Kinematic Positioning Using Adaptive Filters and Multiple DGPS Receiver Configurations

The accuracy of trajectory determination by differential GPS (DGPS) is limited mainly by receiver noise, atmospheric errors, orbital errors and multipath. Independent estimates of a trajectory can be obtained if several reference stations are used to generate differential corrections. Using these estimates and an adaptive filtering system it is possible to estimate, characterize and remove some of the errors mentioned above.The objective of this paper is to introduce the adaptive filter as a means of estimating and reducing the errors that influence the accuracy of a trajectory determined by DGPS. An analysis of trajectory estimation for an aircraft using a multiple DGPS receiver configuration and an adaptive filtering system is described. Data collected during an airborne survey carried out over the Canadian Rocky Mountains is used in the analysis. Four ground-based reference stations were spread out over approximately 100 km, providing independent estimates of the trajectory of the aircraft.It is briefly reviewed how an adaptive filter can be used to estimate the correlated part of two discrete-time signals. Since the true trajectory of the aircraft is the underlying signal in each of the four estimates, the adaptive filtering system proves to be a useful tool for the determination of that trajectory and the effect of the errors that influence it. Examples from the analysis are used to demonstrate the effectiveness of the technique.