Differential doppler velocity GPS receiver.

摘要

To reduce error introduced by a local oscillator (26) in the velocity calculations, the receiver has two "tracking channels" (98, 110) and a microcomputer (70). With numbers required to, simultaneously, lock each of the "tracking channels" each to a respective satellite signal, the microcomputer (70) employs a differential doppler technique to calculate the receiver velocity. The microcomputer calculates a number which represents the difference between the apparent doppler frequency shift of the carrier signal which is transmitted by the first "tracking channel" (98) satellite and which is measured over a specific time period and the apparent doppler frequency shift of the carrier signal which is transmitted by the second "tracking channel" (110) satellite and which is measured over substantially the same time period.