Research Of Monitoring Land Subsidence By GPS Surveying In Tianjin

The land subsidence is serious in our country especially in Tianjin. It isinfluencing our lives and productions badly. The principle and causation of the landsubsidence must be studied earnestly. It has become an earnest problem to foundsome reasonable measures to control the land subsidence. The scientific monitoringmethod of the land subsidence is very important in this task. In recent years, theapplication of GPS(global positioning system) in the monitoring of the landsubsidence became a focus in the academe.Based on the views mentioned above, the geologic and man-made causations ofthe land subsidence are carried out through analyzing the history and actuality of theland subsidence in Tianjin. The development, framework and elements of GPS arepresented in this dissertation. The principles of static and kinematic differentialglobal positioning system are discussed in detail. Resulting from the study on therelationship of positive altitude, geometrical height and the land subsidence, thecoherence of the monitoring land subsidence by GPS and precise leveling isapproved in theory. An example of monitoring Tianjin land subsidence by GPS isgiven. Through analyzing the precision and coherence of the monitoring results byGPS and precise leveling, it is shown that static DGPS can take the place of preciseleveling for monitoring large-scale land subsidence.The precision of RTK(Real Time Kinematic) monitoring is investigated in thisdissertation. The precision of RTK and second-class precise leveling is contrastedthrough analyzing the experimentation on the spot. The precision influenced by timeand distance is investigated in detail. It is shown that RTK monitoring can take theplace of second-class precise leveling in some special conditions.