Comparison of GPS estimates of wet tropospheric delays with WVR measurements




Nam YS
Da K
Schutz BE

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Inst of Navigation, Alexandria, VA, USA


In March of 1995, a 5 day GPS campaign with Water Vapor Radiometer (WVR) and surface meteorological (SM) measurements was carried out at Eagle Point, located on Galveston Bay, and at the McDonald Observatory, near Fort Davis, Texas. GPS measurements from the experiment sites and two additional International GPS Service (IGS) stations (Pie Town, New Mexico and Richmond, Florida) were processed together using the TEXGAP software package developed at the University of Texas at Austin, Center for Space research (CSR). Tropospheric zenith wet delays at the experiment sites were estimated as an average value over one hour intervals while zenith hydrostatic delays were computed from SM data. During the processing, GPS orbits were fixed to the precise ephemerides determined by CSR and the coordinates of the McDonald site were fixed to the ITRF93 frame as fiducial. Comparison of the GPS estimated zenith wet delays with those from WVR over the 5 day period shows an RMS accuracy of about 7-8 mm, which is about 1 mm in precipitable water vapor (PWV). Daily accuracy of GPS estimates shows 6 mm (better than 1 mm in PWV) at McDonald. But when azimuthal variation of tropospheric wet delay is extremely high, there is less agreement between GPS estimates and the WVR measurements. Error sources for an observed bias difference between GPS estimates and WVR measurements were identified as GPS orbit errors (2-3 mm) and fiducial coordinates error (2 mm)




Computer simulation, Global positioning system, Meteorology, Parameter estimation, Radiometers, Texas, Troposphere, Water