{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T11:19:52Z","timestamp":1780485592159,"version":"3.54.1"},"reference-count":36,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2019,11,16]],"date-time":"2019-11-16T00:00:00Z","timestamp":1573862400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Research Project of Surveying Mapping and Geoinformation of Jiangsu","award":["JSCHKY 201903"],"award-info":[{"award-number":["JSCHKY 201903"]}]},{"name":"the State Key Program of National Science Foundation of China","award":["41830110"],"award-info":[{"award-number":["41830110"]}]},{"name":"Jiangsu Overseas Research &amp; Training Program for University Prominent Young &amp; Middle-aged Teachers and Presidents","award":["Null"],"award-info":[{"award-number":["Null"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Snow is one of the most critical sources of freshwater, which influences the global water cycle and climate change. However, it is difficult to monitor global snow variations with high spatial\u2013temporal resolution using traditional techniques due to their costly and labor-intensive nature. Nowadays, the Global Positioning System Interferometric Reflectometry (GPS-IR) technique can measure the average snow depth around a GPS antenna using its signal-to-noise ratio (SNR) data. Previous studies focused on the use of GPS data at sites located in flat areas or on very gentle slopes. In this contribution, we propose a strategy called the Tilted Surface Strategy (TSS), which uses the SNR data reflected only from the flat quadrants to estimate the snow depth instead of the conventional strategy, which employs all the SNR data reflected from the whole area around a GPS antenna. Three geodetic GPS sites from the Plate Boundary Observatory (PBO) project were chosen in this experimental study, of which GPS sites p683 and p101 were located on slopes with their gradients up to 18% and the site p025 was located on a flat area. Comparing the snow depths derived with the GPS-IR TSS method with the snow depth results provided with the GPS-PBO, i.e., GPS-IR with the conventional strategy, the Snowpack Telemetry (SNOTEL) network measurements and gridded Snow Data Assimilation System (SNODAS) estimates, it was found that the snow depths derived with the four methods had a good agreement, but the snow depth time series with the GPS-IR TSS method were closer to the SNOTEL measurements and the SNODAS estimates than those with GPS-PBO method. Similar observations were also obtained from the cumulative snowfall time series. Results generally indicated that for those GPS sites located on slopes, the TSS strategy works better.<\/jats:p>","DOI":"10.3390\/s19224994","type":"journal-article","created":{"date-parts":[[2019,11,18]],"date-time":"2019-11-18T04:31:10Z","timestamp":1574051470000},"page":"4994","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Snow Depth Estimation on Slopes Using GPS-Interferometric Reflectometry"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5551-3079","authenticated-orcid":false,"given":"Haohan","family":"Wei","sequence":"first","affiliation":[{"name":"College of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China"},{"name":"School of Electrical Engineering and Computer Science, Queensland University of Technology, Brisbane 4001, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5262-1007","authenticated-orcid":false,"given":"Xiufeng","family":"He","sequence":"additional","affiliation":[{"name":"School of Earth Science and Engineering, Hohai University, Nanjing 210098, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6548-3347","authenticated-orcid":false,"given":"Yanming","family":"Feng","sequence":"additional","affiliation":[{"name":"School of Electrical Engineering and Computer Science, Queensland University of Technology, Brisbane 4001, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5108-4828","authenticated-orcid":false,"given":"Shuanggen","family":"Jin","sequence":"additional","affiliation":[{"name":"Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5059-5327","authenticated-orcid":false,"given":"Fei","family":"Shen","sequence":"additional","affiliation":[{"name":"Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing 210046, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"752","DOI":"10.1109\/JPROC.2009.2038947","article-title":"Cold Regions Hydrology High-Resolution Observatory for Snow and Cold Land Processes","volume":"98","author":"Rott","year":"2010","journal-title":"IEEE Proc."