The application of GPS in shanghai land subsidence research

Shanghai launched the research of monitoring the land subsidence with GPS since 1998,which includes the demonstration of monitoring land subsidence with GPS,the construction of GPS fiducial network,GPS Data processing and network adjustment etc.Also,the GPS fiducial network making up of 34 sites which almost cover the whole shanghai region was constructed.On the other hand,to improve the precision of the GPS fiducial network and the spatio-temporal resolution of Shanghai land subsidence monitoring,four GPS Continuously Operating Reference Stations(CORS) have been constructed on 2004.Here,based on the work accomplished,we introduce and summarize the experience obtained.What's more,to examine what precision of ellipsoid height can be achieved,get the reasonable observation program and the best scheme of GPS Data processing,we analyzed six groups of GPS data observed since 1998 with software GAMIT/GLOBK and GPS_NET.Results indicate that the precision of WGS-84 ellipsoid height can be best as 2mm even the baseline's length is up to 30~40km.This order of precision can be used to separate the subsidence more than 3mm,which can perfectly meet the need of Shanghai land subsidence monitoring.