Sayung is a subdistrict in Demak Regency which is located on the north coast is very vulnerable to natural disasters such as rob flood, abrasion and deformation of land subsidence. The condition is suspected, among others, by several factors, among others, geological structure as a large area dominated by young alluvium layers are still experiencing compression, loading and retrieval of ground water. It is necessary to do research related to ground deformation. The geodetic method used for monitoring ground deformation by satellite surveys with GNSS. The research was conducted to observe GPS survey in 2015 and 2016. GNSS data would be processed with scientific processing GAMIT 10.6. Strategic of GPS data proccesing is the important to reach a better accuracy. The purpose of this research is to evaluate the result of calculation of coordinate value and spatial deformation obtained by both base station that is CORS UDIP and CORS CSEM for monitoring ground deformation.