The first aircraft plotter was invented by a Naval officer named Weems. He adapted the much larger shipboard plotter into a plastic model which was like a ruler with an arc of 180-degrees in the center. The ruler itself had measures for the WAC and sectional charts in both nautical and statute miles. A post-WWII improvement was to make a rotating azimuth dial with arrows indicating the route direction. Until recently all plotters were of a plastic that would be destroyed by heat. Protect any plotter from the sun.