Evaluation of Kinematics GNSS PPP for Tropospheric Zenith Wet Delay Estimation in Mountainous Regions

In this research, the effectiveness of kinematic zenith wet delay (ZWD) estimation using global navigation satellite systems (GNSS) precise point positioning (PPP) techniques is evaluated. The major challenges of kinematic ZWD estimation compared to static mode are (1) significant and variable GNSS signal obstruction, (2) trajectory durations of several hours compared to several days in static mode and (3) strong correlation between ZWD and height estimates. High-end and low-cost receivers are tested on vehicular highway trajectories through mountainous regions with height changes over 1000 m and varying levels of GNSS obstruction. Results are compared to static tests with open-sky conditions.

Static agreement of ZWD profiles of high-end receivers was found to be at the sub-millimetre level. Agreement of low-cost receivers when using a high-grade antenna was found to be at the level of 3 mm or better. Low-cost receivers using low-cost antennas suffered ZWD biases of 3 cm due to height biases of 7-10 cm. Kinematic accuracy of ZWD profiles for high-end receivers in trajectories with minimal obstruction was found to be 5 mm, increasing to 10 mm in trajectories with more obstruction and 25 mm in very harsh obstructions. Accuracy of ZWD profiles for low-end receivers ranged from 8-20 mm in open conditions and 20-35 mm in more challenging conditions. Low-cost receivers were not tested in very harsh obstructions. Empirical ZWD models were found to agree with high-end receiver PPP-derived ZWD profiles within 15 mm or better, hence accuracy poorer than 15 mm appears ineffective.