The Drift Sight was a bombsight developed by Harry Wimperis in 1916 for the Royal Naval Air Service (RNAS). It used a simple mechanical device to measure the wind speed from the air, and used that measurement to calculate the wind's effects on the trajectory of the bombs. The Drift Sight eliminated the need for a stopwatch to perform this calculation, as on earlier devices, and greatly eased the bomb aimer's workload.