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The Interactive Computer Ephemeris (ICE) is the Naval Observatory's original computerized nautical almanac. It is a bit clunky to use, and takes a while to learn how to use (there are numerous computations to choose from) but does give good data at least in all the cases we have tested even though they no longer support it, nor guarantee the results. This is the same program sold commercially by some outlets, offered free of charge here as a bonus to Starpath customers. Once you log in with your webcard, you will also obtain valuable instructions for using this rather obteuse resource. For a much more convenient computerized almanac, we recommend the Starpath Perpetual Almanac, which goes backwards in time as well as forward, 1560 or so to 2100.
Long list of planetarium-type software
Comprehensive compilation of star-map and related astronomy software. Many samples of shareware and freeware, along with commercial versions as well.
PC -Time sync
Free software that sets your computer to the correct time. The sync software listed here is all we know of (ie way more than you need), many have various features besides time sync. The active presentation includes recommendations and procedures.
Star map Cartes du Ceil
Certainly one of the best available. Many options for astronomers as well as navigators. This is a freeware product. The fine work of Patrick Chevalley in Switzerland.
Star map Home Planet
There are several of these, commercial, shareware, and freeware. This freeware product is as good as most of the commercial ones. This freeware product from John Walker in Switzerland is quite a powerful program. No installation, just download, unzip into a folder and run. Has a neat screen saver option as well.
Star map Skyglobe
There are many star map programs on the market and in the shareware/freeware realm, some quite elaborate with many options. But for all the standard applications that might be of interest to celestial navigation, we have not found many better than this classic DOS program. It is still our favorite. Learn the easy keystroke commands and you have a most wonderful tool here. However, one should still see the elegant Cartes du Ceil for the top of the line. This one is just a bit easier to use in some situations. (There is a windows version of this program, but it does not work too well, since modern computers are way too fast for it.)
General Navigation
Computes magnetic variation anywhere in the world including annual change and dip angle, along with all other properties of the magnetic field. Data are available for dates from 2000 to 2005. After that you can download a simple file to update to 2010.
GIS info
All about Geographical Information Systems in the US. Maps, charts, photos, elevation data, related software for viewing, etc.
NIMA Navigation Computers
This is a Starpath "repackaging" of the NIMA nav computers that they prepared for the American Practical Navigator CD. They are also available online, but not in this nifty, small, single file format. It includes one computer for each of the 32 tables of data in Bowditch, plus sight reduction and sailings, Mercator and Great Circle. Very slick.
Precise distance computer
This technical program computes the true distance between two points on the earth taking into account the actual geoid shape that is selected. Note that typical great circle or rhumbline programs presume that the earth is round which in fact is an adequate assumption for typical marine navigation problems. This is only for those interested in the nitty-gritty, or for studying the effects of GPS datum variations. Also computes new lat/lon after moving given distance and direction from another point, ie high precision DR computation.
All about NMEA data
Explains data structure, etc. Plus other links provided here.
DR Simulator for GPS
GPS simulator for use with Windows echart programs and for Pocket PC nav programs, such as Memory Map and MapTech, and others. Enter set and drift, course and speed and it will emulate NMEA string for SOG and COG.
Live locations of GPS satellites
An online service from Stanford University shows where all GPS satellites are located. Page updates every minute or so. Plus other valuable info on GPS, WAAS, etc
Big red cursor
Very nice large red cursor for use with echart programs or other applications. Install and uninstall instructions provided.
High precision DR computations
This online computer has two functions: 1 compute accurate great circle distances, and 2 compute accurate DR position given a known position and a course and distance sailed from it. It will let you enter the shape of the earth for highest precision. Use WGS84 for best results. See our article on this topic in the Articles section.
Nice screen saver for PC
This freeware screen saver shows a map of the world with your location at the center and then outlines what part of the world is in daylight and dark and shows the location and phase of the moon. It keeps up to date automatically. Very nice.
Morse Code
Several versatile programs available here for translating and generating Morse code. Some are better suited for training, others for actual working tools.
Tides and Currents
For Palm OS
Very nice, postcard freeware (send the author a card if you like it) program for handlelds computes tides worldwide and current stations in US waters for Palm OS. Will not work on Pocket PC (Windows CE).
For Pocket PC
Freeware program for hand-helds, computes tides worldwide and current stations in US waters for Pocket PC and other Windows CE devices.
For Windows
There are several ports of the original Dave Flater unix xtides program, this is one Windows version, with links to others. (xtides is the basis of most subsequent tide and current programs. See full list of ports at xtides32 site... this program is certainly not as nice as some commercial ones such as Nobeltec's Tides and Currents for Windows, but the price is certainly right for those on a strict budget. This data is also available online -- see Inet Connections.)
Grib map viewer
Grib files are vector renditions of weather maps, available 4 times a day. They are highly compressed and easily accessible by HF or landline email or internet. This freeware product decodes and displays the maps. Grib files are explained in the Articles section.
Starpath TrueWind
True Wind from Apparent Wind. A small but very effective program that computes true wind speed and direction from apparent wind speed and direction and boat speed. Offers numeric input or a unique graphic interface that shows exactly how the vectors look in the computation. The program works very much like the java version of Starpath TrueWind, but the downloaded program is faster and smoother, with more options.

Also included is a tutorial on the role of true wind computations in navigation and weather analysis, along with step-by-step instructions on how to solve the problem graphically.