CPM-1 Ground Speed Calculator (nautical miles, 1:500,000)

The secret of spoton ETAs for VFR pilots!

Simply place the calculator at your position on the map and, using the appropriate ground speed scale, and read-off the time to the desired point or distance. Alternatively use by recording the elapsed time over a known distance to calculate ground speed. Usable at ground speeds from 50 knots to 140 knots and available for 1:500,000 scale maps. this ingenious gadget could be the most useful plotter in your flight bag.

(nautical miles, 1:500,000)