Towards More Reliable Estimation of GPS Positioning Accuracy

Uncertainty of vector components estimation, obtained from processing GPS data using either commercial or scientific software, represents rather an internal consistency than the accuracy of positioning. Short period biases, including non-modelled effects, some with unstable amplitudes, that affect GPS solutions are as systematic-type terms not reflected in uncertainty estimation. Therefore, calculated uncertainty is usually much too optimistic as the accuracy estimate. In the routine GPS data processing one observing session provides a single solution. Data that form such observing session can be represented by a series of overlapped sessions. Comparison of solutions obtained from processing overlapped sessions leads to more reliable accuracy estimation than the one based on uncertainty estimation of individual solutions. The strategy of GPS solutions quality analysis based on the concept of overlapping sessions with optimum length and temporal resolution is presented. The strategy was verified with use of data from the EPN stations processed with both Bernese and Pinnacle software packages.