{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T06:23:43Z","timestamp":1771482223353,"version":"3.50.1"},"reference-count":15,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2023,8,25]],"date-time":"2023-08-25T00:00:00Z","timestamp":1692921600000},"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>Today, land and ocean observations are crucial for monitoring climate change. The method of GNSS reflectometry is an opportunistic way to provide low-cost observations of many geophysical parameters. However, although this method has been the subject of numerous research studies, work is still in progress to improve its possibilities and fields of application. This paper focuses on GNSS reflectometry using carrier phase measurements for water altimetry measurements. The difficulties in implementing such a method lie in the need to collect a coherent signal and to solve the integer ambiguity value. In this context, the implementation of innovative signal processing is described, including the correlation of the reflected signals in dedicated software and the prolongation of the coherent integration time to enhance signal coherency. These processes were applied to data collected over Carcans-Hourtin Lake in France to compute the height of the reflection surface which was then compared to in situ GNSS buoy height measurements. The results show that at 300 ft (91.44 m), the differences between the lake heights measured with the buoy and with the reflectometry data can reach less than 1 cm for the L1, E1 and E5 GNSS signals. In addition, the slope of the geoid estimated with the reflectometry data is very consistent with that of the RAF20 geoid model, with a difference of up to less than 2 mm\/km.<\/jats:p>","DOI":"10.3390\/rs15174192","type":"journal-article","created":{"date-parts":[[2023,8,28]],"date-time":"2023-08-28T05:46:47Z","timestamp":1693201607000},"page":"4192","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Lake Altimetry Using Long Coherent Integration Carrier Phase Measurements from Airborne GNSS Reflectometry"],"prefix":"10.3390","volume":"15","author":[{"given":"Nolan","family":"Varais","sequence":"first","affiliation":[{"name":"Laboratoire G\u00e9omatique et Foncier (UR 4630), Conservatoire National des Arts et M\u00e9tiers (Cnam), Hesam Universit\u00e9, 72000 Le Mans, France"},{"name":"Centre National d\u2019Etudes Spatiales, 31400 Toulouse, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8887-9122","authenticated-orcid":false,"given":"J\u00e9r\u00f4me","family":"Verdun","sequence":"additional","affiliation":[{"name":"Laboratoire G\u00e9omatique et Foncier (UR 4630), Conservatoire National des Arts et M\u00e9tiers (Cnam), Hesam Universit\u00e9, 72000 Le Mans, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1657-786X","authenticated-orcid":false,"given":"Jos\u00e9","family":"Cali","sequence":"additional","affiliation":[{"name":"Laboratoire G\u00e9omatique et Foncier (UR 4630), Conservatoire National des Arts et M\u00e9tiers (Cnam), Hesam Universit\u00e9, 72000 Le Mans, France"}]},{"given":"Laurent","family":"Lestarquit","sequence":"additional","affiliation":[{"name":"Centre National d\u2019Etudes Spatiales, 31400 Toulouse, France"}]}],"member":"1968","published-online":{"date-parts":[[2023,8,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Hall, R.C.C. (1988, January 12\u201316). Multistatic scatterometry. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Edinburgh, UK.","DOI":"10.1109\/IGARSS.1988.570200"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"L24405","DOI":"10.1029\/2008GL036013","article-title":"Use of GPS receivers as a soil moisture network for water cycle studies","volume":"35","author":"Larson","year":"2008","journal-title":"Geophys. Res. Lett."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3616","DOI":"10.1109\/TGRS.2009.2030672","article-title":"Soil Moisture Retrieval Using GNSS-R Techniques: Experimental Results Over a Bare Soil Field","volume":"47","author":"Camps","year":"2009","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Munoz-Martin, J.F., Perez, A., Camps, A., Rib\u00f3, S., Cardellach, E., Stroeve, J., Nandan, V., Itkin, P., Tonboe, R., and Hendricks, S. (2020). Snow and Ice Thickness Retrievals Using GNSS-R: Preliminary Results of the MOSAiC Experiment. Remote Sens., 12.","DOI":"10.3390\/rs12244038"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1301","DOI":"10.1016\/j.asr.2012.04.017","article-title":"Coastal Sea level measurements using a single geodetic GPS receiver","volume":"51","author":"Larson","year":"2013","journal-title":"Adv. Space Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1016\/j.rse.2015.10.011","article-title":"Sea level monitoring and sea state estimate using a single geodetic receiver","volume":"171","author":"Roussel","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"4843","DOI":"10.1109\/JSTARS.2016.2568742","article-title":"Reflectometry With an Open-Source Software GNSS Receiver: Use Case With Carrier Phase Altimetry","volume":"9","author":"Lestarquit","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Born, M., Wolf, E., Bhatia, A.B., Clemmow, P.C., Gabor, D., Stokes, A.R., Taylor, A.M., Wayman, P.A., and Wilcock, W.L. (1999). Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, Cambridge University Press. [7th ed.].","DOI":"10.1017\/CBO9781139644181"},{"key":"ref_9","unstructured":"Fernandez-Prades, C., Arribas, J., Closas, P., Aviles, C., and Esteve, L. (2011, January 19\u201323). GNSS-SDR: An Open-Source Tool for Researchers and Developers. Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, USA."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1186\/1687-6180-2014-50","article-title":"Sea level measurements using multi-frequency GPS and GLONASS observations","volume":"2014","author":"Haas","year":"2014","journal-title":"EURASIP J. Adv. Signal Process."},{"key":"ref_11","unstructured":"Henriksen, S.W., Mancini, A., and Chovitz, B.H. (2013). Geophysical Monograph Series, American Geophysical Union."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1035","DOI":"10.1109\/JRPROC.1953.274297","article-title":"The Constants in the Equation for Atmospheric Refractive Index at Radio Frequencies","volume":"41","author":"Smith","year":"1953","journal-title":"Proc. IRE"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"803","DOI":"10.1029\/RS009i010p00803","article-title":"An improved equation for the radio refractive index of air","volume":"9","author":"Thayer","year":"1974","journal-title":"Radio Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1007\/s00190-007-0135-3","article-title":"Short Note: A global model of pressure and temperature for geodetic applications","volume":"81","author":"JBoehm","year":"2007","journal-title":"J. Geod."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"471","DOI":"10.1007\/BF02899809","article-title":"Theory of carrier phase ambiguity resolution","volume":"8","author":"Teunissen","year":"2003","journal-title":"Wuhan Univ. J. Nat. 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