Abstract
Abstract Radar Corner Reflectors (CR) are increasingly used as reference targets for land surface deformation measurements with the Interferometric Synthetic Aperture Radar (InSAR) technique. When co-located with ground-based Global Navigation Satellite Systems (GNSS) infrastructure, InSAR observations at CR can be used to integrate relative measurements of surface deformation into absolute reference frames defined by GNSS. However, CR are also a potential source of GNSS multipath effects and may therefore have a detrimental effect on the GNSS observations. In this study, we compare daily GNSS coordinate time series and 30-second signal-to-noise ratio (SNR) observations for periods before and after CR deployment at a GNSS site. We find that neither the site coordinates nor the SNR values are significantly affected by the CR deployment, with average changes being within 0.1 mm for site coordinates and within 1 % for SNR values. Furthermore, we generate empirical site models by spatially stacking GNSS observation residuals to visualise and compare the spatial pattern in the surroundings of GNSS sites. The resulting stacking maps indicate oscillating patterns at elevation angles above 60 degrees which can be attributed to the CR deployed at the analysed sites. The effect depends on the GNSS antenna used at a site with the magnitude of multipath patterns being around three times smaller for a high-quality choke ring antenna compared to a ground plane antenna without choke rings. In general, the CR-induced multipath is small compared to multipath effects at other GNSS sites located in a different environment (e. g. mounted on a building).
Highlights
Interferometric synthetic aperture radar (InSAR) technology has been widely applied to measure and map the Earth’s land surface deformation arising from natural or anthropogenic phenomena [1, 2, 3]
We find that neither the site coordinates nor the signal-to-noise ratio (SNR) values are significantly affected by the Corner Reflectors (CR) deployment, with average changes being within 0.1 mm for site coordinates and within 1 % for SNR values
The potentially detrimental effect that the presence of CR co-located at Global Navigation Satellite Systems (GNSS) sites has on the GNSS signal is an understandable concern for GNSS network operators
Summary
Interferometric synthetic aperture radar (InSAR) technology has been widely applied to measure and map the Earth’s land surface deformation arising from natural or anthropogenic phenomena [1, 2, 3]. In order to make precise comparisons between InSAR and other geodetic measurement techniques and to fully integrate InSAR into geodetic reference frames, a network of ground-based artificial radar targets can be deployed [5]. Such radar targets provide a high-quality, temporally stable phase response in SAR imagery, which is required for reliable time series analysis of InSAR phase measurements to derive surface deformation [6]. There are concerns about degrading GNSS signals when co-locating CR at continuously op-
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