The first PPP-based GPS water vapor real-time monitoring system in Pearl-River-Delta Region, China

The first Precipitable Water Vapor Real-Time Monitoring System (PWVRMS) based on Global Positioning System Precise Point Positioning (PPP) technique has been developed for the Pearl-River-Delta region. This PWVRMS system estimates GPS satellite clock error data in real-time while using International GNSS Service (IGS) predicted precise satellite orbit directly. Currently it processes GPS data every 10 min on a daily basis from three networks in Pearl-River-Delta region: Hong Kong SatRef GPS network, Macao MoSRef GPS network and Guangdong CORS network. Compared to traditional double-differencing technique, the advantage of using PPP technique is that (1) the PWV estimation at each station is completely independent and is not affected by data quality at other stations; (2) the computation is much faster and simpler. This PWVRMS system is evaluated using radiosonde water vapor data. The GPS PWV accuracy is about 2.20 mm though the GPS station is 4.1 km away from the radiosonde. It is expected the actual GPS PWV accuracy should be higher if the GPS station is collocated with the radiosonde station. The real-time PWV products can be widely used in weather forecasts, climate researches, and water vapor correction for remote sensing images such as SAR applications. Currently the PWVRMS supplies real-time water vapor data to several meteorological agencies in Pearl-River-Delta region including Hong Kong Observatory, Macao Meteorological and Geophysical Bureau, Shenzhen Meteorological Bureau and Guangdong Meteorological Bureau for their weather forecasting service and research.