Evaluation of atmospheric pressure loading effects on GPS

Abstract

As atmospheric pressure varies over time it exerts a dynamic load on the Earth, causing crustal deformations. When performing high precision GPS measurements, such deformations may affect the accuracy of the measurements. This Master of Science thesis aims at describing how atmospheric pressure loading tends to affect precise point positioning with GPS measurements and evaluate the effects. Furthermore, the goal of the longterm work, of which this evaluation is part, is to implement correction terms for crustal movements derived from atmospheric pressure loading in the GPS data processing software package GIPSY-OASIS and to perform tests to investigate the results on precise positioning. Deformation time-series data, based on 6-hourly NCEP reanalysis pressure data in a 2.5° x 2.5° grid, is downloaded from a database administrated by the VLBI group at NASA Goddard Space Flight Center. Subsequently, the deformation data is applied on GPS measurement data as daily average values and the results are analyzed. Results from comparing GPS displacement time series data with and without having applied the model for atmospheric pressure loading, respectively, show a reduced daily scatter at most of the investigated sites, especially for the radial component, after implementation of the model. This suggests that implementing terms of atmospheric pressure loading can enhance the accuracy in GPS measurements.