{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,27]],"date-time":"2026-06-27T15:44:48Z","timestamp":1782575088378,"version":"3.54.5"},"reference-count":45,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2022,9,16]],"date-time":"2022-09-16T00:00:00Z","timestamp":1663286400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Deutsches GeoForschungsZentrum (GFZ)"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>High-precision GNSS (global navigation satellite e system) measurements can be used for remote sensing and nowadays play a significant role in atmospheric sounding (station data, radio occultation observations) and sea surface altimetry based on reflectometry. A limiting factor of high-precision reflectometry is the loss of coherent phase information due to sea-state-induced surface roughness. This work studies airborne reflectometry observations recorded over coastal waters to examine the sea-state influence on Doppler distribution and the coherent residual phase retrieval. From coherent observations, the possibility of zenith total delay inversion is also investigated, considering the hydrostatic mapping factor from the Vienna mapping function and an exponential vertical decay factor depending on height receiver changes. The experiment consists of multiple flights performed along the coast between the cities of Calais and Boulogne-sur-Mer, France, in July 2019. Reflected signals acquired in a right-handed circular polarization are processed through a model-aided software receiver and passed through a retracking module to obtain the Doppler and phase-corrected signal. Results from grazing angle observations (elevation &lt; 15\u00b0) show a high sensitivity of Doppler spread with respect to sea state with correlations of 0.75 and 0.88 with significant wave height and wind speed, respectively. An empirical Doppler spread threshold of 0.5 Hz is established for coherent reflections supported by the residual phase observations obtained. Phase coherence occurs in 15% of the observations; however, the estimated zenith total delay for the best event corresponds to 2.44 m, which differs from the typical zenith total delay (2.3 m) of 5%.<\/jats:p>","DOI":"10.3390\/rs14184628","type":"journal-article","created":{"date-parts":[[2022,9,19]],"date-time":"2022-09-19T04:49:22Z","timestamp":1663562962000},"page":"4628","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Airborne Coherent GNSS Reflectometry and Zenith Total Delay Estimation over Coastal Waters"],"prefix":"10.3390","volume":"14","author":[{"given":"Mario","family":"Moreno","sequence":"first","affiliation":[{"name":"German Aerospace Centre, Institute of Solar-Terrestrial Physics (DLR-SO), Kalkhorstweg 53, 17235 Neustrelitz, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maximilian","family":"Semmling","sequence":"additional","affiliation":[{"name":"German Aerospace Centre, Institute of Solar-Terrestrial Physics (DLR-SO), Kalkhorstweg 53, 17235 Neustrelitz, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Georges","family":"Stienne","sequence":"additional","affiliation":[{"name":"Laboratoire d\u2019Informatique, Signal et Image de la C\u00f4te d\u2019Opale (LISIC), Universit\u00e9 Littoral C\u00f4te d\u2019Opale (ULCO), 50 rue Ferdinand Buisson, 62228 Calais, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wafa","family":"Dalil","sequence":"additional","affiliation":[{"name":"Laboratoire d\u2019Informatique, Signal et Image de la C\u00f4te d\u2019Opale (LISIC), Universit\u00e9 Littoral C\u00f4te d\u2019Opale (ULCO), 50 rue Ferdinand Buisson, 62228 Calais, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mainul","family":"Hoque","sequence":"additional","affiliation":[{"name":"German Aerospace Centre, Institute of Solar-Terrestrial Physics (DLR-SO), Kalkhorstweg 53, 17235 Neustrelitz, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jens","family":"Wickert","sequence":"additional","affiliation":[{"name":"German Research Centre for Geosciences (GFZ), Wissenschaftpark \u201cAlbert Einstein\u201d, Telegrafenberg, 14473 Potsdam, Germany"},{"name":"Institute of Geodesy and Geoinformation Science, Department of GNSS Remote Sensing, Navigation and Positioning, Technical University of Berlin (TUB), Str. des 17. Juni 135, 10623 Berlin, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Serge","family":"Reboul","sequence":"additional","affiliation":[{"name":"Laboratoire d\u2019Informatique, Signal et Image de la C\u00f4te d\u2019Opale (LISIC), Universit\u00e9 Littoral C\u00f4te d\u2019Opale (ULCO), 50 rue Ferdinand Buisson, 62228 Calais, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,9,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1002\/2013EF000188","article-title":"Sea Level Rise and Its Coastal Impacts","volume":"2","author":"Cazenave","year":"2014","journal-title":"Earth\u2019s Future"},{"key":"ref_2","unstructured":"ESA Climate Office (2021, November 24). Sea State. 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