RTK GPS - quality in the field

摘要

Real-time kinematic (RTK) GPS is more and more taking over traditional surveying tools. In 2000, the Finnish Geodetic Institute performed a study to investigate the quality of RTK GPS and get an overview of the factors that affect RTK measurements. Measurements were done at two test fields in rural areas with equipment from five different manufactures. The accuracy values specified by the manufacturers are under good conditions: 10 mm + 1-2 ppm for plane coordinates and 15-20 mm + 2 ppm in height. The test results showed that these values can also be met under less favourable circumstances. However, the surroundings of the measured points proved to have a big influence on the accuracy of the measurements. No clear correlation was found between the PDOP values and the measurement accuracy. But, with increasing number of satellites the average initialisation time became shorter and the repeatability of the solution got better. Regarding reliability of the system, comparison of the measurement results with the accuracy values predicted by the RTK equipment showed that the equipment predicts the expected measurement accuracy quite well. Some big measurement errors, however, could not be detected by looking at the predicted accuracy values alone. The tests showed that these errors could be detected by independently repeating the measurements.