Detecting Errors in GNSS-Precise Point Positioning Controls Using Total Station Technique

Abstract

Global Navigational Satellite System-Precise Point Positioning (GNSS-PPP), is a type of GNSS technique that uses one receiver to acquire satellite signal to fix position. GNSS-PPP is not free from error just as any other measurement in surveying and the Total Station instrument could be used to detect such errors. The aim of this study was to detect errors in Precise Point Positioning (PPP) Controls using Total Station survey. Hi-Target GNSS receiver was used to acquire raw satellite data that were used to fix the selected control points at duration of 60 minutes on each point. The raw satellite data were converted to RINEX data which would be readable by the post processing software. The RINEX data were uploaded to online post-processing solution where they were processed and the results were sent back. After that, the Total Station instrument was used to run a Survey on coordinate mode on all the initially selected control point for GNSS-PPP. The Total Station survey was carried out two times on separate days to determine the average of the results. Comparison of the results of average of the Total Station and that of GNSS-PPP were made and their differences were in decimetre range except for three controls that are in meter range.  Further investigation shows that the three controls that had their results in meter range were so close to power lines, communication mast and storey buildings. These contributed to interferences and obstructions to the signal of the satellites, thereby creating multipath errors on those control points. It was therefore recommended that the Total Station be used wherever there are perceived interference to clear sky satellite in order to achieve high accuracies with GNSS-PPP measurements.