Geolocation accuracy and precision for InSAR point positioning; validation using the Dutch IGRS network

Precise and accurate geolocation of (point) scatterers is crucial for the correct interpretation of InSAR time series in the built environment, since this allows the scatterers to be linked to physical objects. The precision and accuracy of the geolocation is dependent on orbit precision, sub-pixel scatterer localization within the SAR images, as well as a range of geophysical, SAR processor, and instrument-related corrections.

 

Focusing on the abundantly available Sentinel-1 SAR acquisitions, previous studies on 40 corner reflectors in  Australia, with 30 acquisitions aligned towards ascending orbits (Garthwaite et al., 2015), and georeferenced using annual GNSS campaigns, yielded a positioning dispersion (1sigma) of 6~cm in range and 26~cm in azimuth, and residual offsets of 3~cm (range) and 18~cm (azimuth) (Gisinger et al., 2021).  

 

Here we report on new results applied on the network of Integrated Geodetic Reference Stations (IGRS) in the Netherlands, which currently consists of 80 corner reflectors on 40 stations (i.e., ascending and descending) on the same physical construction, equipped with permanent GNSS stations.   The already developed end-to-end methodology for SAR geolocation is revised, and applied to Sentinel-1 interferometric wide swath (IW) data from 257 ascending and 263 descending acquisitions.  Our results confirm the validity of the applied corrections.