Comparative analysis of the performance of Multi-GNSS RTK: A case study in Turkey

The Real Time Kinematic (RTK) method is widely used in the land surveying. Whereas RTK method has the advantage of practical use, positioning accuracy depends mostly on the baseline length due to the atmospheric errors. In general, RTK measurements are made by using GPS and GLONASS satellite systems. For this reason, the positioning performance of the technique is adversely affected under restricted satellite geometry conditions such as urban canyons. At present, most receivers on the market have the ability to track signals of Galileo and BeiDou satellites. Therefore, in this study, the positioning performance of RTK with different satellite combinations (GPS-only, GPS+GLONASS, GPS+GLONASS+GALILEO+BeiDou) was examined with a comparative approach. A field test was carried out considering approximately 20, 40, 60, and 80 km length of baselines. Three different cut off elevation angles - namely, 10 degrees, 20 degrees, and 30 degrees - were chosen for the field test. The results were investigated in terms of accuracy and precision. Also, the ground truth coordinates of the rovers were obtained by post-processing relative method using GAMIT/GLOBK software. The results showed that multi-GNSS combinations provided better repeatability at the 10 degrees cut off angle option. The accuracy of GPS-only solutions varied between 0.63/2.17 cm and 2.40/4.94 cm for horizontal and vertical components, respectively. However, the multi-GNSS combinations did not have a remarkable superiority in terms of position accuracy even at high satellite cut off angle (30 degrees) compared to the GPS-only RTK.