{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T16:08:07Z","timestamp":1775146087003,"version":"3.50.1"},"reference-count":41,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2019,10,31]],"date-time":"2019-10-31T00:00:00Z","timestamp":1572480000000},"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>Understanding the effects of Earth\u2019s surface topography on Global Navigation Satellite Systems Reflectometry (GNSS-R) space-borne data is important to calibrate experimental measurements, so as to provide accurate soil moisture content (SMC) retrievals. In this study, several scientific observables obtained from delay-Doppler maps (DDMs)      \u27e8      |   Y  r , t o p o   ( \u03c4 , f )  |    2   \u27e9      generated on board the Cyclone Global Navigation Satellite System (CyGNSS) mission were evaluated as a function of several topographic parameters derived from a digital elevation model (DEM). This assessment was performed as a function of Soil Moisture Active Passive (SMAP)-derived SMC at grazing angles      \u03b8 e     ~ [20,30] \u00b0 and in a nadir-looking configuration      \u03b8 e     ~ [80,90] \u00b0. Global scale results showed that the width of the trailing edge (TE) was small     T E    ~ [100, 250] m and the reflectivity was high    \u0393   ~ [\u201310, \u20133] dB over flat areas with low topographic heterogeneity, because of an increasing coherence of Earth-reflected Global Positioning System (GPS) signals. However, the strong impact of several topographic features over areas with rough topography provided motivation to perform a parametric analysis. A specific target area with little vegetation, low small-scale surface roughness, and a wide variety of terrains in South Asia was selected. A significant influence of several topographic parameters i.e., surface slopes and curvatures was observed. This triggered our study of the sensitivity of     T E     and    \u0393    to SMC and topographic wetness index (    T W I    ). Regional scale results showed that     T E     and    \u0393    are strongly correlated with the     T W I    , while the sensitivity to SMC was almost negligible. The Pearson correlation coefficients of     T E     and    \u0393    with     T W I     are      r \u0393     ~ 0.59 and      r  T E      ~\u22120.63 at      \u03b8 e     ~ [20, 30] \u00b0 and      r \u0393     ~ 0.48 and      r  T E      ~ \u22120.50 at      \u03b8 e     ~ [80, 90] \u00b0, respectively.<\/jats:p>","DOI":"10.3390\/rs11212556","type":"journal-article","created":{"date-parts":[[2019,10,31]],"date-time":"2019-10-31T06:33:29Z","timestamp":1572503609000},"page":"2556","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["First Evaluation of Topography on GNSS-R: An Empirical Study Based on a Digital Elevation Model"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7775-7314","authenticated-orcid":false,"given":"Hugo","family":"Carreno-Luengo","sequence":"first","affiliation":[{"name":"Centre Tecn\u00f2logic de Telecomunicacions de Catalunya (CTTC\/CERCA), 08860 Castelldefels (Barcelona), Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8924-9029","authenticated-orcid":false,"given":"Guido","family":"Luzi","sequence":"additional","affiliation":[{"name":"Centre Tecn\u00f2logic de Telecomunicacions de Catalunya (CTTC\/CERCA), 08860 Castelldefels (Barcelona), Spain"}]},{"given":"Michele","family":"Crosetto","sequence":"additional","affiliation":[{"name":"Centre Tecn\u00f2logic de Telecomunicacions de Catalunya (CTTC\/CERCA), 08860 Castelldefels (Barcelona), Spain"}]}],"member":"1968","published-online":{"date-parts":[[2019,10,31]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1296","DOI":"10.1029\/WR006i005p01296","article-title":"Partial area contributions to storm runoff in a small New England watershed","volume":"6","author":"Dunne","year":"1970","journal-title":"Water Resour. 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