Evaluating the Performance of the Static PPP-AR in a Forest Environment

Abstract

Forest environment and topographic obstacles tend to reduce the positioning performance of precise point positioning (PPP) with ambiguity resolution (AR) and may even prevent radio signals from reaching the global navigation satellite systems (GNSS) antenna. In this study, we investigated the positioning performance of PPP-AR in a forest environment in terms of the crown closure ratios, session duration (1-, 2-, 3-, and 6-h), and different satellite constellations [i.e., the global positioning system (GPS)-only and GPS+GLONASS combined satellites]. For this purpose, three GNSS receivers were used to make measurements at three test points in areas with crown closure ratios of 0%, 38%, and 87%. The data were evaluated using the PRIDE PPP-AR software and Canadian Spatial Reference System-PPP (CSRS-PPP). The experiments revealed that the inclusion of the GLONASS observations in the GPS-only solutions did not obviously improve the positioning error and accuracy with closure ratios of 0% and 38%. However, the improvements became more dramatic when the closure ratio increased to 87%. Furthermore, in the horizontal components, an accuracy of 10 cm can be achieved with at least a 2-h session, whereas for the up component, this level of accuracy can only be achieved with a 3-h session. While the PRIDE PPP-AR was able to achieve a 3D positioning performance of 1 cm with the combined GPS+GLONASS satellites, this accuracy level remained at 8 cm in CSRS-PPP.