (a line) or very many points spanning hundreds of miles or more.

Difference between a pathway and a route

A pathway is a static series of waypoints, without a specific means of propulsion assigned to it. We can assign a starting time and once created we can assign fixed speeds to each leg in the Information tab, but there is no interaction with environmental parameters. Pathways do not know about wind, current, or waves. Changing the wind or current does not change the Pathway plan. 

In contrast, a route is a series of waypoints specifically tied to the environmental parameters. In a pathway you go from A to B in a direct straight line. In a route the track will depend on wind, polar diagram, current, and motoring on rules.

Presets A couple presets expedite the set up of all pathways: Configuration/Routes/Default options... turn on Show intermediate POIs and choose POIs by Sequence number. Also in Configuration/General/Appearance at the bottom, turn on Allow POI to be moved immediately.

Create a
generic setup


Create a pathway


For all applications we take these steps, which we use for most pathways. The text description is below. We have a videos on the process: Pathways in qtVlm, Part 1. Part 2 to be added shortly.

i) Start at Menu Pathway/Create a pathway

ii) Give it a unique name. For a quick pathway this could be just "dddd," but in some cases a logical name is better.

iii) Note in the next step you can come back later and change color and line size if you want to.

iv) Set start option to start at Fixed date. (For Use 3, we will enter a time and date, but for Use 1 and 2 this time does not matter.)

v) Choose start From 1st mark. (For Use 3 we might start at the boat, but for Use 1 and 2 we need 1st mark, which is first POI.)

vi) In Options: Turn all options Off, and check POIs by sequence number.  (We will come back to the Export GPX option later.)

vii) Click Append POIs... which takes us out of this window and onto the chart with a now active left click. 

viii) Left click the chart in sequence to layout the pathway. To add a POI to a place that is just off the screen, use keyboard arrow keys to move the chart on the screen—or use the on screen arrows at the top middle of the screen. When done, click the Stop append POIs in the center top of the screen, or just press ESC.

ix) You can also make a series of marks with appropriate names ahead of time, and then when you Create a pathway and start Appending POI, just click the existing first mark of the desired pathway. The first one will not indicated anything, but the next and subsequent marks you click will fill in the lines between them.

To move a POI, click label, not the symbol. Recall POI move properties. You can also right click the pathway and add a POI (prominent green plus sign).

Once done, put cursor on a leg to read: leg number/total legs, leg length and heading, total length along the pathway / distance made good start to finish

Pathway from a series of POI Besides the method above of appending and clicking to add, you can also create a pathway, name it, and then in the Management and Information tab just add the POI sequentially, including inserting, or deleting POI.
Use 1,
measure distances
Make a pathway called, say, MyRuler, then Append two POIs, maybe called Point A and Point B or take the default names. Then just move the points to the places you care about and read the range and bearing directly as you move one, or tool tip on the line after you stop. You can also right click the line, Edit pathway and Reverse it to get the other direction. This has some applications, but there is always the Ruler tool, which can be from a random point or from a given POI or from the boat.
Use 2,
solve piloting problems
We have numerous videos on this application. It is essentially just drawing lines as in Use 1 and using them to solve piloting exercises such as a crossed bearing fix or range and bearing fix. Rings on POI are also used for piloting solutions.
Use 3,
make a pathway to navigate
In this application we can convert the pathway to a route or use the Export Pathway Plan (see below) to get what is often called a voyage plan or route plan.  For this you  select the series of waypoints, give each a sequential number and name, and save it the pathway—done automatically when you end the appending. These applications then call the pathway from the list of pathways.
Create from a list of POI This is done from the POI set up window. See description in routes section.
Check the safety of a pathway This important function checks the pathway for any collisions or close encounters with hazards along the path, such as rocks, wrecks, obstructions, and shoalings. It is turned on with menu Pathway /Edit pathway/ Safety check, at which place you set how far out on each side to look (maximum distance) to look for hazards, and what is the minimum distance off you will accept as safe passage. Recall the color conventions on alarms. See also this video on Pathway Safety Checks.
Select a pathway Move the cursor onto the pathway until it highlights by going bold, then right click for several pathway options.
Order and Reverse To change the direction, right click, edit pathway, and on bottom right, set Reverse. It is valuable in most cases to order the POI in a pathway sequentially (our recommended default); if not changing a name can change the pathway completely.

Export as GPX

Export as QPAR

This is done from a button (Export GPX) on the Edit pathway, Parameters tab, bottom right. This creates a GPX file in route format that can be loaded into essentially any navigation program.

A different option in menu Pathways/Export saves the pathway in the qtVlm format (.qpar), which is unique to this program. These can be archived and then loaded back into the source version of qtVlm or any other computer or mobile version of qtVlm.

Delete a pathway Can be done from the pathway menu or by right clicking the pathway on the chart. After deleting a pathway, all of its POIs remain; use shift+drag to select the area that includes them, then right click to delete all at once.
Hide a pathway Right click the pathway to find option Hide Pathway. This will hide the line and the waypoints.  Or use menu Pathways/Edit pathway/ then find option to Hide pathway and all its POIs.  Or you also have the option to then unhide it here, or just Hide or show the intermediate POIs.
Pathway Plan
Route Plan
Voyage Plan
These are optional names for a printed table that describes the pathway or route. It serves as a record or backup to the travel. Typical content is waypoint number and name, Lat-Lon, range and bearing to next, and with an estimated speed made good (SMG) entered for each leg along with a start time you can have time on leg plus ETAs. Get this from the Edit pathway, where you can enter the start time, then in the Information tab you get a summary of the route, and option to enter an estimated SMG for each leg.   Then Export Pathway Plan to get a CSV file of the table that can be printed.
3.2 Polars and VMC 
What it is

A "polar" or polar diagram is a graphic presentation of the expected boat speed of a sailboat under sail at specific true wind angles (TWA) and true wind speeds (TWS). The data can be presented as a table as well as a graph. Design values are provided by the yacht designer, which serve as a starting point for actual measurements. An accurate polar is crucial to producing an accurate sailing route. A slightly wrong polar can lead to a significantly wrong route!

Format qtVlm can import polars in the .POL or .CSV formats, with the latter using semicolons, not the normal commas. The line enders must be CRLF (carriage return, line feed).  See Introduction to Polar Diagrams and Optimum VMC.
Load a polar

(1) Use menu Boat/Boat Settings/ Polars...

(2) If previously loaded you will see it in the dropdown list on the left to select for use, else load from your own file (Import polar) or choose from the qtVlm polar library (Polars server). The Delete button is to remove the one selected from the dropdown list. There are also numerous other sources of polar data, keeping in mind the format notes above.

(3) When a polar has been loaded successfully you will briefly see a notice that the winds are being computed. Else an error msg.

Read a polar To read a boat speed at a particular true wind speed and true wind angle

1) menu Boat / Polars / Wind polar analysis

2) confirm from title bar you have the polar you want. This is a polar plot of boat speed vs true wind angle (TWA) with dead ahead (top of the plot) being TWA = 0 and dead astern (TWA = 180) being at the bottom of the plot. Boat speeds are depicted as rings of increasing speed.

3) in the top right field enter the ture wind speed you care about, ie 10 kts

4) with the mouse cursor click the screen inside the polar curve and a blue line will appear.

5) watching the outside TWA scale as well as the digital read out of TWA on the right, set the blue line to the TWA angle you care about, such as 105º, and then estimate the boat speed from the nearest ring or read it digitally on the right, presented as BS = 10.03 kts.

View a polar

Big polar

Dashboard polar

Mini speed polar

Big polar. Use menu Boat/Polars/Wind polar analysis...  to see values at any wind and angle. You can do digital interpolation of both: set wind speed, then click the diagram, and drag the blue line to the TWA of interest. This is a big view with excellent interpolation.

Dashboard polar. You can also get a "live view" of the polar and your place on it from the Dashboard/Polar tab during live sailing or simulation. Other than live sailing and simulation, the Dashboard polar can only be used to read TWA at the boat position for the displayed grib time. For other grib times, the read out is not useful. The Dashboard polar is primarily for live sailing and simulation.

Mini speed polar. You can display a mini speed polar anywhere on the chart, or pin it to the boat, a route, or a waypoint. It is turned on and off with menu View/Show-hide/Show-hide speed polar. This speed polar is optionally linked to the compass display. Once turned on, you can move it around the chart or choose to pin it down using the compass controls: right click anywhere on the chart and choose Compass/Center compass/ and then choose boat, waypoint (WP), or a specific route. This pins the compass to those locations and if you have the mini speed polar showing it will be there as well. Likewise you could go to the View menu and hide the compass leaving only the mini speed polar. The mini polar might help interpret a grib reckoning.

The size of the mini speed polar is determined by the reckoning time. If that time is 6 min, then a ruler tool from the boat measures the expected speed at any wind angle (STW = 10 x ruler length; at 12 min , divide by 2). The ruler tool can then be used to determine expected speeds at other specific headings. Underway or in simulation you can get this information more easily with the dashboard polar, but the mini still offers a graphic view of all headings, port and starboard.

Must have a wind grib loaded to see the speed polar, as it is the wind direction that orients the polar diagram.

Edit If you have data from other sources or your own measurements (see below) you can edit the polar from menu Boat/Polars/Wind polar editor. Alternatively, you can compile your new data in a spreadsheet and enter it as a new polar.
Improve polar with your own measurements When sailing, load your base polar, then reset the track and proceed to sail in as many points of sail and wind speeds that you can, turning up for best performance on each heading. At the end of the sail, archive your track and then export it. The track records normal navigation data plus TWS, TWA, STW and the polar wind prediction for those conditions (POL) and the percent of polar that you actually achieved (PPC), which is equal to (STW/POL). If PPC is under 100% you were not achieving your polar speeds. For this important study *all* instruments must be carefully calibrated: AWA, AWS, heading sensor (CTW) and knotmeter (STW).
Limit TWA or scale values See notes under Routing to limit the range of wind angles or scale the values in the polar.

Low and high winds and angles

If your polar does not have low winds or high winds or high angles, qtVlm will interpolate these data. qtVlm implicitly adds a 0 TWS column and a 0 TWA line if missing, with zero values. It does not do it at the other ends (TWS and TWA), however, so if your polar stops at 150 TWA if will use this for 180 TWA, and if it stops at 20 TWS it will take these values for 40 TWS.


