Improved Tropospheric Delay Estimation for Long Baseline, Carrier-Phase Differential GPS Positioning in a Coastal Environment

Mohamed Abdel-salam, Yang Gao

Abstract:	Troposphere and ionosphere play a crucial role in many disciplines such as wireless communications, aviation, and weather forecasting. Therefore, this paper deals with three atmospheric related subjects: absolute zenith troposphere delay (ZTD) estimation, absolute troposphere modeling using surface meteorological parameters, and absolute ionosphere delay estimation. Based on a developed precise point positioning system, the absolute troposphere delay is estimated. Then its wet component was calculated by modeling the dry part using surface meteorological parameters. The PPP’s ZTD is compared with the same product obtained from IGS, whereas the extracted absolute wet zenith troposphere delay is compared with Wet ZTD obtained from a Water Vapor profiler (WVP). The consistency between PPP’s ZTD and the other two methods is presented and analyzed. A consistency in the order of a few and several mm were obtained for the bias and standard deviation, respectively based on the exclusion of the first two hours of the PPP processing. The second subject of the paper addresses the accuracy of troposphere modeling in the existence of meteorological surface parameters. The results of this comparison show an agreement in the order of mm level when using several days of GPS data. The last subject tackled in this paper is a proposal for a new approach that is used for estimating absolute ionosphere delay based on un-differenced float ambiguities. A comparison between this method and the absolute ionosphere delay obtained from code observations is presented. The comparison includes an analytical and a numerical part. The results obtained from both methods show a bias of less than two decimeters.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	933 - 940
Cite this article:	Abdel-salam, Mohamed, Gao, Yang, "Improved Tropospheric Delay Estimation for Long Baseline, Carrier-Phase Differential GPS Positioning in a Coastal Environment," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 933-940.
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