Accuracies of Position Fixes Obtained by GPS―II Simultaneous Observation at Two Fixed Stations

Simultaneous measurements were taken at two fixed stations in Nagasaki in order to evaluate the positioning accuracy of GPS for ten days in Jan., 1987. We received positioning signals from 6 satellites. The usable time at these stations was about 4.5 hours, 2 hours less than for the results reported in our previous paper. Two and three dimensional high level positioning accounted for 13～14% of the total time, i. e. about 40 minutes. The positioning errors at Nagasaki University agreed with the results of our previous reseach. Even the positioning error of 2L (two-dimensional low level positioning), which was largest, was only about 167 meters. The positioning errors at Nagasaki maru were large, and the largest positioning error of 2L was about 281 meters. As the data for high level positioning were few, we could not compare it in full with the positioning accuracy of combinations of satellites. Though the two fixed stations were quite near (about 9 kilometers), the combination of satellites or the number of satellites on positioning varied from observation to observation. The displacement of the two fixed stations on positioning at the same time varied from moment to moment and there were many cases in which the direction or the distance of the displacement did not agree