Pink Arrow
on the microboard

Velocity made course is the speed you are making good in the direction of the next mark (CNM). It can be computed from VMC = SOG x Cos (COG - CNW). Once a waypoint has been selected as the next mark, the direction to that mark shows up on the compass ring around the microboard as a red arrow. Turn the boat till the bow of microboard boat points in that direction and you are headed to the mark. But that we can see other ways as well. More valuable is the pink arrow on the ring that marks the heading for the optimum (fastest) VMC to that mark. The article Introduction to Polar Diagrams and Optimum VMC discussed the use of that arrow, plus running a histogram plot of VMC as you change course on either side of that prediction. In principle, that pink arrow also accounts for current and waves if you have the grib data loaded and the wave corrections assigned.

The route option called BVMG (best velocity made good) is another way to say best VMC. In rough terms, that route tacks or jibes to keep you on the best VMC to the destination based on the exiting conditions the boat at each crank step. The grib conditions are indeed updating with each crank, but it is never looking beyond the moment. Over a longer run it is more important to look ahead to see wind farther down the course, which calls for a routing solution.

3.3 Grib Reckoning (DR) 
What it is

This unique function carries out a DR computation under sail taking into account the boat's polar and the grib wind and current forecasts loaded. It can be started at any POI, or at the boat, or at any other point on the chart. Right click any of these to see the option—from a POI it is under More options. A grib must be loaded or the option does not respond. You can define up to 5 legs based on heading or true wind angle (TWA). Plus angles (+) are starboard side winds; negative angles(–) are port side winds. You can thus have up to 4 tacks or jibes in the DR track. The length of time spent on each leg is set in steps of "cranks." The default crank step is 5 min (Configuration//Boat/Crank duration).

Note you can do a grib reckoning with a forced wind, without having to load a grib.

Set up a
grib reckoning

Review loading gribs and viewing gribs, and also Polars

1. From the region of interest, prepare the grib you want to use: Close all gribs, load grib to be used in Slot 1, set start time with the toolbar clock—or you can force a wind of your choice without a grib.

2. Confirm that the crank step is 5 min (Configuration/Boat/crank duration), or set it to what you want. (If changed, remember to reset it when you carry out routing computations.)

3. Confirm you have the polar loaded you want to use. You can open the dashboard and view polar to see its name, but recall the special functionality of the dashboard polar. Once you know your starting location and time you can set the wind in that polar to see the TWA you  might want, but otherwise it is not providing information during the grib reckoning.

4. Check that the engine-on protocol is as you want it in menu Boat/Boat settings/Engine and Tacks/Gybes. For example, you might choose that if the sailing speed drops to 3 kts, you turn the engine on at a speed of 7 kts. If you sail at all times (as in a race), then set the sail speed and engine speed to 0. This window is also a place where you can account for loss of speed during a tack or jibe, but this function is not used in grib reckoning—the engine on function is in effect, but time penalties for tack and jibe are not implemented; they can be left unchecked. This is also the place where you force all engine on. See DR under power below.

5. Start the reckoning with a right click and decide if you want DR by Heading or TWA.  If you choose Heading (always True, regardless of variation setting or choices elsewhere) then you go straight in that direction, but your speed is determined by the TWA in effect at that time and place on that heading. Normally you would not choose a heading inside the red sectors of the polar, unless you were counting on the engine. For normal sailing, tacking or jibing, you would choose the optimum TWA for the TWS present. After one or a few cranks, you will see where you are going, and then change course (next leg) or go back (remove cranks).

Note when using TWA you cannot enter any number greater than 180.0, which is the TWA limit.

6. For tacking or jibing, you just stop adding cranks, click the next numbered leg at the top of the window, and change the sign (±) of the TWA, and add more cranks. Remember you can do this study from any place on the chart, you do not need to start from the boat location. In a race, you can check to see what a similar boat some distance from you, or headed away from you, might have in front of them at a different place on the race course. If you over stand a mark, you can backup and then tack earlier!

Don't forget you can set a mark at your destination and turn on the laylines (click on the mark) and then you will not overstand! They take the grib or forced current into account.

For the next leg you must change legs first at the top. If you change the input for TWA or Hdg without changing legs, it redoes the leg you are on at the new setting. Also be alert that changing legs can revert a Hdg choice to default TWA. When reaching you can set the TWA or just choose Hdg and let the helmsman sort out the wind angles!  Note in this function, Hdg is the same as CTW.

When done, you can Close or Reset the DR. If you Close, the settings will be stored and then applied to the next place you start a grib reckoning from. In other words, you would just be moving that DR track to another starting point. To start from scratch, just press Reset.

This reckoning is done on an evolving wind map, which updates the wind at the boat position at every crank, but we do not see the displayed winds change. Thus you can see a track lifted or headed as your proceed even though the wind on the screen is the same where the boat is now as it was where it started. What we are not seeing is the actual wind at that time has changed. If you care to update the map you can right click any DR point on the track and choose Set grib date, and it will move the displayed wind field to that grib time—but we must know how this works if we want to DR forward from that.

For example, if I start at 00z, using 5-minute cranks, and go 12 cranks on one tack and then 12 cranks on the other tack, the time at last DR position will be 02z, but I will still be looking at the wind field for 00z. If I update the grib (Set grib date) it will then show 02z grib time and display the corresponding winds. But now the DR function will think I have started at 02z so my next next crank adjusts all these times based on an 02z start. I still have the right track, but the time labels will be wrong.  (The grib reckoning function works so well and so fast that this is easy to experiment with to learn the ropes.)

It is interesting, for example, sailing downwind, to start off on a given TWA and run for an hour or so, and with that track in view, change the TWA to see how the track and end point moves for that same time underway.

If a track turns red, it means you have either hit an obstruction or land. With out a chart showing this might not be obvious. Turn on a chart and zoom in to see what you hit.

A nuance of ending a reckoning is this: when done and you then Reset, it erases what has been plotted (if selected to erase the line and POI) but it has not forgot that starting point. If you click somewhere else to try a different DR, it will start back at your original origin. So if you want to start from a new place, you Reset and then Close the grib reckoning, then the next one starts where you want it.

Likewise, if you Close without resetting, and then start a new DR from a new location, it will move the DR track you had to the new location.  These nuances in behavior have definite applications once you learn more ways to use this tool.

Store POIs

Store Reckoning

These two options in a grib reckoning (GR) window determine what is left after you cancel the GR. As you create the GR, the points made are stored in the Marks Manager, named with their ETAs. If you do not mark Store POIs, then when you close the GR, they are removed from the Manager. With Stored turned on they remain in the manager after you close the GR and there they can be used to created a pathway or route. Storing the Reckoning simply keeps the line on the chart when you close the GR, but if lines and points are both stored, they are not linked to each other in any way. To remove the stored reckoning line, just start a new GR and then cancel.
DR under power Still need grib, but to force all power on, go to menu Boat/Boat settings/Engine Tacks&Gybes and set Use engine if boat speed less than equal to, say, 80 kts and then enter the engine speed you want. This will force all under power DR.  Remember to undo this when done!
3.4 Routes 

Recall that in qtVlm terms, a "pathway" is a sequence of waypoints defining a path or desired track between a departure and destination, with no means of propulsion implied—other apps call this a "route." The concept of route in qtVlm implies we have assigned a specific means of proportion to a pathway and thus each waypoint along the route has an ETA. Routes can be for sail or power vessels. The default is sail, with the engine-on criteria set in menu Boat/BoatSettings/Engine, tacks-gybes. It is important to check this setting to be sure it is where you want it—i.e., if sail speed is less than 3 kts, turn the engine on at speed 6 kts, etc.

If you want all engine-on routes, set the minimum sailing speed to say 50 kts, and choose the engine speed you want. This will force engine on at all times as we never reach sail speeds of 50 kts.

Even if we plan an all engine route, a wind forecast (grib) must be loaded for the region and duration of the planned route (see Load a grib), and a polar diagram must be selected. The default polar installed is for a classic 40 ft sailboat. When the specific wind forecast is not crucial, the simple and quick Partial VLM grib will do. Then you can hide the wind barbs (globe icon) if desired.

Also, even if you wish to compute sailing routes using forced winds of your choice, you must still first load a grib, and then force the wind, which will override what the grib forecasted. Just load a Partial VLM grib, then force the wind you want.

After you create a route, the program computes the ETA at that waypoint based on the wind and polar in effect at that time and place—or the engine speed if the sailing speed is below your selected limit. When computing this, it is not aware of what the wind might be later in the forecast in the vicinity of your destination. Thus routes might be best for shorter runs or for ones where you do not anticipate much change in the wind—which you do not have to guess, because we have the forecast loaded and can step through it.  For longer runs or in changing winds, a routing computation using isochrones then converted to a route (Method 3 below) might be best solution, because that solution does look ahead and assure you end up in the best wind.

Keeping in mind these limits, routes are very fast to make, and once made can show instantly how they change if you change starting time, or place, or destination—or add current or waves, or if you change the forecast by switching to another model forecast.

Starting point

From boat. This choice must be used if you intend to activate the route, and usually the logical choice when actually sailing or running a simulation. If you are not actually in the boat with the GPS on, then be sure you have the boat located where you want it to be.

From 1st mark. Best choice when not underway or simulating. Use this one for route planning, studying options, and working course exercises.

Start time

Start time must be within the span of the wind forecast (grib) loaded

Last Position update date/time. This is the choice typically used when actually sailing, or maybe in some simulation exercises.

From Grib date. This one could be used underway, or it could be used to see how the route changes with starting time or date. With a route computed, and this choice set, the route will change dynamically as you change starting time with the slider or time step buttons.

Fixed date & time. This is the best choice if you want to see a boat or boats move along one or several different routes as you advance the grib time from the start time. Planning a specific start time, this is the best as you can choose to save this time.

Navigation mode

-- Great Circle Means the boat will follow the great circle track between points, using whatever speed the polar presents for the TWS and TWA (angle between GC heading and wind direction) it confronts as it proceeds and the forecast advances. This is usually not an optimum route, as it will not likely have the best TWA, but it can give a benchmark of sorts. A similar benchmark might be to just divide the distance by an estimated SMG.

-- BVMG Stands for "best velocity made good," which in qtVlm means best VMC (velocity made course.) This means the program finds the heading that maximizes your boat speed in the direction of the mark. It will make this choice at every crank, unless we set a minimum number of cranks between tack or jibe (see boat factors). This is a mode we might often want to be in, but it is not looking ahead to what the wind will be later on. Routes are always looking at present wind. We need to move on to routings to look ahead to what wind we find ahead.

