{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,21]],"date-time":"2026-03-21T20:06:19Z","timestamp":1774123579431,"version":"3.50.1"},"reference-count":31,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2022,7,6]],"date-time":"2022-07-06T00:00:00Z","timestamp":1657065600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"European Space Agency (ESA)","award":["4000126830\/19\/I-BG"],"award-info":[{"award-number":["4000126830\/19\/I-BG"]}]},{"name":"European Space Agency (ESA)","award":["PRG330"],"award-info":[{"award-number":["PRG330"]}]},{"name":"Estonian Science Council","award":["4000126830\/19\/I-BG"],"award-info":[{"award-number":["4000126830\/19\/I-BG"]}]},{"name":"Estonian Science Council","award":["PRG330"],"award-info":[{"award-number":["PRG330"]}]},{"name":"University Library of Technical University of Munich","award":["4000126830\/19\/I-BG"],"award-info":[{"award-number":["4000126830\/19\/I-BG"]}]},{"name":"University Library of Technical University of Munich","award":["PRG330"],"award-info":[{"award-number":["PRG330"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>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 possibility of enhancing methods and procedures in order to develop a geodetic SAR positioning technique towards operability.<\/jats:p>","DOI":"10.3390\/rs14143250","type":"journal-article","created":{"date-parts":[[2022,7,6]],"date-time":"2022-07-06T21:15:52Z","timestamp":1657142152000},"page":"3250","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Geodetic SAR for Height System Unification and Sea Level Research\u2014Results in the Baltic Sea Test Network"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2615-3681","authenticated-orcid":false,"given":"Thomas","family":"Gruber","sequence":"first","affiliation":[{"name":"Astronomical and Physical Geodesy, School of Engineering and Design, Technical University of Munich (TUM), 80333 Munich, Germany"}]},{"given":"Jonas","family":"\u00c5gren","sequence":"additional","affiliation":[{"name":"Lantm\u00e4teriet (LM), Swedish Mapping, Cadastral and Land Registration Authority, 80182 Gavle, Sweden"}]},{"given":"Detlef","family":"Angermann","sequence":"additional","affiliation":[{"name":"Deutsches Geod\u00e4tisches Forschungsinstitut, School of Engineering and Design, Technical University of Munich (TUM), 80333 Munich, Germany"}]},{"given":"Artu","family":"Ellmann","sequence":"additional","affiliation":[{"name":"School of Engineering, Tallinn University of Technology (TUT), 19086 Tallinn, Estonia"}]},{"given":"Andreas","family":"Engfeldt","sequence":"additional","affiliation":[{"name":"Lantm\u00e4teriet (LM), Swedish Mapping, Cadastral and Land Registration Authority, 80182 Gavle, Sweden"}]},{"given":"Christoph","family":"Gisinger","sequence":"additional","affiliation":[{"name":"German Aerospace Center (DLR), Remote Sensing Technology, 82234 We\u00dfling, Germany"}]},{"given":"Leszek","family":"Jaworski","sequence":"additional","affiliation":[{"name":"Centrum Bada\u0144 Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), 00-716 Warsaw, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6738-741X","authenticated-orcid":false,"given":"Tomasz","family":"Kur","sequence":"additional","affiliation":[{"name":"Centrum Bada\u0144 Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), 00-716 Warsaw, Poland"}]},{"given":"Simo","family":"Marila","sequence":"additional","affiliation":[{"name":"Finnish Geospatial Research Institute (FGI), 02430 Masala, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1136-5609","authenticated-orcid":false,"given":"Jolanta","family":"Nastula","sequence":"additional","affiliation":[{"name":"Centrum Bada\u0144 Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), 00-716 Warsaw, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1744-7004","authenticated-orcid":false,"given":"Faramarz","family":"Nilfouroushan","sequence":"additional","affiliation":[{"name":"Lantm\u00e4teriet (LM), Swedish Mapping, Cadastral and Land Registration Authority, 80182 Gavle, Sweden"}]},{"given":"Maaria","family":"Nordman","sequence":"additional","affiliation":[{"name":"Finnish Geospatial Research Institute (FGI), 02430 Masala, Finland"},{"name":"School of Engineering, Aalto University (AU), 00076 Aalto, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9721-0589","authenticated-orcid":false,"given":"Markku","family":"Poutanen","sequence":"additional","affiliation":[{"name":"Finnish Geospatial Research Institute (FGI), 02430 Masala, Finland"}]},{"given":"Timo","family":"Saari","sequence":"additional","affiliation":[{"name":"Finnish Geospatial Research Institute (FGI), 02430 Masala, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0349-1274","authenticated-orcid":false,"given":"Marius","family":"Schlaak","sequence":"additional","affiliation":[{"name":"Astronomical and Physical Geodesy, School of Engineering and Design, Technical University of Munich (TUM), 80333 Munich, Germany"}]},{"given":"Anna","family":"\u015awi\u0105tek","sequence":"additional","affiliation":[{"name":"Centrum Bada\u0144 Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), 00-716 Warsaw, Poland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3031-8645","authenticated-orcid":false,"given":"Sander","family":"Varbla","sequence":"additional","affiliation":[{"name":"School of Engineering, Tallinn University of Technology (TUT), 19086 Tallinn, Estonia"}]},{"given":"Ryszard","family":"Zdunek","sequence":"additional","affiliation":[{"name":"Centrum Bada\u0144 Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), 00-716 Warsaw, Poland"}]}],"member":"1968","published-online":{"date-parts":[[2022,7,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Gruber, T., \u00c5gren, J., Angermann, D., Ellmann, A., Engfeldt, A., Gisinger, C., Jaworski, L., Marila, S., Nastula, J., and Nilfouroushan, F. 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