Real-time integrated water vapor determination using OTF carrier-phase ambiguity resolution in WADGPS networks

M. Hernández-Pajares, J. M. Juan, J. Sanz, O.L.Colombo and H. van der Marel

Abstract:	A major issue in many applications of GPS is the real-time estimation of the Integrated Water Vapor (IWV). Several authors have developed strategies that estimate IWV, or equivalently Zenith Tropospheric Delays (ZTD), with a latency of one hour or more. These strategies require that data from a regional GPS network be processed in near real-time, using precise IGS orbits in combination with partial orbit relaxation. It has been shown recently that in Wide Area Differential GPS (WADGPS) networks several hundred Km across, double-differenced carrier phase ambiguities can be computed on-the-fly, using a real-time tomographic model of the ionosphere obtained from the same GPS data. In this work we study how such ambiguity resolution can help determine in real-time, instantaneously, the ZTD for a WADGPS network, using only the broadcast ephemeris. This approach allows any user in the WADGPS area to easily get its own real-time precise ZTD determination, which can be converted to IWV using measurements of atmospheric pressure. The comparison between the real-time strategy presented and the postprocessed approach shows a general agreement of about 1 cm in the ZTD in WADGPS scenarios, improving by about 30-40% the results obtained also in real-time but without fixing the carrier phase ambiguities, for both reference and rover receivers. These results are achieved or can be achieved not only in quiet ionospheric conditions, but also during ionospheric disturbances and Solar Maximum conditions. This is an important issue for the ionospheric modeling, which is a key element of the algorithm. In coming years, data from ground and satellite-borne GPS receivers will help monitor the state of the atmosphere (mapping tropospheric IWV and ionospheric TEC), to study weather, Earth-sun interactions, and climate change. Real-time ambiguity resolution can enhance not only present uses of wide area GPS networks, in navigation and surveying, but also creates new ones in the field of meteorology.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	616 - 625
Cite this article:	Hernández-Pajares, M., Juan, J. M., Sanz, J., O.L.Colombo,, Marel, H. van der, "Real-time integrated water vapor determination using OTF carrier-phase ambiguity resolution in WADGPS networks," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 616-625.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In