PPP and Network True Real-time 30 sec Estimation of ZTD in Dense and Giant Regional GPS Network and the Application of ZTD for Nowcasting of Heavy Rainfall

摘要

We have developed a true real-time ZTD processing system for GEONET (GPS Earth Observation NETwork) in Japan by using both precise point positioning (PPP) and network double-differential processing, where "true" means ZTD product availability within several seconds of GPS observations. The two processing systems are designed for potential users who need true real-time GPS tropospheric products for weather forecasts and nowcasting by monitoring current precipitable water vapor (PWV) for short-term prediction of severe rainfall. The PPP processing system first estimates satellite clocks based on zero-differenced observation in a network processing with 23 stations, and the estimated satellite clocks are used for PPP processing for more than 1,300 stations. The network processing system consists of 61 networks where each network has more than 20 stations