Motion Detection with GPS

Abstract: Using GPS technology in motion detection and deformation measurements are getting more common. Different concepts are used; GPS as a stand-alone system or together with other surveying methods. A lot of research is done in this field and several types of applications have been developed. In this work only GPS receivers are used and the focus is on centimetre level motions over short periods of time. Because the created horizontal motion is known the accuracy of the by GPS detected motion can be computed for different settings and in different environments. A brief overview of the limitations and error sources in GPS surveying is also given.The motions are monitored with a commercial software, Motion Tracker, from Trimble and with On-the-Fly processed data files from Trimble Total Control that are run in a Matlab program in order to get RMS values for the detected motions and plots showing the created true motion and the by GPS measured motion. In addition the procedure to write a batch file in order to run GNNET-RTK, a software from GEO++, is investigated. This software package makes it possible to simultaneously do real-time processing of several reference and rover stations.When the conditions for GPS surveying are good, the quality of detected motions show promising results. Millimetre accuracy is achieved even if only GPS sensors are used and the epochs are as short as one minute. In built up areas with a lot of obstructions of the sky the error sources and limitations of GPS, e.g. multipath, has a significant impact on the results and longer observation times are needed. In such areas this work indicates that for demanding high accuracy applications GPS needs other types of sensors as complement, to be able to provide stable reliable solutions with millimetre accuracy.