Research And Realization On GPS Multi-Antenna Deformation Monitoring System

GPS is widely used in deformation monitoring for the dam, the bridge and the tall building because of high accuracy, round-the-clock and automation. But the high cost of the traditional deformation monitoring system limits the application and extension. Aiming at the problem, the GPS multi-antenna microwave switch which possesses the national patent is developed and the GPS multi-antenna deformation monitoring system is designed. The system can monitor several points with one GPS receiver. So it reduces the cost greatly. At the same time, the accuracy is not decreased.This paper first introduced the basic theories of the GPS defomation system including the measuring principles of the carrier phase of GPS, the error sources and elimination in GPS measurement, the property of combined dual frequency carrier phase observation, the coordinate transformation between WGS-84 system and site-centric coordinate system, the basic model for the acquisition of deformation.The principle prototype of the GPS multi-antenna deformation system was designed using the microwave switch. The software of data acquisition and control system was developed using the Visual C++ 6.0 to realize the functions: control of multi-antenna microwave switch, communication with GPS receiver and PC104, conversion from GPS raw data to standard RINEX2.10 format.Single epoch algorithm for the GPS deformation monitoring information based on the combination of carrier phase was put forward for dynamic monitoring. The problems of"detection and repair of cycle slips"and"determination of ambiguity"can be avoided. The deformation information under 0.8 meter could be calculated and the accuracy could be improved by the precise processing.A lot of experiments using the principle prototype indicate that the microwave switch has almost no influence on the snr of GPS and the measurement accuracy of baseline and deformation information.