Assessment of Factors Influencing Static GNSS Precise Point Positioning: A case study in Egypt

The Global Navigation Satellite Systems (GNSS) have been revolutionized in the last two decades in terms of precise results and wide utilizations in several engineering applications worldwide. Recently, the Precise Point Positioning (PPP) technique proves to enhance the GNSS accuracy while reducing projects' costs in terms of reducing the needed time and instruments for field data collection. This paper investigates some factors affecting the PPP solutions particularly in Egypt, through inspecting the effects of: (1) observation time, (2) precise versus broadcast satellite ephemerides, (3) single versus dual-frequency observations, (4) cut-off angle, and (5) GPS-only versus GPS+GLONASS GNSS. Three 24-hour GNSS datasets have been collected in the northern region of Egypt, and have been processed in several scenarios. It has been concluded that the utilization of precise satellite ephemerides, instead of the broadcasted ones, enhance the overall accuracy of the 3D coordinates by almost 71%. Additionally, It has been found that utilizing dual-frequency equipments produce accuracy improvements range from 60% to 84% in X,Y,Z coordinates. In addition, results show that the utilization of smaller cut-off angle in processing GNSS datasets could significantly enhance the attained result. Furthermore, it has been inferred that overall accuracy improvements due to using GPS+GLONASS datasets equal 20%, 23%, and 18% in the X, Y, Z coordinates respectively. Therefore, it is concluded that the presented PPP strategy has a crucial influence on surveying and geodetic activities in terms of accuracy and costs. It is, consequently, recommended that such strategy should be applied in high-precision geodetic applications in Egypt.