IGS point positioning accuracy on IGS network scales

As the GPS came into the surveying engineering, a lot of studies have been done in the fields of the precision of point positioning. It is really important for surveying engineers, to determine the precision of point location in the level of mm. Technically, the observation window (or data span) plays an important role to determine the point position sufficiently well. While, over short baselines, as one tries to determine the point location, it is possible to reach the desired precision by making the receiver stay on the point for few hours. It is an uncertain topic that precision is dependent on baselines for longer baselines (Eckl vd. 2001, Dogan 2007). In this study, GPS point positioning accuracy is tested in IGS network and the results are compared with recent researches by using GIPSY software. 7 bases and data of 10 days have been used in this research. Base lengths are between 295km and 2739km. The data of each day have been divided into sub sessions (4-6-8-12 and 24 hours) and then evaluated separately. Thus, relation have been examined among GPS point positioning, baseline and duration of observation. The results show that, the point positioning accuracy in IGS network does not depend on baseline up to 2000 km. It is rather depend on duration of observation. Keywords: GPS point positioning precision, IGS datas, observation window, baseline.