Atmospheric Moisture Estimation Using GPS on a Moving Platform

S. Skone, Y. Gao, O. Al-Fanek, W. Tao, Y. Zhang, P. Héroux, P. Collins

Abstract:	GPS signals experience range delays as they propagate through the neutral atmosphere. These range errors are dependent on pressure, temperature and humidity along the signal path. By removing all other sources of ranging error, the effects due to atmospheric moisture may be isolated and estimates of zenith wet delay (ZWD) derived from GPS observations. Typical methods for ZWD estimation are based on postmission software operating in near real-time (e.g. Bernese, GAMIT). The real-time availability of precise GPS satellite orbit and clock products has enabled the development of a novel positioning methodology, however, known as precise point positioning (PPP). Based on the processing of undifferenced pseudorange and carrier phase observations from a single GPS receiver, PPP provides a new way to perform real-time ZWD estimation. A real-time PPP software product, P3®, has been developed by researchers at the University of Calgary. Recent advances in this PPP approach allow simultaneous estimation of position and ZWD in kinematic mode. In this paper, several tests are conducted to evaluate the feasibility of employing real-time PPP techniques for ZWD estimation in kinematic mode. Initial experiments are conducted using a static receiver, with known coordinates, to evaluate the limitations in kinematic processing. Further tests are conducted for ZWD estimation using a vehicle. Results for both the static and vehicle tests are compared against local truth data obtained from a water vapor radiometer. ZWD accuracies are at the 1-2 cm level. Data from an airborne platform is also processed for ZWD estimation using PPP under high-dynamic conditions. The feasibility of vertical moisture profiling is evaluated, where successive estimates of ZWD are differenced during the ascent phase of flight such that the amount of atmospheric moisture in discrete vertical layers is computed directly. Truth data are derived from highresolution regional numerical weather predictions provided by Environment Canada. ZWD accuracies are at the cm level for the airborne tests, and relative vertical profile accuracies are at the 20-30% level for the lower altitudes.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	1891 - 1901
Cite this article:	Skone, S., Gao, Y., Al-Fanek, O., Tao, W., Zhang, Y., Héroux, P., Collins, P., "Atmospheric Moisture Estimation Using GPS on a Moving Platform," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 1891-1901.
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