-- VBVMG stands for "very best velocity made good," which in qtVlm means sail the great circle route as described above, but if the resulting TWA is outside of the favored range for that TWS (not in the green part of the qtVlm polar presentation) then the boat will tack or jibe to the destination, again honoring our tack and gybe limits set in boat factors.

-- Automatic means the program looks at all three options and chooses the one with the shortest route time. This is generally the best setting. Under power it defaults to great circle.

Four ways

to create

a route

Method 1. Create waypoints (POI) as you build the route.
1a. Menu Routes/Create a route
1b. Give it a unique name, confirm right polar selected, choose Start point, Start time, and Nav mode (as explained above)
1c. Options. Turn off: Freeze route, Remove POIs, Hide POIs, and Hide route. Turn on Draw wind at POIs, POIs by sequence number, and Detect collisions (set distance at 0.1 nmi), Turn on Auto zoom on simplification.
1d. Then click Append POIs and start clicking the screen from your intended start to your destination in as many steps as you like. You should see the ETA of each appear in the mark name, with a line between them. You can use the navigation arrows at the top center of the screen to access off-screen areas. If you need to adjust a POI potion after setting it, just click its label wait till it turns blue and move it, then carry on with adding POIs. When done, press the sign at the top of the screen that says Stop append POIs, or press ESC key.
1e. You have made the route, now we can look at the results. See route log section below.

Method 2. Use existing waypoints (POI) to create a route.
For setting up a route from a given set of waypoints there is another approach. This is useful for those planning a race that you know will use several known marks, but you do not know which ones till race day. The full set of marks can be stored in the Marks archives and loaded for setting up the route. This method is also used when you obtain a set of waypoints for a complex route from an outside source... or you may simply want to layout the marks more carefully before creating the route.

2a. Load the marks you want to use. Sets of marks can be imported or created individually and stored in the Marks Archives.
2b. Go over the marks you want to use and name them sequentially with a number and a description, such as 01 Jones Dock, 02 Mission Rk, 03 Approach to Alkaid, etc. These can also preceded by the same letters, such as ABC 01 Jones Dock, ABC 02 Mission Rk, ABC 03 Approach to Alkaid, etc, with or without dashes, i.e., ABC 01 or ABC-01.
2c. Follow the steps above 1a to 1c to create and define your route (let's call it "myroute"), but skip 1d, and just exit by pressing the OK button. This stores your route, but so far it does not have any waypoints.
2d. Now starting with your first mark, right click it and choose route/myroute; then do the same sequentially to all of the marks you want in the route. Just stop adding them when you are done.
2e. You have made the route, now we can look at the results. See route log section below.

Method 3. Use an existing pathway to create a route
3a. Create a pathway you want to convert to a route. Be sure the waypoints are numbered sequentially, see step 2b in Method 2 above. Pathways can also be imported from ones you made earlier and exported.
3b. The do menu Pathways/Edit pathway and at the bottom of the window there is an option to Export GPX. Do that and note where you are storing it. (Note, do not do menu Pathways/Export. That will save it as a qpar file, which can be used to import the pathway again but we want to do something different.)
3c. Now do menu Routes/Import a route in VB-VMG mode and select the pathway GPX file you just saved. This will replace the pathway you had with a route of the same name.
3d. Now edit that route and turn off Freeze route and turn off Hide Intermediate POIs.
3e. You have made the route, now we can look at the results. See route log section below.

Method 4. Compute a routing and convert it to a route.
4a. After you complete a routing the natural last step to that process is to convert it to a route. See routing.
4b. For shorter routes, the routing options must be adjusted as explained in that section.
4c. Once you have made a route this way, you can look at the results. See route log section below.

Route notes

If the waypoints do not connect with a line as you place them, see Troubleshooting below. If a connecting line turns red while making the route it means that leg is crossing a hazard, even though it is not apparent on the present display. Turn on a vector chart of the area in Detailed Mode to see the issue. See Alarms.

Times on each waypoint along a route are based on the start time and the polar speed or engine speed set earlier. Grib time is the one shown on the top left of the screen, you can set it with the clock icon and then fine tune with the time buttons in the tool bar.... or for a specific time, go back to Edit route and choose a specific time for the starting time. You can check anticipated progress and conditions any place along the route with with a tooltip on any place on the route.

When you make the waypoint selections for an engine-on route, you are choosing the route you would like to make good when going by engine at the speed you set. If there is current present, the actual heading you must steer to make good this route will not be the "COGs" of the route legs. You will have to point into the current on each leg. qtVlm will inform you as noted below of what heading to steer in each case. You can add current to a route, as outlined below, to practice with this.

Route Logbook

This is where we check to see the properties of each leg of our route. Do edit route (menu Route or highlight the route and right click it) and then choose second tab Route Logbook.

"Boat factors"

Crank size

Minimum time between
tacks or gybes

For short routes we need to reduce the crank size to 1 minute, else computing every 5 min (the default crank size) we might skip over or not quite get to a mark of the route. Set the crank size at Configuration/Boat/Crank duration. With a small crank size, you may find routes with unrealistic tack or gybe intervals... this might even be seen with a 5-min crank.

Control the tack and jibe intervals at the same place you specify how much time you lose when doing either maneuver, Boat/Boat Settings/Engine and Tacks-Gybes. This setting is normally used to reduce boat speed by, for example, 90% for a period of 1 crank, so if we had a crank size of 5 min, and we were sailing at polar speed of 7 kts, for 5 min the speed would drop to 0.9x7=6.3 kts. But if we just want to show a route with longer tack intervals with a crank size of 1 min, we can set the correction to 100% and then choose 20 cranks. This way the boat will not tack (or gybe) at intervals smaller than 20 minutes.... but we are not adding any penalties.

Laylines Laylines to a mark for any wind or time can be turned on from right click on the mark. See Laylines
Tooltip on a route

After a route is computed and displayed on the screen, you can put the cursor anywhere along the route to read all crucial info about boat and wind at that point along with time to next mark and time to the end of the route. This read out does not depend on the grib time, but only on the location along the route. If there is current present, the tooltip will report to you the course through the water (CTW) you must steer to make good this leg.

Dot on route
All routes have a starting time and either an engine speed set in Boat Settings or Simulator, or a polar that determines speed along the route. As you advance the grib time, a dot will mark where the boat is relative to the start time. Cursor on the dot shows wind and boat performance. For the animation to work, in Route/Edit route we need it not frozen and the start time set right, and we need the waypoints in the order specified (alphabetical or by sequence). Multiple imported or saved routes can be animated in this way simultaneously if they overlap in time and grib data.

Route Logbook




Pathway plan

Once a route has been made, with start time and engine speed, the Route Logbook tab in the Route Settings screen (Edit route) shows the "route plan" for the route. The parameters shown can be selected with the gear icon on the top left—click the gear, then click on or off the ones you want, then click the gear again to set your choices.

There are two ways to view of the data set on the top right, by time interval, such as every 30 min or every hour, or by degree of heading change along the route. The latter would typically then give one line of data at each waypoint, assuming the next leg is at a heading change greater than the limit set here. This is a more subtle choice when under sail, where wind and heading can change along a route, but even under power, if we have current on the route (see below) the heading can change when the current changes.

Parameters that can be displayed include speed through the water, course though the water, COG, SOG, current speed, current direction, Lat-Lon at the boat, name of next waypoint, distance and course to next way, Lat-Lon of next waypoint, and more.

This route plan is an important document for any voyage and should be printed out as a back-up to all instrument failures. It can be exported as a CSV file. For most applications we would not want the "raw data" as that provides too much intermediate values. Even for a route intended to be sailed, it is valuable to choose an anticipated average speed made good, and make such a plan as if under power at that speed and print it out. This is also a helpful guide to laying out the route on a printed chart.

If you want your destination to show up in the logbook, then the route must begin from the boat, not first mark. This might change, but that is the way it is now.

Histograms tab The histograms are plots of values vs time along the route for any of the related parameters including how wind and current changes along the route. Used more often under sail than power, but applications are many on any vessel. The instruments must have been turned on during the route to see a histogram.
Statistics tab This tab provides a summary of the full route and individual legs, showing lengths, durations, average speeds, average winds, and so on.
Effect of current on a route

You can add current to the route computation two ways. One for ocean and coastal waters, you can load a grib of the ocean current forecasts from, for example, the RTOFS model. To do this you would use grib slot 1for wind and grib slot 2 for current. 

The other way to add a fixed current to the route is through the grib configuration setting, which you can get to several ways:  menu Grib/Grib configuration/Corrections or get there from the windsock icon in the toolbar or from keys cmd+G.  Then click Force Currents and enter the current speed (CS) and current direction (CD). This will then be applied over the full route, independent of location or time.

With a current applied by either method, the affects of the current on the route will show up everywhere route data appears: tooltip, logbook, and statistics.  In the Histogram display you can see a plot of the current speed or current direction over the extent of the route.

Alarms When laying out a route, the leg will turn red when it crosses a hazard, but it only knows if hazards are there by the setting for coastlines in Configuration/Chart top line. If no vector charts are loaded then turn off that option and it will use the base map, but this will be land only. Best to load an ENC, then set that option to ENCs, and we get alarms at rocks and land, even if we are looking at an RNC or no chart at all.
Lock or pause changes to waypoints

When working with routes, it is safest to pause the easy POI motion so they are less likely to be moved by accident. Use menu Configuration/General and near the bottom turn off Allow POIs to be moved immediately. Then you have to click one, wait till it turns blue, then move it.  There is also the option in menu Route/Edit route/ route-name  then Freeze the route,  which will lock all waypoints, POI or otherwise.

Paste a route from OpenCPN A route created and displayed in OpenCPN can be right clicked, then choose Copy as KML and select Extended Waypoint data for qtVlm, then anywhere on the qtVlm screen right click and paste route. This route will appear here then, more or less as made here. See our note on Sharing Routes Between OpenCPN and qtVlm.
Selecting a route To select a route with the cursor that is displayed on the screen, the route must go bold, else you are not selecting the route but the chart below it.
Save Routes After making a route that may have taken some work, you can save it with cmd+S or ctrl+S. This step saves marks, routes, and barriers. Also access from menu Marks/Save POI and routes, which is where you would reload it if saved this way.
Route timing

(1) When you start from scratch, even with an older grib installed, grib date starts with the present time of the computer. Thus when you choose start time From Grib Date, it will default to the present time... since that is what will be showing in the Grib time on the top left of the screen, just below grib run time. That time will then be permanent on the route POIs until you change the Grib time with the step timer in the toolbar or the clock dropdown, or the slide bar if turned on.

