This piece originally ran in the June 2020 issue of EAA Sport Aviation magazine.
Long before ForeFlight, AnywhereMap, or even GPS, a company called Thompson Designs in Addison, Illinois, came up with a moving map display for GA pilots. Introduced in 1965, the Pathfinder Flight Visualizer looks a bit like a Star Trek tricorder, with a bigger “screen.” It’s a well-engineered box that consists of a sectional-type chart that scrolls to simulate the airplane’s ground track. The device has no actual position information. Instead, it uses what amounts to mechanical dead reckoning, moving the bug based on the groundspeed set by the pilot. It originally retailed for $89.95 (about $750 in 2019 dollars when counting for inflation), and the printed chart inserts cost 75 cents each. By all accounts, it wasn’t a big seller but was certainly an idea ahead of its time in some respects.