Real-Time Point-Positioning Performance Evaluation of Single-Frequency Receivers Using NASA’s Global Differential GPS System

This paper evaluates the real-time positioning performance of a single-frequency receiver using the 1Hz differential corrections as provided by NASA’s Global Differential GPS (GDGPS) System. While a dualfrequency user has the ability to eliminate the ionosphere error by taking a linear combination of observables, a single-frequency user must remove or calibrate this error by other means. To remove the ionosphere error we take advantage of the fact that the group delay in the range observable and the carrier phase advance have the same magnitude but are opposite in sign. A second way to remove this error is to calibrate the ionosphere with a real-time database of grid points computed by JPL’s RTI (Real-Time Ionosphere) software. In both cases we evaluate the positional accuracy of a kinematic carrier phase based point-positioning method on a global extent.