(2) You can view progress along a route under power with a tool tip over the route location of interest. It will use the speed set and the start time set.


(1) If route waypoints (WP) get placed, but no connecting lines show, and WP names are "Can't get here with this grib," it likely means you either do not have a grib loaded, or the Route/Edit route set up has a route starting time not covered by the grib.  You need a grib even for power-driven routes. To add a quick one, do shift-drag over the region, then right click and choose VLM Partial Grib. Then set the time with the toolbar clock to that of the first file. If you do not want to see the wind, then shut off the display with the yellow-green globe icon in the toolbar.

(2) Speed readouts wrong. See Comparison note below.

Export and import routes Export a route from menu Routes/Export route, which gives a chance to name the GPX file, which is in standard format to be imported to any device or program . Likewise, menu Routes/Import route/GC mode will load a GPX route. It will show up in the locked mode (frozen), do Routes/Edit to unfreeze it. When you export you will be asked "Just POIs" or "Details." The former is Lat, Lon, and time at each POI only; the Details tells you Lat, Lon, and time at each crank point (meaning at each place where a computation was made). The default crank step is every 5 min.
Comparison and analysis When looking at the valuable function menu Route/Route comparator or just looking at the tooltip outputs or the logbooks, be sure there is no unusual setting on the engine on speeds set at menu Boat/Boat settings/Engine and tacks-gybes. If you had set that, for example, to force the engine on at all times, then that is what you will see on the route outputs. The boats will move along the route at the right pace as you advance the time, but the speed read outs will be wrong.
"Route Plan"

There is a thorough route summary (logbook) from menu Routes/ Edit Route... /Logbook. See Route Logbook above. See also Pathway Plan above, which is a summary that can be printed as a back up to electronics failure.

3.5 Routing with isochrones 
  WORK IN PROGRESS: This is one of the main sections of the program and we are still working on this.
Routing settings

Base settings with no corrections. Each of these settings can affect a routing. See video Example.
We first do a routing between two points away from land, more than 200 nmi apart.

NOTE: in all windows we open, be sure you are looking at the full window.
Pull the bottom right corner to be sure all options are in view.


• Download qtVlm Routing Practice.pdf, which has detailed instructions on loading the grib file we will use.
• Load the grib as outlined along with the start and finish points, labeled "CSR Start" and "CSR Finish" (CSR = Cheat Sheet Routing!)
• Note the start time of that forecast. We will call this "grib start time." Sample value to use is in the Practice PDF above. (This is not the first forecast in the file.)
• Turn on Grib time slider to see that you have data points for several days. It shows one dot for each forecast, although qtVlm interpolated between them as well.
• Use right click Query grib data near the planned routing area to see you have wind values.
• With the clock icon, set the grib time to the selected Grib start time.

Menu Boat/Boat settings/...



• Check that the polar you want is loaded (top dropdown).
• Up, down, night efficiency, all = 100%.
• Best angles upwind, downwind = auto.
• Click Waves and gusts tab.

Waves and gusts

• Wave polar = None
• Apply steepness correction = Off (unchecked, yellow).
• Crossed seas: leave default (1.0, 45°, 100%).
• Gusts: leave default (30%, 100%).
• Click Engine and tacks Tab.

Engine and tacks

• Use engine if S=0, Engine speed = 0
• Tacks and Gybes penalties = Off (unchecked, yellow).
• Click OK.

Menu Configuration/Boat

• Crank duration = 5 min
• Click OK.
Menu Configuration/
Gribs and Harmonics

• Turn on: Zoom on grib after download and Show Saildocs options
• Turn off everything else in that section. (Later we may want to extend currents.)
• Click OK
Menu Gribs/
Grib Configuration/...
• Turn on All slots (we will change this later).
• Turn on Display grib time slider.
• Turn on Grib over charts, opacity half scale.
• Background = Wind map. Main arrow slot 1 = black. (This can all be changed to preference.)
• Click Corrections Tab.


• Everything off.
• Click Close.

Create a Routing/...

General settings

• Name the routing, such as "CSR Routing," or as desired.
• On top right confirm polar or select desired one.
• In Start and Arrival points, turn off both Routing from Boat and Use a Pathway. In the drop down below those, choose top one to be the saved mark CSR Start, and the bottom one CSR Finish.
• Set Routing start date and time = grib start time (See Routing Practice, can be copied and pasted).
• Turn on Keep starting date (makes repeated practice runs easier.)
• Turn on Automatic parameters; move slider full right to Best accuracy. This will get best results but takes longer. Move slider to half or quarter scale half scale for faster solutions.
• Turn on Convert to Route using... (This is the normal and default choice. Later we can leave this off and compute Reversed isochrones to study dependability of the solution. Can't do both in one run.)
• Click Options tab.


• Leave 24h isochrone defaults: 20m, 60m, 3°, 180° (If you choose Automatic in the General settings, you cannot change these first options.)
• Turn on: Use VB-VMG and Avoid barriers and coasts and Do not route outside the screen and Show isochrones.
• Turn off: Max distance from GC and Color TWS between isos and Multi routing (which means settings in that box do not matter).
• Click Advanced Settings tab.

Advanced Settings

• Leave all at default.
Ready to go! • Press OK and you should see the isochrone computation start.
  • Then when Completion window shows up, press OK.

• On the Conversion window choose:
-- From Routing Start
-- Simplify
-- Optimum
-- Press OK (The process takes a few seconds.)
• On the Simplification result window, choose Optimize.
• At the end of that report, press OK and we have our optimum route.

Menu Routes/
Edit route

• To view properties, which we discuss in the Routing Practice PDF.
• Later we will add current and waves, and other refinements.

Automatic parameters function

-- For most routings we turn this on and set the slider about about half scale. With this on, several Options and Advanced settings cannot be changed.

-- For short routes, shut this off so we can access Options and Advanced settings.

Error msg "Start point (or Destination point) is not within minimal coast distance." This means you have set a limit on how close the route can get to land or a barrier at menu Routings/Create a routing/Options/Avoid barriers and coasts  and then set the start or finish point closer to land than that limit. Move the offending mark or the limit to fix this.
Short routes

-- set crank step to 1 min
-- remove tack and gybe penalties in boat settings
-- with auto parameters off, set isochrone step to 5 min

Limit routings with barrier or shallow water contour choice. A computed routing will not cross a barrier. Thus you can use barriers to force a way around an island or to block off certain passes. This can be done with lines or closed barriers. Routings are also limited by land, or more specifically by the shallow water contour displayed on the chart. See related discussion under shallow water contours. Also note that shoreline is assigned to the S57/S63 charts in the chart set up page, else it uses the coastline of the base map, which is not nearly as accurate. Recall you can always check for grounding as it will show a red obstacle alert when using the ruler tool to cross it.
Tips -- Routings can be initiated from a right click anywhere on the chart or from menu Routing/Create a routing.
-- When using a pathway to define the start and ending points (as opposed to from boat to somewhere) make that pathway from start point to finish point first, and tell it to start from first point, not from boat. Then hide that pathway. We have plenty enough lines on the screen in this process.

Ocean or inland currents in grib format will automatically be included in the isochrone computations if loaded in one of the slots or if included in a combined grib file, so long as there is an overlap in time and space for the data. In menu Configuration/Gribs and harmonics/Automatically extend current grib last date this choice will freeze the current data to be the same if it does not extend. Often the currents forecast is shorter than the wind forecasts.

* * * If you extend the currents, the slider will then go the length of the longest grib. If currents are the only grib you have loaded and you extend the currents, the slider will extend one year, which makes it unusable. Thus with only currents, shut off the extend currents option.

3.6 Barriers 
What they are

These are line segments, open polygons, or closed polygons that can be used to restrict passage or slow it down. A computed optimum routing cannot cross them, but a route or pathway will cross a barrier. Barriers can also be used to trigger alarms in real navigation or in simulation. The alarm goes off when the COG predictor line crosses the barrier. These are commonly used to force a routing computation into a specific direction, or to block off a pass. They can be used in routine navigation to outline a hazardous area on the chart you wish to be warned about. They can also be used as a way to draw a quick line on the chart... keeping in mind they also have navigational significance. Barriers behave much as "Notes" do in Expedition.

Create a barrier

Use menu Barriers or the toolbar icon (alert sign with a fence), or right click anywhere on the chart and choose New barrier. The latter will start the barrier where you clicked; the toolbar choice starts where you then first click. Then just keep clicking to draw the barrier. End that barrier with the Escape key or press the End barrier input button at the top of the screen.

To create a closed barrier, draw part of it, then end the input, then right click the line (it will highlight) and choose Closed barrier.

Barriers, open or closed, one or many, are referred to as a "Barrier set." You can name or color the full set with a right click on any one and then Edit. This will apply to all of the them. Note that to interact with a closed bearing, you must right click the bearing line, not the cross-hatched inside.

When creating a no-go zone for routing, do not hesitate to enter a few extra points, which then allows for editing as might be needed without having to start a new one. There is no insert point option.

Slow zone. With the right click, you have the option to define a closed barrier region as a "slow zone," meaning for whatever reason you choose, the routing can go across this area, but will be slowed by the percentage you enter. This will always be a reduced speed, not ever enhanced speed. Original motivation was provide a routing slow down for boats in a region of Sargasso weed.

Show, hide, delete a barrier Once created, you can show or hide the full barrier set from the menu View/Show-hide/Show barriers. To delete a barrier, right click the border and choose Delete.
Save barriers After making a set of barriers that may have taken some work, you can back then up with cmd+S or ctrl+S. This step saves marks, routes, and barriers. Also access from menu Marks/Save POI and routes (does not say barriers, but does include them).
Save or export Barriers are saved automatically, but you can backup one by exporting it at menu Barriers/Export. This saves a barrier_name.qbar file that can be then reloaded as needed. or
3.7 AIS

qtVlm has an excellent presentation of AIS targets that can be used with live NMEA data, simulator, or file replay. The main set up pages are at menu Configuration/AIS, which has three tabs: 1. Options, 2. CPA/TCPA, and 3. Display.

