Differential GPS with latency compensation for autonomous navigation

Differential global positioning system (DGPS) techniques are frequently used to correct for ranging errors common to two receivers, one of which is at a known position. A time delay (latency) is inherent between the generation of pseudo-range corrections and their application by the user. Such latencies can result in large residual errors. The latency issue is especially important in applications where the corrections are sent by a low bandwidth channel. DGPS corrections are also available commercially at a cost, but also lag behind standard GPS data. For online applications, such as navigation for autonomous vehicles, the data latency of the DGPS correction is a fundamental limitation on DGPS performance accuracies. These corrections can be predicted for relatively short periods of time. In this paper, an innovative methodology is developed which predicts the corrections and compensates the GPS data in real time. It also takes care of any transients in the DGPS data in real time. This methodology is being applied to automobile navigation and tested in a DGPS/INS system.