Position plotting with card plotter...
First you have to make a plotter as described at the end of these notes. Next you must prepare your charts with a few extra meridians and parallels over the region you will be traveling, also described at the end.

There is obviously some time involved in this preparation to use this method, but once completed it lasts for a long time and will speed up your accurate position plotting by a great deal on the charts that apply. For tricky passages or for racing navigation where quick navigation is essential, this simple method has proven extremely valulable many times now since the advent of digital read outs, back in the old LORAN days. With it, and very little practice, you can plot an accurate position on a chart about as fast as you can read them from the electronics.

Video Notes
In this example, we plot: 48° 23.25' N, 122° 33.82' W on a chart with scale of 1:25,000. This method requires a separate card, or at least corner of a card, for each chart scale it will be used with (explained below).

Step 1. Align the right side of the card with the nearest meridian of whole minutes of longitude of your position, in this case 122° 33'. (This meridian has to be on the chart. If it did not come that way, then this is one that we had to add ourselves, as was done in this case, in red.)

Step 2. Slide the top edge of the card up to the nearest parallel of whole minutes of latitude of your position, in this case 48° 23'. Then slide it farther up to match the decimal part of your latitude, in this case 0.25'.

Step 3. Count left, to the west, from the meridian along the top edge of the card to mark the decimal part of your longitude, in this case 0.82' and mark your position with a point. Then it is a good idea to immediately label this position with the time it was valid.

How to make a "Starpath" card plotter
We (humbly!) call this a Starpath plotter so that this particular method is easy to refer to. There are numerous plastic plotting aids on the market, but we have not seen any like this, and we have not seen any that work as well. Furthermore, it is a valuable exercise to construct the device and plot the extra chart lines as it gets the user a bit more involved with the actual scales being used.

Use any piece of cardboard. Index cards work well — we have many times cut the back out of a notepad to make the cards. Next study the chart you will be using for this to see what the decimal scales are for latitude and longitude. Generally this method works well for the common scales of 1:40,000 and 1: 80,000 charts or 1:25,000. For larger scales it works even better, and for smaller scales there is not much need for this type of plotting.
Note from slide 2 that you mark the latitude scale going down the right side and the longitude scale going across the top to the left. The scale should be marked in decimal degrees, which in turn means it is most convenient when the GPS output is in decimal degrees — as opposed to degrees, minutes, and seconds, which is awkward to plot.

A separate card or corner is needed for each chart scale used. Also the latitude and longitude scales must be divided into tenths, which is not given on all charts. The nautical miles scale will do it for the latitude, but you will have to interpolate the longitude on some charts, with 6" = 0.1' etc.

Since most charts do not have parallels and meridians drawn every 1', we usually need to add extra lines to use with this plotter. Once added, it is helpful to label them in the vicinity of your travels. Needless to say, we should double check these labels with the chart scales themselves.

Once prepared, this is a fast, convenient, and accurate way to plot. Time spent in preparation and practice should prove rewarding. Again, though, this is intended for fast plotting in somewhat special circcumstances. For most routine navigation, simple use of parallels and dividers, covered elsewhere in this plotting tutorial, should do the job just fine.