Toolbar AIS icon turns AIS target display on and off.

Show a list of all AIS targets (when activated) using menu View/AIS targets list at the bottom, which is a valuable resource.

1. Options

Controls what targets are seen on your screen.

Ignore if farther than... Used to hide targets farther than this limit. Internet only targets only extend to 50 nmi from your boat, so only lower values will make a change. Live targets are rarely more than 25 miles or so from a small boat. You can set large values or shut this off to see global vessels running qtVlm with live AIS who have chosen to share their position. They will show up as pink targets.

Names Means just that, show the vessel name next to its icon. This must wait till the target turns green meaning it has the static data, which is broadcast only every 6 min.

Show only Friends You can right click any AIS target and at the bottom of the options define it as a "Friend." This puts that target into the Friends category, and then you can choose to just look at Friends. Keep in mind when that is turned on you may miss crucial traffic.

Track Means turn on the track of all vessels. There is rarely any reason to shut this off as the tracks are crucial to interpret the motion of the vessel, which might contribute to your evaluation of risk of collision, although there are other more timely displays for this. Shut this off to hide the tracks, and if you turn it back on the tracks will come back. To get rid of all tracks, shut the AIS off and and back on again... but you will have to wait for the static and voyage data.

Target is lost after... AIS signals are sent on a prescribed time schedule, at intervals varying from every 2 seconds to every 6 minutes. But targets can sail out of range of your receiver, or they may change their AIS status, or turn it off. This control lets you set how long you wait to see if a target is really lost or not. When this set time as passed since the last received signal from a specific target, a black line is drawn across the icon, which lets you know it is missing signals. Then after the second period has passed with no signals, the icon is removed from the screen.

Reckoning This is the COG predictor time interval that works like the one we set independently for our own vessel. The end of the predictor line shows where the vessel will be at the that time interval from now. A small dot marks that location. We recommend having this time for AIS targets be the same as you have for your own vessel. This is a dynamic parameter that can be changed to meet circumstances. At 6 min, the length of the line is one tenth of the vessel's SOG. Multiples of 6 min is therefore popular for this. At 12 min, the predictor length is twice the speed; at 3 min it is half the speed.

No moored or speeds less than... This is usually a useful option to turn on to limit in appropriate CPA information and reduce clutter on the screen. Likewise limiting vessels of interest to over 0.2 kts can also be of interest. But sometimes with a lot of slow or anchored traffic in the region you might want to shut this off so you can see every vessel and then use CPA settings to clean up the screen.

Real size Every vessel using AIS should specify its dimensions relative to its GPS location so they can be broadcasted to other vessels within their AIS signals. See Vessel icon section 2.1 on Boat Settings. This is done for own boat at menu Boat/Boat settings/Dimensions. Turning this on and zooming way in so they can be seen (watch the chart scale display), you will then see the actual dimensions of the target. If you have set your dimensions, your icon will also be shown the right scale. This is a very informative tool and can be used for close in interactions with other vessels or for docking practice. Recall qtVlm will let you go backwards!

Use VDO messages This can be left off. It is only for live navigation from a boat that has an AIS transponder (all of which include their own GPS) but for some reason the boat either does not have any other GPS or does not want to use their main GPS. This option lets them use their AIS GPS to keep track of their position on the screen.

AIS via internet Recall we can see AIS vessels when doing a simulation by just turning on the AIS icon in the toolbar. This option lets you view internet AIS without being in simulation mode. These internet AIS targets will show up with a red dot, because you can also turn this on when running a live AIS receiver, and then you can distinguish internet targets from live targets. See section below on internet vs live AIS.


Controls the display of closest point of approach (CPA) data depending on how close the CPA is and how long before it occurs (TCPA) These are dynamic settings that could be changed as conditions change.

Calculate if target distance is less than.. This is where you limit displayed interactions with vessels that are too far off to matter at the moment. Note the interplay with the next control. You can keep this high for early alerts, but only if the anticipated eventual CPA is less than set below.

Show if CPA is less than... On contested inland waters this could be well less than a mile, but in the ocean this would likely be set to several miles or more. We will also want to take into account the speeds of the vessels involved. For fast traffic, this has to be kept larger.

And if time to CPA is less than... This is tied to above choice. Again, this is a balancing task, depending on conditions.

Ignore CPA for moored targets... Usually turned on to avoid screen clutter. This does not hide the targets, which are marked by an anchor ball dot, it just prevents displaying CPA data to them. Note we have the option above to not show them, but it is likely best to show then just not compute them.

Ignore if targets are across land... This would generally be turned on to minimize clutter, but it could be the above settings does that for you and you could leave it off. We definitely want to shut this off (so we can see across land) as we approach entrances or crossing waterways where approaching traffic could be hidden by the land. This is indeed one of the key benefits of AIS over radar. Again, a balancing act to choose best settings for conditions at hand.

Use real size for computing CPA if less than... In practice we always want the real size of vessels to enter into the CPA, but above 0.5 nmi or so (1000 yds) this won't change the numbers. We can just leave this at the default 1 nmi. When looking at very close encounters, such as docking or tug meets ship practice, then we need to really know where the GPS is located on the vessels, and when zoomed way in on real size vessels you will see that qtVlm shows the GPS location. The CPA computed is GPS to GPS.

3. Display

Select type of AIS to see.

General... Class A, Class B, and ATONS are the main targets we want on. ATONs are special aids to navigation that have been fitted with an AIS transmitter. Some of these are on real objects (buoys or beacons or bridge pillars) and others are virtual, often as a virtual buoy in a waterway, but you can treat it as if it were indeed a real marker on the waterway.

AIS symbol size... You might find mid-scale or a bit bigger best for working with traffic. This also makes it easier to see your own AIS symbol on top of your boat icon.

Own boat and AIS target size Recommend setting AIS target size to just over half the range, which is larger that the default: menu Configuration/AIS/Display. Also, even tough we might use larger own boat vessel icon size for other work, for AIS work you might find it best to have own boat size same as AIS size, in which case your own AIS symbol can be seen and you have a better view of the relative COG projectors lengths. About quarter scale at menu Boat/Boat settings/Icon size.
Reckoning Usually most productive to have own ship reckoning time be the same as the AIS times. Recall that at 6 min, the length of the predictor is one tenth of the vessel speed.
Global AIS with simulation A powerful training feature of qtVlm is that whenever you are running a simulation, you can turn on a display of local, live AIS traffic and interact with them as if you were there in that traffic. You have all the AIS controls outlined here that can be practiced. This is turned on with the AIS icon in the toolbar. Needless to say, despite the realism you experience in this exercise, they do not see you and there is no risk to real navigation.
Internet vs live AIS

During simulation with AIS turned on we are always looking at AIS via the internet. On our own boat underway (or at a land station on the coast) you may have access to live AIS from your own antenna and AIS receiver. You see the live data by telling qtVlm the source of the NMEA signals you are receiving. These could come in via a single network connection that brings in all of your NMEA data at one place (such as an N2k backbone string of many instruments transmitting the data to qtVlm via a wifi or USB gateway, or you might have separate local USB ports for various data types.

When running live navigation with your own NMEA stream you would not typically use the internet AIS, you would use your own live AIS which is best, because it updates in a timely fashion as specified by known rules. Internet AIS, on the other hand, is much delayed, often by a minute or more. A fast vessel seen approaching you on internet AIS could be well past you at that same time.

But if you do not have a real AIS receiver, and are aware of this timing caution, then internet AIS can alert you to approaching traffic. To turn that on when you are using live NMEA for position and other data, use menu Configuration/AIS/Options/ and turn on AIS via internet. The other settings in that section can be left off. Then close and then press Start NMEA on the microboard. AIS icon in the toolbar must be turned on. When you view AIS via internet this way the AIS targets you see will be marked by a red dot.

You can also turn this on at any time in this manner, with or without a live NMEA input, and see these targets. You are not running the simulator, so if you are not doing live navigation, you cannot drive your boat, but you will see all internet AIS within 50 nmi of the boat position.

If you turn this on with a live AIS running at the same time, qtVlm will ignore AIS targets from the internet if there is a live version of it, which leaves you with only red dots on targets that show up on the internet source but not the live source. The red dots would typically be seen near the limits of the range of your live AIS receiver—internet AIS data comes from 50 miles out from your boat, whereas real AIS broadcasts (at least from Class B) from more than 5 or 10 miles is rare.

AIS icon colors

— yellow = no static or voyage data yet
— green = full static and voyage data
— red = CPA risk, within user assigned limits
— gray = lost target, i.e., no signal for the preset time interval
— olive green = friend
— blue = simulated vessel
— pink = real vessel running qtVlm, using internet AIS, and sharing their AIS data with qtVlm users.

AIS icon shapes

— square stern = class A
— v-shape stern = class B
— line across the beam means target lost.
— black dot, reported as moored (anchor day shape is a single ball). When moving at 12 kt clearly not correct!
— point to point cones = reported as engaged in fishing. Often not correct. Recall, a "fishing vessel" is not a "vessel engaged in fishing"!

In European waters (especially rivers)
— a small ball on the bow means running EU Inland AIS. They will include a EURO VIM number in Details.
— blue on the starboard half of the icon means running with a Blue flag (blue sign), meaning expects passing on its starboard side. For some reason it has to drive along the wrong side of the river.

Practice with others See this video on simultaneous simulation.
3.8 Replay NMEA Stream 

Use Configuration/NMEA
—Choose file
—Replay speed
—Number of lines (count lines between successive RMC or GGA sentences)
—Take current date and time from NMEA (NMEA time will show on microboard /position)
Note: Time is extracted from either GGA, GGL, or RMC sentences.
—Turn on replay slider controls at Configuration/NMEA connections. Top one is speed of replay; bottom is location within the file. Both can be changed while running.

File structure

— Easiest form is use NMEA sentence RMA.
— Do not need satellite sentences (i.e. GGA, GGL, etc), but GGA or GGL will signal valid GPS.
— Check sum must be right.
— Can have leading characters on each line, as long as NMEA consistently starts $ or !

Notes —Start it running from microboard (Start NMEA). Must have interval at least 1 second.
—Click COG/SOG on bow to center the vessel... or opt+B.
—Do not need Grib for fake NMEA stream.
4.1 Loading Gribs
Make a grib folder

For a background on grib files see Starpath Grib School.

