Estimation of error correlation distance for differential GPS operation

A method for increasing DGPS (differential Global Positioning System) accuracy and operational coverage by adaptively compensating for the changing pseudorange error spatial correlations is presented. These spatial correlations change with time due to atmospheric and geometric variations. Two algorithms for estimating the spatial correlation distances at each ground station are presented. These correlation distances are used in the user receiver´s Kalman-based optimal solution of the pseudorange measurement compensations. This increases the operational range and position accuracy by properly accounting for the varying GPS error correlation distances between the ground reference receivers. Simulated examples are used to demonstrate the implementation of this DGPS method. Results showing the added improvements of this approach compared to the constant correlation distance approach are presented. Limitations and suggestions for future research are also discussed