The Wright brothers measured many of the flights of the 1902 glider, taking data for time, windspeed, distance covered, and the slope of the sand dune.

From these measurements, they could calculate the airspeed (windspeed + ground speed, which is distance/time) of the glider, the lift-to-drag ratio, and other aspects of the glider's performance. It is not known whether or not they compared this data with the predicted performance of the glider, but the results convinced them that they could build successful flying machines from the data they had recorded.