{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:34:08Z","timestamp":1760240048736,"version":"build-2065373602"},"reference-count":37,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2019,3,2]],"date-time":"2019-03-02T00:00:00Z","timestamp":1551484800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["ESP2015-70014-C2-2-R"],"award-info":[{"award-number":["ESP2015-70014-C2-2-R"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]},{"name":"ESA contract","award":["RFQ\/3-12747\/09\/NL\/JD-CCN4"],"award-info":[{"award-number":["RFQ\/3-12747\/09\/NL\/JD-CCN4"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>This paper evaluates the capability of interferometric global navigation satellite system reflectometry (GNSS-R) to perform sea surface altimetry in a synoptic scenario. Such purpose, which requires the combination of the results from different GNSS signals, constitutes a unique characteristic of this approach. Interferometric GNSS-R group delay altimetry has been proven to be more precise than conventional GNSS-R. However, the self-consistency and accuracy of their synoptic solutions (simultaneous multi-static results) have never been proved before. In our work, we analyze a dataset of GNSS signals reflected off the Baltic Sea acquired during an airborne campaign using a receiver that was developed for such a purpose. Among other features, it enables beamformer capability in post-processing to get multiple and simultaneous GNSS signals under the interferometric approach\u2019s restrictions. In particular, the signals from two GPS and two Galileo satellites, at two frequency bands (L1 and L5), covering an elevation range between 28\u00b0 and 83\u00b0, are processed to retrieve sea surface height estimations. The results obtained are self-consistent among the different GNSS signals and data tracks, with discrepancies between 0.01 and 0.26 m. Overall, they agree with ancillary information at 0.40 m level, following a characteristic height gradient present at the experimental site.<\/jats:p>","DOI":"10.3390\/rs11050505","type":"journal-article","created":{"date-parts":[[2019,3,4]],"date-time":"2019-03-04T05:45:36Z","timestamp":1551678336000},"page":"505","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Is Accurate Synoptic Altimetry Achievable by Means of Interferometric GNSS-R?"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8100-1520","authenticated-orcid":false,"given":"Fran","family":"Fabra","sequence":"first","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8908-0972","authenticated-orcid":false,"given":"Estel","family":"Cardellach","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9173-8355","authenticated-orcid":false,"given":"Serni","family":"Rib\u00f3","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6215-7607","authenticated-orcid":false,"given":"Weiqiang","family":"Li","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5947-2649","authenticated-orcid":false,"given":"Antonio","family":"Rius","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"given":"Juan Carlos","family":"Arco-Fern\u00e1ndez","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"given":"Oleguer","family":"Nogu\u00e9s-Correig","sequence":"additional","affiliation":[{"name":"Earth Observation Research Group, Institute of Space Sciences (ICE, CSIC), 08193 Barcelona, Spain"},{"name":"Institut d\u2019Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain"}]},{"given":"Jaan","family":"Praks","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Aalto University, 02150 Espoo, Finland"}]},{"given":"Erkka","family":"Rouhe","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8414-7365","authenticated-orcid":false,"given":"Jaakko","family":"Sepp\u00e4nen","sequence":"additional","affiliation":[{"name":"Department of Electronics and Nanoengineering, Aalto University, 02150 Espoo, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7626-7033","authenticated-orcid":false,"given":"Manuel","family":"Mart\u00edn-Neira","sequence":"additional","affiliation":[{"name":"European Space Research and Technology Centre, European Space Agency, 2200 AG Noordwijk, The Netherlands"}]}],"member":"1968","published-online":{"date-parts":[[2019,3,2]]},"reference":[{"key":"ref_1","first-page":"331","article-title":"A passive reflectometry and interferometry system (PARIS): Application to ocean altimetry","volume":"17","year":"1993","journal-title":"ESA J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2011RS004683","article-title":"GNSS-R ground-based and airborne campaigns for ocean, land, ice, and snow techniques: Application to the GOLD-RTR data sets","volume":"46","author":"Cardellach","year":"2011","journal-title":"Radio Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1109\/MGRS.2014.2374220","article-title":"Tutorial on Remote Sensing Using GNSS Bistatic Radar of Opportunity","volume":"2","author":"Zavorotny","year":"2014","journal-title":"IEEE Geosci. 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