IAG | 2021-04-20

SG 1.2.1: Relevance of PSInSAR analyses at ITRF co-location sites

Relevance of PSInSAR analyses at ITRF co-location sites

Chair: Xavier Collilieux (ENSG, France)

Vice-Chair: Thomas Fuhrmann (Geoscience Australia)


Terms of Reference

The scientific community has recognized the need for a highly accurate terrestrial reference frame (TRF) for Earth Science applications. Current determination of the International Terrestrial Reference System is made by combining data from space geodetic techniques, namely Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), Doppler Orbitography and Radiopositioning Integrated by satellite (DORIS), Global Navigation Satellite Systems (GNSS), but also terrestrial measurements from local tie survey at co-location sites. For most of the sites, such local tie surveys are not performed on a regular basis. Thus, it is not possible to test the assumption of no relative motion between instrument reference points which is currently done almost exclusively by analyzing space geodetic data themselves.


The PSInSAR (Persistent Scatterer Interferometric Synthetic Aperture Radar) technique allows for determining deformation maps over large areas with various spatial resolutions as function of the satellite missions. Due to the availability of freely available SAR data for a significant period of time at many sites, it is relevant to ask if such data could supplement local tie measurements for those sites where sufficiently repeated terrestrial surveys do not exist. There are however some limitations that need to be addressed such as the size of a co-location site which is between 100 m and 1 km or the reference points themselves that are not accessible from the SAR satellites. Artificial corner reflectors or active transponders might however be used to add a PSInSAR measurement point in this context. Studying PSInSAR results in C- and X-band at some co-location sites is worth investigating to assess the potential use of this technique in reference frame determination in the future.



The main objective is to investigate if the PSInSAR technique can be used to supplement local tie surveys at ITRF multi-technique sites.


Proposed activities

·         List strength and weakness of the PSInSAR technique for this application.

·         Collect all studies related to INSAR and more particularly PSInSAR at co-location sites.

·         If relevant, make an inventory of SAR images (for all missions) available at ITRF co-location sites.

·         If relevant, identify multi-technique co-location sites where PSInSAR processing should be performed and compare InSAR results from various software packages.

·         Compare results of free, but low-resolution, Sentinel-1 data with commercial high-resolution data (e.g. TerraSAR-X) where available; investigate whether a request for a supersite could be used to obtain additional high-resolution data (see https://www.earthobservations.org/documents/gsnl/20120918_GSNL_CEOSSelectionProcess.pdf).  

·         Investigate the relevance of installing corner reflectors or transponders at co-location sites.

·         Report conclusions and recommendations in IAG 2021 and/or IUGG2023 proceedings.


List of members


-                  Xavier Collilieux (ENSG Paris, France)

-                  Thomas Fuhrmann (Geoscience Australia, Australia)

-                  Stefan Friedländer (BKG, Germany)

-                  Thomas Gruber (TU Munich, Germany)

-                  Clément Courde (CNRS, France)

-                  Christoph Gisinger (DLR, Germany)

-                  Francesco DeZan (DLR, Germany)

-                  Amy Parker (Curtin University/CSIRO Australia)

-                  Munekane Hiroshi (GSI Japan, Japan)


Corresponding members

-                  Ann Chen (UT Austin, USA)

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