On the afternoon of October 19, 2013, James Rodgers took a stroll through Myles Standish State Forest, a swampy area of protected land that lies about five miles south of Plymouth, Massachusetts. It was a perfect day for a little ground recon. When Rodgers stopped to look at the topo map on his iPhone, the screen showed the concentric whorls, geographic cowlicks, elevation, and sink of the surrounding forest of mixed oak, red pine, spruce: a good range for the quadcopter.

What he was looking for was flight suitability. Whereas fixed wings need room for takeoff, quadcopters require thin ground…