We recommend you make a folder on your computer dedicated to storing your grib files, such as Documents/MyqtVlm data/MyGribs. To direct all grib downloads to that folder use menu Configuration/Gribs and harmonics and then Browse for that folder with the button to the right of Ask for destination... Leave that option off, and then all gribs will go to that folder. Such a folder allows for easy clean up as needed or a way to find a backup for a file deleted by mistake. The folder can also be duplicated as a way to archive the record of your voyage or race. Then we can add, i.e., /MyHarmonics or /MyASCAT, etc

Zoom to grib
In the next line down, consider leaving off the option to delete old gribs. With a custom folder this is easy to do, and you might want them later. Turn on zoom to grib, that is usually what is wanted, and definitely turn on show Saildocs options, because these are often changed.
Load one or more grib files

You can load up to 3 grib files at a time and then show any one or any combination of them. They are loaded individually into Grib slots, starting at the menu Grib/Grib slot 1 or Grib/Grib slot 2 or Grib/Grib slot 3.

There is a quick way to load a GFS grib into slot 1, shown below. Also later we show how you can use qtVlm to combine gribs (see Merge gribs below), which has several applications. Recall that GFS provides wind and waves in a single grib file.

Slot usage

If a grib file is loaded without first specifying a slot number, then it defaults to slot 1, overwriting what is there and removing other loaded gribs. The blue Open a grib icon in the toolbar loads into slot 1, overwriting what might be there.

Under specific slots there is no Saildocs option, because that method brings the file to your MyGribs folder, which we load from menu Gribs/Grib slot x/Open, as noted below.

When you want two or more gribs active at the same time their green arrows must show. Just having then loaded in the slots is not enough. Thus with GFS in 1 and RTOFS in 2, you must see both 1st and 2nd arrow to have them both active.  See also Merge gribs below.

Quick grib load Shift drag to set the region, then right click and choose VLM partial grib. This will load GFS wind only, every 3 hr for 5 days, at 0.5° resolution for an expanded region that includes what you selected. The region loaded will always be somewhat larger than what you selected.
If grib does not show

— A grib will typically not show until you select the time you want with the clock in the toolbar. Click the clock and choose top time for the first in the sequence.

— Check that the gribs are not turned off with the world map icon in the toolbar (Off will have a red line across it).

— If you had at some point chosen the option to just show the wind barbs at the true grid points, then this could spread out the barbs so much that you do not know they are there. Zoom out to check that. This setting is in menu Grib/Grib configuration (windsock icon in toolbar or cmd+G called Wind on grid points.

Choose a grib source

We have three choices: (1) load a grib file that is stored on our hard drive (cloud, or portable drive), or (2) choose one of several sources to request the file from, or, more rarely, (3) access a custom source we have defined, which is a topic of its own.

(1) To load a saved file, use menu Grib/Grib Slot 1,2, or 3/Open then navigate to the file, highlight it, and choose open. These can have any grib extension, and some compressed versions (gz, bz). Once loaded you will have to set the time to match the file in order to see the data.

(2) There are several options, accessible from menu Grib/Grib Slot 1, 2, and 3...

— Use the quick grib described above: Download partial VLM grib

Grib VLM is similar to the quick grib (5 days, GFS, wind only, every 3h), but it downloads the entire globe (a 33MB file) so it is not efficient underway. It does offer the option of taking earlier model runs, which can be useful for comparing with archived measurements or ASCAT wind data. To get an earlier model run from Saildocs, tack this on the end of the request |file=yyyymmddhh which can be used to get past runs up to 2 or 3 weeks old.

— Choose options from Grib ZyGrib or Grib XyGrib. Either of these download directly into qtVlm. As opposed to the previous two options, these allow for other parameters beside wind. XyGrib offers a couple other valuable models (the NAM it has is 12-km, not technically the 3-km NAM CONUS listed). There is nothing special to be obtained from the ZyGrib source.

— The option called Grib Great Circle is a link to a commercial provider that requires an account number.

Get Saildocs data One of the best sources of data takes a two step process: first use shift-drag to outline the area of interest, then right click and choose Grib Saildocs. This opens a window for you to choose from several models, with several parameters. Select those and press Send email. This will create the proper Saildocs request and put it into your default mail program. Send this and then shortly receive the file by return mail. Save to your MyGribs folder, and then use the choice (1) above to load it.
Custom grib download Find this option at the bottom of the menu Grib/Grib slot x/Custom download. This is your access to any custom source of grib data that you entered at menu Configuration/ Gribs and harmonics/Custom URLs. This URL would typically be to an online directory of files from which we then choose the file we want. Essentially all grib files have a unique name including a date, time, or ID, so we would not link to specific files. The name of the link is also entered, which is what shows up in the Custom download option. An example use of this function is shown in our playlist.
Check grib content Once a grib file is loaded you can double check its contents with cmd+I or menu Grib/Information
Load multiple gribs Use menu Grib/Grib slot x to load a grib into 1 of 3 slots. You can then show any one or any combo. Select the combo you want with the green arrows grib selector icon in the toolbar. Click the icon to step through options. These simultaneous gribs can be wind and current, or high res wind and global wind, or two different models, etc. To see them both on the screen at once they must each have data at the overlapping time selected.
Merge gribs To combine two or more compatible gribs use menu Gribs/Merge gribs then select them on your computer and give the combination a clear name reminding what is combined. This is a convenient option, but then means routing will include all data present. To hide currents if needed, use Force currents to speed 0.
Grib Time

— When you first load a grib file, the top left of the screen shows the Reference time of the grib, which is the synoptic time that the model was run. This will be the first forecast in the sequence. Below that the present time according to your computer.

—The Reference time is effectively a surface analysis at that synoptic time, rather than a "forecast."

Set grib to a specific time

— If you want to just use one of standard forecast times in the sequence (typically in steps of 1, 3, 6, or 12 hr, depending on what you downloaded), then you can use the clock icon (Select grib date). This then shows that forecast without time interpolation.

— For a more specific time in between the forecast times, use grib time stepper in the Toolbar (set step size next to it). You can also set a specific time in the clock icon window.

— Turn on time slider using wind sock icon (click the ball, then move cursor along the line to desired location.

— Time slider extent matches the longest grib loaded, even if only a shorter one is showing, i.e., grib 1 = 1 day, grib 2 = 4 days, then with 1, 2 or 1+2 showing, the slider will be full extent = 4 days.

Force wind

Load a fixed wind speed and direction

This is called Force wind. This can load a wind without any grib or override any loaded wind forecast with a specific speed and direction over the full screen at all times. This is set in the Grib config page (windsock in the tool bar) in the Corrections tab. To exit this mode just shut off the Force wind option to return to the previous grib.  This function can be useful as a training tool to simplify the wind computations, or it can be used tactically, as shown below.

If you are counting on a wind forecast for your routing, but notice that the present wind does not match your observations you can force the wind to be what you see at the moment, and then tell it to slowly blend into the forecast winds over a period of time that you select. Alternatively, you have the option to scale the wind by a fixed amount, but that does not affect the direction.

When the wind is forced, the grib time label, top left of the screen, will turn red. (This does not change color with forced current.)

You can also randomize this fixed wind in a simulation: Boat/Settings/Navigation Simulation mode/Randomized wind.

If you do not have a grib file loaded, and want to force wind and it does not show, then go to the grib config screen at Display tab, and turn on Wind map for the main arrow option.

Force current

You can add current to the full screen with the Force current option on the Grib config page. This will then affect the grib reckoning, routing, and routes, as well as simulation. This forced current then overrides any current data in the grib files.

4.2 Viewing Grib Files 

*** Big section to be completed. Start with the grib config page cmd+G or the windsock icon in the toolbar.

-- Grib config window will not open if no gribs are loaded.

-- Recommend status bar font as Courier New at 85%, so the cursor readout of grib data is easy to read, but obviously personal preference.

-- See Troubleshooting below if no wind shows


Activated slots You can load 1, 2, or 3 grib files, one into each of 3 slots. When more than one is loaded, this is where you decide which is to be in view and active. This setting can be over ridden or even more easily controlled using the 3 arrow icon in the toolbar.
View more than one grib

To view wind arrows from more than one slot, use Grib config page (cmd+G) to change them to different colors, and be sure to have Superimpose arrows from all slots turned on. This works with any parameter that has arrows, but not pressures or other scaler values.

The status bar wind (or current arrow) read out when two or more are showing is for the one with the highest resolution; with same resolution it will be the one with the smallest time steps; and if both are the same, then the one with lowest slot number is used.

Grib time slider

Toggle on or off this option for changing the time of the grib in view. Alternative Grib time changes are with the toolbar clock icon to go to one of the specific files in the grib set or to a specific time which would present an interpolated grib file, or change the time of the grib in view by clicking time steps with the Grib time arrows in the toolbar, whose step size you set next to them.

See video on use of time slider

Superimpose all Does just that. If you have gribs loaded in different slots that have overlapping times and locations then this will show them all. See arrow color options below to distinguish them.
Arrows on grid points This is an important control that lets you prevent wind interpolation between actual grid points. It shows wind barbs where there is actual data. A good truth meter to turn on periodically. A global forecast can appear to have a lot of data when the actual data are rather far apart. GFS data are every 15 nmi; HRRR data are every 1.5 nmi. ten times higher resolution, which in turn means much larger files for the same area if we ask for best resolution. See note on troubleshooting below.
Arrow size an density Experiment to get what you want, Density changes means most when you have the above limit to grid points only turned off. Default size is maybe smaller than you want.
Grib over charts May need to experiment with this if it is crucial to see land borders under the grib, whose presentation changes with background overlays.

These are the color patterns that map out specific values of parameters. Scaler parameters (no direction involved) such as temp, rain, reflectivity, cloud cover are usually presented this way, but wind speed or pressure could as well to give a highlight to the intensity variations.

Gradients on is common choice for a smooth blending between the colors, but it can be informative and often better to turn this off so you see the exact borders between the contours separating values.

If  the background colors appear too dark, maybe in the terminator (showing nighttime), which can be shut off at menu View/Show-Hide/Show Night Zones.  This also varies with charts showing or not.

Query grib data With one or multiple parameters, you can right click the screen and choose Query grib data and you get a window with all data at that point. You can then move the magnifying glass icon around to read data at other locations. Very handy.
Main arrow

Arrows indicate directions of wind, waves, or currents. The three colors possible are for the 3 grib slots, distinguishing them is helpful when more than one is loaded.

