This study deals with the performance of the multi-GNSS positioning techniques, such as standard point positioning (SPP) and post-processed kinematic (PPK). To this end, the real-world data sets obtained by continuously operating reference stations (CORS) in Korea have been processed with a consideration of the different operational environments by setting variant cut-off angles. Results of the processing and analysis can be summarized as belows:
(a) The accuracy of GPS’s SPP at the begin environment (i.e., 15°of cut-off angle) has been evaluated to be ±2.7m and ±6.5m in the horizontal and vertical component with 95% confidence level. Although the GPS/Galileo positioning scenario slightly enhanced the accuracy at the same positioning condition. The inclusion of the GLONASS and BeiDou measurements adversely impacted into the accuracy. Especially, when the BeiDou was integrated to the other systems, the error of the ellipsoidal height was increased. The result was mainly due to the factor that signal in space ranging error (SISRE) of GLONASS and BeiDou satellites are relatively larger than those of GPS and Galileo.
(b) According to the increase of the cut-off angles, the availability of the GPS stand-alone SPP was got worse down to 30% if the angle was set to be 45°. On the other hand, if the multi-GNSS positioning scenarios were considered, the availability became significantly improved to 100% by integration of GPS with one and two more constellations for 30° and 45°of the cut-off angles.
(c) The accuracy of GPS’s PPK positioning with the 15°of the cut-off angle was assessed to be ±2.5cm and ±3.8cm with the 95% confidence interval in the horizontal and the vertical component. The integer ambiguity was resolved for all the epochs. Contrary to the SPP results, the PPK accuracy of the multi-GNSS positioning has been increased in that the differencing technique was applied to correct not only the SISRE but also the signal propagation and the receiver-dependent errors. It is worth taking note that the observations obtained by the same types of GNSS receivers were processed in this research.
(d) Results of the PPK positioning with the 30°of the cut-off angle reveals that the accuracy and the availability of GPS stand-alone case were decreased with the limited number of the available satellite measurements. For instance, 75% of the processing epochs were solved with the fixed ambiguity. As expected, employment of the multi-GNSS observations increases the accuracy and the availability with the enhanced performance of the ambiguity resolution. The ambiguity successful rate of the two GNSS integration was about 98% whereas those of three constellations was 100%.