Self-Calibration of Pseudorange Errors by GPS Two-Frequency Receivers

Gregory Bishop, Andrew Mazzella, Elizabeth Holland

Abstract:	GPS applications continue to seek greater accuracy, driving continued improvement in capability to calibrate and correct pseudorange errors. Recently there has been significant progress in reducing pseudorange errors from mjor sources such as multipath and satellite group delay. However, the receiver system calibration errors may not have received due attention. Where sub-nanosecond accuracies are sought, doubt may remain after application of existing techniques. How well is the “calibrator” calibrated? What error sources aren’t included? Has anything changed since calibration? For example, changing the antenna system has been shown to significantly alter the pseudorange error of the overall receiver system. Bench or internal calibration of the receiver alone would not compensate for this. Herein we describe a method that can calibrate an installed systemfor the combination of all system components’ contributions to pseudorange error. This method would contribute to overall system integrity, since it can detect drift in a receiver or pre-amp, changing of a pre-amp or antenna, or a change in a satellite error that would otherwise go unnoticed and increase navigation error. This method for Self-Calibration Of (pseudo)-Range Errors (which we are initially calling “SCORE”) was first introduced for its capability to monitor the satellite group delay errors. We believe this SCORE method is unique in that it uses the ionosphere as a constraint on the GPS measurement calibration. SCORE will allow an individual two-frequency GPS receiver system to autonomously maintain its pseudorange accuracy without use of any hardware calibrators or ionospheric models.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	251 - 259
Cite this article:	Bishop, Gregory, Mazzella, Andrew, Holland, Elizabeth, "Self-Calibration of Pseudorange Errors by GPS Two-Frequency Receivers," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 251-259.
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