Assessing GPS + Galileo Precise Point Positioning Capability for Integrated Water Vapor Estimation

Abstract

Although conventionally used for positioning, navigation, and timing, GNSS observations constitute a useful tool for atmospheric remote sensing. By quantifying and analyzing the influence of the atmosphere on the propagating electromagnetic signals, we can infer a significant amount of information for further understanding Earth’s atmosphere as well as its relationship with satellite positioning activities. For some industrial sectors that require high accuracy and reliability, such as oil exploration, dredging, and aviation, the understanding of how GNSS satellite signals propagate across the atmosphere is crucial information. Among several improvements related to GNSS, the increasing number of in-orbit Galileo satellites opens a new window of opportunities for atmospheric research. Users can achieve improved satellite geometry and take advantage of Galileo signal characteristics, such as improved signal strength. In this study, the usage of Galileo signals for neutral atmospheric delay (NAD) estimation is assessed along with its integration with signals from the already established GPS constellation. Using the University of New Brunswick’s GNSS Analysis and Positioning Software (GAPS) precise point positioning suite, the NAD values are estimated and integrated with in situ measurements of pressure, temperature, and humidity, allowing us to estimate the integrated water vapor (IWV) of the atmosphere above a GNSS station. As a reference for the estimation assessment, existing IWV values from radiosondes are used. Preliminary results show that the Galileo + GPS NAD estimations are close to those of GPS at the 2-centimeter level. The recently-released multi-GNSS processing online version of GAPS is now able to provide users with a useful tool for atmospheric research.