{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:24:33Z","timestamp":1760243073073,"version":"build-2065373602"},"reference-count":39,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2015,6,5]],"date-time":"2015-06-05T00:00:00Z","timestamp":1433462400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The scattering of GNSS signals over a water surface is studied when the receiver is at a low height, as in GNSS-R coastal altimetry. The precise determination of the local sea level and wave state from the coast will provide useful altimetry and wave information as \u201cdry\u201d tide and wave gauges. An experiment has been conducted at the Canal d'Investigaci\u00f3 i Experimentaci\u00f3 Mar\u00edtima (CIEM) wave channel for two simulated \u201csea\u201d states. The  GNSS-reflectometer used is the P(Y) and C\/A ReflectOmeter (PYCARO) instrument,  a closed-loop receiver with delay and Doppler tracking loops that uses the conventional GNSS-R technique for the GPS C\/A code. After retracking of the scattered GPS signals, the coherent and incoherent components have been studied. To reproduce the transmitted GPS signals indoors, a Rohde and Schwarz signal generator is used. It is found that, despite the ratio of the coherent and incoherent components being ~1, the coherent component is strong enough that it can be tracked. The coherent component comes from clusters of points on the surface that approximately satisfy the specular reflection conditions (\u201croughed facet\u201d). The Pearson\u2019s linear correlation coefficients of the derived \u201csea\u201d surface height with the wave gauge data are: 0.78, 0.85 and 0.81 for a SWH = 36 cm and 0.34, 0.74, and 0.72 for a  SWH = 64 cm, respectively, for transmitter elevation angles of                                                    = 60\u00b0, 75\u00b0 and 86\u00b0, respectively. Finally, the rms phase of the received signal before the retracking processing is used to estimate the effective rms surface height of the \u2018facets\u2019, where the waves get scattered. It is found to be between 2.5- and 4.1-times smaller than the theoretical values corresponding to the half of the coherent reflectivity decaying factor.<\/jats:p>","DOI":"10.3390\/rs70607471","type":"journal-article","created":{"date-parts":[[2015,6,5]],"date-time":"2015-06-05T10:23:07Z","timestamp":1433499787000},"page":"7471-7493","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Empirical Results of a Surface-Level GNSS-R Experiment in a Wave Channel"],"prefix":"10.3390","volume":"7","author":[{"given":"Hugo","family":"Carreno-Luengo","sequence":"first","affiliation":[{"name":"BarcelonaTech Remote Sensing Laboratory and IEEC\/UPC, Universitat Polit\u00e8cnica de Catalunya, UPC Campus Nord, D3, 08034 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9514-4992","authenticated-orcid":false,"given":"Adriano","family":"Camps","sequence":"additional","affiliation":[{"name":"BarcelonaTech Remote Sensing Laboratory and IEEC\/UPC, Universitat Polit\u00e8cnica de Catalunya, UPC Campus Nord, D3, 08034 Barcelona, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2015,6,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2209","DOI":"10.1109\/TGRS.2010.2092431","article-title":"The PARIS ocean altimeter in-orbit demonstrator","volume":"49","author":"Buck","year":"2011","journal-title":"IEEE Trans. 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