Level selection on the right might be need when you have wind data at, say, 10 m (most models), or at 1000 mb (CFS), or 500 mb for winds aloft.

Secondary arrow Main could be wind with secondary being waves or currents. Main and secondary are user's choice. Note there is no barb option on the secondary vectors.
Label The dropdown lets you choose which parameter to label. These might be useful for a quick look, but the display can get congested on the screen. The font type, size, and style of the label are controlled in Configuration/General/Appearance, but this changes all labels used in the charts, so this must be considered. The labels also scale with the arrow size above. It is not often we use this. A color map with gradient turned off might meet related needs.


Read pressure in status bar We see the wind in the status bar at all times, but not the pressure. To read pressure there so you can check out specific points, turn on a background map (see above) of pressure and then it shows up.


No wind shows

Wind, or grib data generally, might not show on first load. If none shows, check the following.

— Must have grib time set to within the range of the grib file loaded. Use clock icon and choose a time.

— The globe icon in the toolbar next to the clock is a grib on/off switch. Be sure it is on.

— With charts loaded, the grib data could be under the chart. Check the setting in menu Gribs/Grib configuration/Display/Gribs over charts is turned on.

— When zoomed in on the display to say 15 to 30 miles or less across, and see no wind with all else ok, then check in grib config to see if you have selected to show "Arrows on grid points" and if so turn that off. For example, if the grib loaded was the stock VLM partial grib then that is GFS wind only at 0.5º which means a true wind arrow only every 30 nmi. And so we might be looking at a region between real data points. With that off, the program interpolates the wind and puts arrows everywhere... this is a good reminder, however, about where there is actual data for specific model outputs. Recall GFS at best is every 15 nmi.

— With two gribs loaded, to see both you must be at a time when both have data. Current forecasts, for example, might be only 4 days, in which case when viewing both wind and current, on the 5th day you see wind but no current. Likewise different model wind forecasts loaded may cover different time spans.

4.3 Meteograms 

— These are graphic plots of weather and ocean data from the Grib file(s) loaded into slots 1, 2, and 3, as a function of time for a specific point on the chart

— Access with a right click on a Grib display at the location you want to compare. The graph starts from the displayed Grib time (top left of the screen) going forward. To see fuller history, set display time to the earliest forecast.

— When multiple Gribs are loaded, it shows data for highest resolution forecast, when data are equal resolution, it shows data with smallest time step, and both of those are equal, it shows values from lowest Grib slot.

— To read digital values, click the plot to get focus there, then hover the cursor over the line. Clicking does not work for this. Hover may take a second to respond.

— When data in different slots start at different times, then this is reflected in the plots.

— Display style is set in menu Config/General/Histogram style. See how these options appear Meteogram Styles

— Compare Gribs is a powerful tool to look at 2 or 3 wind forecasts together. Note the colors of the meteogram curves for each slot do not match those you have selected for the arrows.

— To get digital wind directions, turn on Compare gribs, even if just one is loaded. Or export as CSV.

— Default Export mode is CSV, which provides a clean table of time vs values showing. If you assign extension .csv in your computer to Notepad (PC) or TextEdit (Mac) then any of the qtVlm exports pop open that file at the same time they offer to save it, which can be convenient.

Grib query There is a similar presentation of wave properties in the grib query option. Click the waves tab there to see it.
Mark your spot It can be valuable to know where you clicked for the meteogram, but this is not marked on the chart. So as needed, put a POI on the chart near where you want the meteogram and then click next to it. Won't be able to click right on it; just next to it.
Change parameters — Each tab covers several parameters. Turn on or off ones not needed with the gears button. Click the gear, make your selections, then click the tab again that you are working on from the list above.

— If your meteogram does not show any data, then check the grib time. It could be at the end of the period. Move to the starting time you care about on the slider or clock icon. The plots always start at the displayed grib time.

— You know you have the data and the meteogram shows other parameters, but the one you want does not show. Check the gear icon (bottom left). What you want could be turned off of the display.

4.4 Buoy, station, and ship reports 
Description qtVlm offers a unique presentation of near-live global observations, which are then automatically compared to the most recent grib forecasts loaded, interpolated to the times of the most recent reports. Buoys, statios, and ship reports are all available with a single right click. With different models loaded into the 3 grib slots you can compare competing models with the actual observations to evaluate best model for the conditions.
Buoy and station reports

1) For any point of interest on the chart, right click and choose Weather stations download. This will load a set of marks onto the chart, one for each report category you requested that is within the range you selected of the point clicked—the default is 300 nmi. Data available might include the latest wind, pressure, sea state, sea temp, as well as sea state at some buoys, all of which is stored with each of these weather report marks. A cursor over the station label reveals the data, as well as a comparison with forecast models you have loaded. Note this is a tooltip access, not a click. The distance and direction to the station from the boat is also given. Sea temp can be valuable for evaluating tropical storm production, even when wind is not available.

2) The density of stations varies notably around the world. If you move to another location and ask for reports it will add them to the ones you have. Delete them first if not of use (see below).

3) Set the range of reports (miles from clicked position) and the type of report at menu Configuration/Gribs and harmonics/Harmonics and weather stations at the bottom of the page. Meteo France is an extensive set of reports, but only in France. Outside of France it can be shut off. The others are global. Metars are international airport weather; NOAA are the buoys from NDBC (our primary source), mostly around the US but broadly scattered elsewhere; Gowind ( is a network of land based weather stations similar to those supported by users of instruments. These are not official sources, usually well inland, but folks running these do care to do well with what they report.

4) The time of latest data at each station can vary from minutes to an hour or two. We have to learn by direct experience or look up the stations of interest to learn the update times. Airport data are typically every hour. NOAA buoys are typically every 10 minutes. Ship reports are usually every whole hour.

5) To update reports, just ask for them again. They will overwrite what is there with new report data. Note that ship reports are only located to the neared 0.1º of lat and lon, which means their actual location is about ± 3 nmi.

6) Beside the obvious value of knowing actual conditions at specific points, a key value of the reports is to use them to evaluate a model forecast as discussed below.

Compare reports with model forecasts

1) You can load up to 3 different model forecasts in grib slots 1, 2, and 3. When you do a tooltip on a station or ship report you see the time of this latest report and at the bottom there is the equivalent grib forecast for that time and place, assuming you have gribs that overlap in time. When reports and grib downloads are obtained at about the same time, this will always be the case. The report time is not likely to be an exact grib time in your forecast, but the program will interpolate the data for the report time.

2) There is only one grib report shown, so if there are more than one loaded, and showing (more than one green arrow showing in the grib slot icon in the toolbar) the report has to choose which one to use in the report. The first choice is to compare the forecast with the highest spatial resolution—a regional forecast would be chosen over a global forecast, because it always has higher resolution. If the models loaded have the same horizontal resolution, then the comparison will be made with the one that has the finer time resolution—data given every hour will be used over that with only every 3 hr or every 6 hr forecasts. If both space and time resolution are the same, then the model shown will be the one with the lowest grib slot number.

3) To compare the observations with a specific model, which is an important power of this tool, just turn on one grib slot at a time with the green arrows and the comparison will be made with that. To confirm that this is working properly, read the report time, then set the grib time to match that, then place the cursor right on the report mark and read the wind in the status bar to see that it matches that used in the report.

Delete reports Use menu Marks/Remove marks by type/Weather report. This is used for all types of reports. Note you are deleting them here, not hiding them. To get latest reports request again as above. This also removes all of them. If you want to save a few, then you can use marks manager (cmd+M) to selectively delete some, and archive others if desired, but these will be overwritten when new data is requested. Overwritten means all that exist get deleted and what is new gets added.
4.5 Graphic Weather Maps and Images
Procedure 1. Menu Grib/Weather Images/Open a Weather image
2. Choose one of the 8 configurations to set up
3. Activate it and unlock it.
4. Under Browse choose the image: this can be a link to any graphic file on your computer, or a direct URL to the image Online, or it can be a KML file that includes image, georeference data, and online source (see our video on this KML process).
5. For image files (not needed for KMLs) enter coordinates of top or bottom left corner, and then the range of the Lat and Lon. These do not have to be precise, as we can then adjust, but it is easier if they are close. Set Transparency to halfway.
6. Click OK, then use corners to adjust to proper scaling using base grid. Then return to Grib/Weather Images/Open an Image and lock the image in place.

-- reminder, be sure to Activate the one in use
-- remember the slider for adjusting transparency once in view
-- georeferencing data for images are stored in the [faxmeteo] section of the qtVlm.ini file. For time being it is best not to edit them there.
-- can move corners or grab the center to move whole image.
-- For small areas, you can make it in GE then use the KML file, which does all the work for us... but for large areas, this won't work well because the GE projection is unique and not compatible with mercator used in qtVlm.



View NetCDF Load the NetCDF file (.nc) into Panoply and create the image you want to see in qtVlm (make it a large one), then export as KMZ and import as above. This will auto load the georeferencing and cut off all the labels and color bars.
Auto update When the desired image link has a URLs to files that keep the same names, we have a very convenient way to display the data. Load the url to the image into Google Earth and then once it displays, save as KML, and then import. Good products for this include all NOAA weather maps, ASCAT satellite winds, Navy Gulf Stream analysis, and others.
Troubleshooting If your image does not show up, check that it is activated. This is easy to overlook if you are working with multiple images.
4.6 Reserved
4.7 Compare Models
Background We can compare the wind speed and direction forecasts for up to 3 models for a fixed time over a large or small area, or for a given point, compare them over time. When two models agree we have more confidence in the forecast, but that is no guarantee. A better check is to compare the model to the actual winds using ASCAT data or ship and buoy reports.
Area view

In Grib/Grib config make these settings:

1) turn on (ev everything!) All slots, color legend, display slider, superimpose all, arrows on grid points

2) size and density to about 3/4 full plus grib over charts, but we do not need charts for the model comparisons.

3) Background = none

4) Main arrow color: set grib 1, 2, 3 to have different arrow colors. I use red, white, and blue to remember which is which when looking at the plot. With barb.

