A new strategy for real-time integrated water vapor determination in WADGPS networks

Abstract. A major issue in many applications of GPS is the real-time estimation of the Zenith Tropospheric Delays (ZTD). Several authors have developed strategies that es-timate ZTD, with a latency of one hour or more in or-der to compute Integrated Water Vapor (IWV), using lo-cal measurements of surface pressure, or to assimilate ZTD into Numerical Weather Predicition (NWP) models. These strategies require that data from a regional GPS network be processed in near real-time, using precise IGS orbits and partial orbit relaxation. Recently it has been shown that in Wide Area Dierential GPS (WADGPS) networks of several hundred kilometers across, double-dierenced carrier phase ambiguities can be computed on-the-fly, using a real-time to-mographic model of the ionosphere obtained from the same GPS data. In this work we show how ambiguity resolution can help determine in real-time the ZTD for a WADGPS network user, only 10-20 % worse than those of the post-processed solutions. 1