National standards for horizontal and vertical accuracy of topographic maps were adopted in 1941. the standard for horizontal accuracy requires that no more than 10 percent of the well-defined map points tested shall be more than 1/50 of an inch out of correct position at scales of 1: 20,000 or smaller.

for maps of scale 1: 24,000, 1: 62,500, 1: 250,000, and 1: 2,000,000, 1/50 of an inch on the map corresponds to how many feet on the ground?