4.8 Forecast Zones
Background The NWS has 3 marine zone categories, Coastal, Offshore, and High Seas. The first two are divided into subcategories. There is a text forecast for each of these that is updated every 6 hr. qtVlm can show where these zones are located and give the ID of each. With that in hand we can request a forecast from Saildocs, or even set up a subscription to have it mailed to us regularly. The zones display is done via shapefiles.
Download the shapefiles Use this link NWS Marine Zone Shapefiles.  Then make a folder on your computer called Forecast zones, and inside that 3 more folders called Coastal, Offshore, and High seas. Then download the files and put them into the right folders. You do not need to unzip them.
Load the shapefiles Use menu View\Shapefiles and SHOM\Open a shapefile. Then browse to the file you want to load, load it and choose legend key = ID. Then a cursor over the zone will tell you its ID.
Request forecast from Saildocs

To get the latest forecast, send an email to query at with the simple message send ID, such as:

send PZZ820
send PZZ920

where these are the IDs of the two zones you want. Read saildocs instructions to see how you can subscribe to have these sent automatically.

4.9 Waves
Background The GFS model forecasts nine wave properties covering wind waves and swells, and statistical combinations of these two. These parameters can be requested separately as needed from Saildocs. See our note on Routing with Wave Forecasts. Six of these forecasts are scalar values such as wave heights or periods and three of them are directions: swell direction,
5.1 Technical 

Times are stored are in units of time since epoch (seconds since 01/01/1970 00:00:00).

Key files for settings: boatAccReal.dat, poiReal.dat, qtVlm.ini. See notes on Backups.

Crashes when doing fast chart scale changes Check that you have the Chart memory size set to Very High on the menu Configuration/Charts/Memory allocation. Setting this has solved most similar issues.

— polar on boat set with compass? Show/hide speed polar
— hide compass with option / alt and C


— Traces module: Addition of the PPC (Polar Percentage) in the exported data.

— hide vessel icon general settings you can hide the microboard



Extended view

In the configuration window there is an option to turn on OpenGL (open graphics library). This could in principle enhance the graphics performance, but it is not certain to cause any effect. If there is any question about graphics perforamance, then try with this on or off. The effect of openGL on might be the biggest when you are using course up display, which is frequently rotating the whole chart in view.

Extended View allows qtVlm to draw in advance charts outside of the screen, which will improve panning but might slow down a bit the rendering. Like openGL, this is check to see if it helps or hurts.

Screenshot cmd+E or ctrl+E takes a screenshot of the qtVlm screen and saves it to the root qtVlm folder as screenshot.png. Each time this is done it overwrites what is there. Note, however, that with OpenGL turned on this will likely just be a blank screen. Turn that off to use this function — or use the varous built in ways to take screen shots that are native to Mac and PC.
5.2 Backups 
Suggestions If you do by accident delete the whole program or for any reason need to reinstall from scratch, you may want to have backups of your marks, routes, and other data. There are folders for each of these categories in the root qtVlm folder, but we recommend that these categories of your personal data be stored in a different folder: charts, grib files, POI images, polar diagrams. Dynamic objects in use such as pathways, barriers, marks, and so on can be periodically backed up as outlined below. See data folder suggestion below.

Protective backups



There is no way with even the best modern computers and software to avoid a periodic crash or hang up, so for navigation software we need belt and suspenders! First be certain that track recording is turned on (qtVlm/Config/Boat/Track) with no time limits and high accuracy (you can fine tune that later) and with autosave set to the 15 min or your choice. Then periodically Export your full set of data in menu qtVlm/Export qtVlm data. This first gives the options to export (underway choose all) then it writes a file in your root qtVlm folder called If the program or Windows crashes or locks up for any reason, you reboot and then use menu qtVlm/Import qtVlm data and select this zip file. Then you are back on air as you were when you lost connection. Periodically maybe save this zip to a thumbdrive.

An even faster way to protect a lot of set up time or crucial bit of navigation is just to do a save all with the keys cmd+S for mac or ctrl+s for PC. This is the same as save POI discussed below, but it is actually saving all your configuration of instrument layouts, charts and scales in use, and so on. It is just the same as shutting the program down and turning it back on. Thus after any long set up process you do not want to repeat, do a quick save all this way.

Note this is not the same as the Export data above. That is actually backing up the data themselves, including polars and gribs. The Save all assumes the data are all in place and safe, but you just want to lock in the work you did in the present set up. Experienced uses of any nav program, always save all fairly frequently.

With that said, the qtVlm team does ask that if you ever do get a crash or lock up to please send the info to them and they will track it down and fix it.

Full backup Another approach is just to compress the full root qtVlm folder and move it to a safe place like a thumb drive. This is quick and easy security when headed offshore. Back up your data file in the same way, see below.
Save POI, routes, and barriers After making any of these that may have taken some work, you can back then up with cmd+S or ctrl+S. This step saves marks, routes, and barriers. Also access from menu Marks/Save POI and routes, which is where you load them back if saved this way.
My qtVlm data folder One idea is to make a folder called My qtVlm data and in it have subfolders for My Charts, My Gribs, My Images, My Harmonics, My Shapefiles, etc. Then this one folder can be backed up for security.
5.3 Mobile Apps 

These apps work remarkably like the computer versions and once familiar with those, the mobile are easy to use. We do not use these in our courses, and have not experimented yet with using them with the same content we use in the course. The ability of the apps to broadcast by wifi all of the sensor data they include is a very attractive feature being a real backup to GPS, heading sensor, heel, and barometer.

iOS and Android Find these in the iOS App Store and the Google Play Store on your mobile devices. Unlike the computer versions, the mobile versions are commercial products.
5.4 Shapefiles 
Background These are vector files of various GIS data, such as various city, county, and state borders, roads, elevations, and various other things of interest to navigation, cited below. qtVlm has a uniquely versatile way to load and display these.
Examples US sources include:  Elevation contoursInternational Maritime boundaries, NWS forecast zones,  Gulf Stream Boundaries, plus Extensive data on France (SHOM) discussed in the qtVlm Manual.
Sample See: Adding Elevation Contours to qtVlm, which is an article with video. Once a shapefile has been loaded you do not have to load it again; they are stored in the root directory/shapefiles and you can call them back from that location.
5.5 More Support 

Get more help

Ways to post a question

The qtVlm User’s Manual is the main reference for the program. That file can be searched, just as we search this one.

We offer in depth online training and resources that go into the details of electronic chart navigation and marine weather analysis and routing. The ENC course also includes much specific information from the S-57 and S-52 standards.

If you are taking a Starpath online course then please post your questions on qtVlm in the Student Discussion Forum.

The public can read our Public Discussion of Electronic Chart Systems, but to post there you must have an active webcard, which includes notable benefits beyond the Discussion Forums.

Starpath students are reminded we have an interactive list of assigned videos and articles within the Electronic Chart Navigation Course. These are numbered by lesson; they illustrate most, if not all, of what is on this cheat sheet.

Online there is also an English language qtVlm Facebook User's Group, which is open to the public (may need a Facebook account?). Remember, too, that there are many qtVlm posts on FB in other languages, but the Chrome translation option works well in most cases.

5.6 Alarm Details 

Use of the
Ruler tool
to sense the alarams






Red Obstructions










plus nuance on shallow water contour selection

Predictor or reckoning alarms are either dangers or obstructions depending on the nature of the objects and the contour selections. Use Caris online object catalog to translate object abbreviations, included here so you can search for them if desired.

You easily tell what category of alarms are around you with the ruler tool. Just turn it on and sweep across the chart. It will turn orange or red according to what it crosses — orange, going across a danger (ie safety contour) or red going across an obstacle (ie the shallow water contour, coastline, or green foreshore).


Objects at or above sea level are obviously obstacles. It includes FLODOC, PONTON, SLCONS, ICEARA, HULKES, LNDARE (with geometry Polygon or Line), UNSARE that are not Points, LAKARE, LOGPON and obviously COALNE. Note that FLODOC, PONTON, SLCONS, HULKES, LOGPON that have a geometry Point are excluded and will be in the Dangers category only.

DEPCNT if less than or equal to shallow water contour requested setting. This is a case of a requested contour value having a significance other than the base for searching for the exact or next deepest native contour. (Example, chart has contours at 5, 10, and 15m. You request 7m for shallow contour. The 10m is displayed on the chart, but you get the alarm only when crossing the 5m line. See nuance below)

DRGARE with sounding less than or equal the requested shallow contour (with some special case exceptions).

SOUNDG (sounding) less than or equal to shallow water contour requested setting.

UWTROC, OBSTRN (point) and WRECKS with WATLEV = 4 (covers and uncovers) or 5 (awash).

UWTROC, OBSTRN (point) and WRECKS with WATLEV = 3 (always underwater) with a known sounding less than shallow water contour.

In addition to the above standard obstacles you can optionally add other zones to be blocked, ie they not just stop a simulation or go red with the ruler tool, the optimum routing routines will not cross them. You choose these extra ones at menu config / charts / rasters and vector in the bottom right corner. There you can add traffic areas, restricted zones, and so on.


DEPCNT if less than or equal to the active safety contour.

SOUNDG (sounding) that are not an obstacle, but less that activated safety contour. This would be an anomalous sounding of, say, 15 ft found outside of the safety contour set at 18 ft. Normally a depth contour of 18 ft includes all the soundings of 18 or less ft, but we do periodically see these exceptions.

UNSARE that are points.


UWTROC, OBSTRN (point) and WRECKS with WATLEV=3 and with a known sounding less than activated safety contour and not being already an obstruction.

UWTROC, OBSTRN (point) and WRECKS with WATLEV=3 and with a unknown sounding.

Nuance on shallow water contour selection: Because of the way NOAA encodes the feet to meters conversion (see textbook), when display units are selected as feet, we cannot request, for example, 18 ft to get the 18-ft contour, we have to request something less such as 17 or 17.7. But that means we requested one that is not there, so the effective safety contour (that effects alarms, routings, and groundings) will now be the next shallowest, which could be 12 or 6... or 3 or 0, whatever happens to be the next one down. Thus if you want to use a specific contour on a US chart for a shallow water contour with the color change and alarm occurring that specific one, then switch to meters, do a chart info check to see how the contours are identified and then ask for the one you want in those terms, i.e., to get 18 ft, you request 5.4m. (5.3 or 5.5m will not work!)

5.7 Restore Complete Version 
Restore in iOS mobile version To transfer a purchased iOS version to another iOS product, we download the free version and then use menu qtVlm/Restore complete version. This assumes you are logged into the device with the same apple id that was used to purchase the app, and more specifically it must be the same form of the id. Apple accepts [email protected] and [email protected] symmetrically for many functions, but not for this one. The format in place must be the one used to buy the app originally, else restore will not work.