Experimental Verification of Improved GPS-Measured Baseline Repeatability Using Water-Vapor Radiometer Corrections

We report a Global Positioning System (GPS) baseline measurement during which simultaneous water-vapor-radiometer (WVR) observations along the line of sight to NAVSTAR satellites were obtained. A single-wavelength GPS receiver (Macrometer¿ V-1000) and a WVR (developed by NOAA) were operated at each end of a 22km baseline near Boulder, Colorado, on three consecutive evenings in July 1983. The WVR´s were pointed toward each satellite sequentially at 15-min intervals during GPS data acquisition. The baseline vector was calculated using both a conventional correction for tropospheric water vapor and phase corrections derived from WVR data. Single-, double-, and triple-difference processing of the GPS data were carried out, without fixing phase ambiguities to integer values. WVR corrections improved the repeatability of the baseline vector, systematically shortening the vertical and east-west components.