The feasibility of developing a speed measurement technique employing passive microwave sensors has been investigated. The system would employ dual radiometric receivers, located at two positions in the direction of travel, to detect microwave energy radiated or reflected from the terrain (grass, crops, plowed fields, etc.). As the system moves along, varying but similar signal levels are detected in each receiver. The receiver outputs would be cross-correlated and the time delay between the signals would permit the calculation of speed. No signals would be radiated (transmitted), thus avoiding problems relating to emission of radio frequencies and the attendant requirements for frequency assignment and licensing. For this investigation it is assumed that the system is to be carried on a ground vehicle, such as a tractor or a tank.
James C. Wiltse, James C. Wiltse,
"Radiometric ground speed sensor feasibility", Proc. SPIE 1929, 17th International Conference on Infrared and Millimeter Waves, 192924 (14 December 1992); doi: 10.1117/12.2298193; https://doi.org/10.1117/12.2298193