Evaluation of Positioning Accuracy in Real Time Differential GPS

The positioning accuracy of differential global positioning system (DGPS) by the method of pseudo range correction is reported in this paper. Evaluation test of DGPS was conducted in Tateyama Bay using an observation vessel in mooring, drifting and cruising conditions. The pseudo range correction value and the change rate, which were measured at a DGPS reference station set in the fixed point of Yokohama aparted about 7OKm from Tateyama, were transmitted continuosly to a user GPS receiver installed on the observation vessel through a wireless telephone link in real time. The positioning accuracy of DGPS throughout the examination period was very high and stable as compared with uncorrected GPS positions which vary largely and irregularly with time. The positioning error was 1.3m in terms of standard deviation. The efficiency of real time DGPS as a precise positioning system at sea, was confirmed from this experiment results.