Site-Dependent Electromagnetic Effects in High-Accuracy Applications of GNSS (original) (raw)

Agu Fall Meeting Abstracts, 2008

Abstract

Global Navigation Satellite Systems, GNSS are used in many applications demanding millimetre-level accuracy in positioning. Such applications include monitoring of crustal movements. The GNSS technique also facilitates estimates of the tropospheric water vapour content, an important parameter in numerical weather predictions and climate research. The accuracy of estimated parameters is however degraded by many error sources. Some of those are related to the satellite system and the ground-based receivers. During 2006 the International GNSS Service, IGS implemented absolute antenna calibration for both satellite antennas and the different antenna types used at the ground-based stations. The use of such calibration values improves the accuracy as antenna type related errors are mitigated. However, unmodeled error sources still remain since a antenna couples electromagnetically with its surrounding environment. The absolute antenna calibrations, to be implemented by the IGS, will however not compensate for site- dependent effects. To further improve the accuracy, the site-dependent effects and their dependency on the direction of the observation need to be identified and removed in the GNSS data analysis. In this presentation the site-dependent error sources have been studied for the stations in the Swedish permanent GNSS network, SWEPOS, as well as some stations in the global IGS network. Strong similarities in terms of site-dependent effects were found. Differences in the site characteristics, caused by multipath and different antenna surroundings imply that an individual calibration of each station may be required needed. We have developed and evaluated two different methods for calibration of site dependent effects.

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