Examining PPP accuracy in relation to altitude

Abstract

Online PPP services are increasing daily due to their user-friendly interfaces, quick turnaround times, the ability to evaluate data from a single GNSS receiver, and their cost-free nature. However, the veracity of the data provided by these services needs to be verified. This study examined the position and height accuracy variation provided by PPP services based on benchmark point altitudes. For this purpose, seven measurement points were established every 200 meters, starting from the sea level. Four-hour static GNSS observations were carried out at each point, and these data were first evaluated with the static post-processing method to obtain the known positions of the points. The static observations were then submitted to the popular online PPP services Trimble-RTX, AUSPOS, and CSRS-PPP, and the received position and height data were compared to the point’s known coordinates. When the results were analyzed, it was found that changes in the position data were in the order of cm, while changes in the height data were in the order of 1-2 dm, depending on the altitude of the measurement point.