Field Test of Trimble 4000 Real-Time Kinematic GPS Survey System

Abstract

The California Department of Transportation (CALTRANS) conducted a field test of the Trimble 4000 SSE Real-Time Kinematic (RTK) GPS survey system in February and June of 1996. The object of the test was to independently analyze the repeatability of the RTK survey system. During three days of observations, 156 station occupations were performed on a network of 10 stations. The results of the RTK testing were then compared against results from a static GPS survey of the network. Ellipsoid heights from the static survey were combined with the GEOID93 height model and compared against geodetic leveling as a further quality check. All RTK observations were limited to no more than 500 m in length. In these comparisons, RTK results demonstrated RMS errors of ±12.2 mm and ±22.6 mm for their respective horizontal and vertical components. Evidence is presented that suggests that vertical RTK accuracy may be affected by time-dependent systematic error.