Developing a method for reducing GPS occupation times

SUMMARY Developing a Method for Reducing GFS Occupation times Use of GPS in deformation monitoring is rapidly increasing due to its high accuracy and handling three dimensional coordinates at the same time. But using standard GPS methods in deformation monitoring is not economical because of its requirement of a long period of field measurement time. Especially, continuity or periodicity in measurements effects staying time at the field and economy at the negative way. In this research, a method and software are developed in order to reduce field measurement time to minumum and getting maximum accuracy which can be achived from GPS. On this method, double difference GPS phase measurements are used. Focus of research is determination of N (Integer phase ambiguities) which is the most effective factor causes field measurements longer. N can be determined using coordinates of the points which are measured standard GPS or terresterial methods. The starting point of this research is these known coordinates. At the subsequent measurements, point cordinates will be determined by developed method and software which is running Quick C environment in PC's. In this research, period of measuring of a baseline is reduced to level of several minutes. This method can be used for networks whose baselines shorter than 10 km. In order to test methodology and developed software, a network with four point are processed. Testing results showed that using Bernese software and whole of the observations (about 2-3 hours) determined coordinates are reached an agreement of level of millimeter with using the developed method and software with 2-3 minutes observations of all. Key Words: GPS (Global Positioning System), Deformation monitoring, N (Integer phase ambiguities). VIII