Geodetic SAR for Height System Unification and Sea Level Research—Results in the Baltic Sea Test Network

Thomas Gruber*, Jonas Ågren, Detlef Angermann, Artu Ellmann, Andreas Engfeldt, Christoph Gisinger, Leszek Jaworski, Tomasz Kur, Simo Marila, Jolanta Nastula, Faramarz Nilfouroushan, Maaria Nordman, Markku Poutanen, Timo Saari, Marius Schlaak, Anna Świątek, Sander Varbla, Ryszard Zdunek

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Coastal sea level is observed at tide gauge stations, which usually also serve as height reference stations for national networks. One of the main issues with using tide gauge data for sea level research is that only a few stations are connected to permanent GNSS stations needed to correct for vertical land motion. As a new observation technique, absolute positioning by SAR using off the shelf active radar transponders can be installed instead. SAR data for the year 2020 are collected at 12 stations in the Baltic Sea area, which are co-located to tide gauges or permanent GNSS stations. From the SAR data, 3D coordinates are estimated and jointly analyzed with GNSS data, tide gauge records and regional geoid height estimates. The obtained results are promising but also exhibit some problems related to the electronic transponders and their performance. At co-located GNSS stations, the estimated ellipsoidal heights agree in a range between about 2 and 50 cm for both observation systems. From the results, it can be identified that, most likely, variable systematic electronic instrument delays are the main reason, and that each transponder instrument needs to be calibrated individually. Nevertheless, the project provides a valuable data set, which offers the pos-sibility of enhancing methods and procedures in order to develop a geodetic SAR positioning technique towards operability.

Original languageEnglish
Article number3250
Number of pages33
JournalRemote Sensing
Issue number14
Publication statusPublished - 1 Jul 2022
MoE publication typeA1 Journal article-refereed


  • geodetic SAR positioning
  • geoid
  • GNSS
  • GOCE
  • height system unification
  • sea level
  • Sentinel-1
  • tide gauge


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