POINTED WATER-VAPOR RADIOMETER CORRECTIONS FOR ACCURATE GLOBAL POSITIONING SYSTEM SURVEYING

Delay of the Global Positioning System (GPS) signal due to atmospheric water vapor is a major source of error in GPS surveying. Improved ver tical accuracy is important for sea level and polar isostasy measureme nts, geodesy, normal fault motion, subsidence, earthquake studies, air and ground-based gravimetry, ice dynamics, and volcanology. We conduc ted a GPS survey using water vapor radiometers (WVRs) pointed toward G PS satellites to correct for azimuthal variations in water vapor. We r eport 2.6 mm vertical precision on a 50-km baseline for 19 solution da ys. Kalman filter or least-square corrections to the same data do not account for azimuthal distribution of water vapor and are degraded by 70%.