Measurement of ground speed with a radial grating

Abstract

This paper describes a device capable of measuring, with very high accuracy, the ground speed of a moving carriage. The device employs a 6000-line radial grating combined with a simple optical system and a photoelectric circuit. The electrical output is fed to a frequency and time measuring instrument, which compares the pulses with a crystal controlled time base and displays speed as feet per second with five-digit accuracy.