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1038\/nature04141","article-title":"Potential impacts of a warming climate on water availability in snow-dominated regions","volume":"438","author":"Barnett","year":"2005","journal-title":"Nature"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1415","DOI":"10.5194\/hess-17-1415-2013","article-title":"From observation to the quantification of snow processes with a time-lapse camera network","volume":"17","author":"Garvelmann","year":"2013","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"868","DOI":"10.1016\/j.rse.2009.01.001","article-title":"Retrieval of subpixel snow covered area, grain size, and albedo from MODIS","volume":"113","author":"Painter","year":"2009","journal-title":"Remote Sens. Environ."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1016\/j.advwatres.2012.03.002","article-title":"Assessment of methods for mapping snow cover from MODIS","volume":"51","author":"Rittger","year":"2013","journal-title":"Adv. Water Resour."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2951","DOI":"10.1002\/hyp.8329","article-title":"Snow measurement by GPS interferometric reflectometry: An evaluation at Niwot Ridge, Colorado","volume":"26","author":"Gutmann","year":"2012","journal-title":"Hydrol. Process."},{"key":"ref_7","first-page":"139","article-title":"Dual-frequency GPS precise point positioning with WADGPS corrections","volume":"54","author":"Rho","year":"2007","journal-title":"Annu. Navig."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"296","DOI":"10.1179\/1752270615Y.0000000033","article-title":"An adaptive stochastic model for GPS observations and its performance in precise point positioning","volume":"48","author":"Zheng","year":"2016","journal-title":"Surv. Rev."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Reilinger, R., McClusky, S., Vernant, P., Lawrence, S., Ergintav, S., Cakmak, R., Ozener, H., Kadirov, F., Guliev, I., and Stepanyan, R. (2006). GPS constraints on continental deformation in the Africa-Arabia-Eurasia continental collision zone and implications for the dynamics of plate interactions. J. Geophys. Res.","DOI":"10.1029\/2005JB004051"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"4006","DOI":"10.3390\/rs5084006","article-title":"Physical Reflectivity and Polarization Characteristics for Snow and Ice-Covered Surfaces Interacting with GPS Signals","volume":"5","author":"Najibi","year":"2013","journal-title":"Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1623","DOI":"10.1016\/j.asr.2014.03.005","article-title":"Sensing snow height and surface temperature variations in Greenland from GPS reflected signals","volume":"53","author":"Jin","year":"2014","journal-title":"Adv. Space Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"951","DOI":"10.1109\/36.841977","article-title":"Scattering of GPS signals from the ocean with wind remote sensing application","volume":"38","author":"Zavorotny","year":"2000","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1007\/s10291-007-0076-6","article-title":"Using GPS multipath to measure soil moisture luctuations: Initial results","volume":"12","author":"Larson","year":"2008","journal-title":"GPS Solut."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"537","DOI":"10.1109\/TGRS.2013.2242332","article-title":"Effects of Near-Surface Soil Moisture on GPS SNR Data: Development of a Retrieval Algorithm for Soil Moisture","volume":"52","author":"Chew","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"L17502","DOI":"10.1029\/2009GL039430","article-title":"Can we measure snow depth with GPS receivers?","volume":"36","author":"Larson","year":"2009","journal-title":"Geophys. Res. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1007\/s10291-012-0259-7","article-title":"GPS snow sensing: Results from the EarthScope Plate Boundary Observatory","volume":"17","author":"Larson","year":"2013","journal-title":"GPS Solut."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"775","DOI":"10.1002\/wat2.1167","article-title":"GPS interferometric reflectometry: Applications to surface soil moisture, snow depth, and vegetation water content in the western United States","volume":"3","author":"Larson","year":"2016","journal-title":"Wiley Interdiscip. Rev. Water"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"309","DOI":"10.1007\/s10291-013-0331-y","article-title":"Forward modeling of GPS multipath for near-surface eflectometry and positioning applications","volume":"18","author":"Nievinski","year":"2014","journal-title":"GPS Solut."},{"key":"ref_19","first-page":"77","article-title":"Observations of signal-to-noise ratios (SNR) at geodetic GPS site CASA: Implications for phase multipath","volume":"23","author":"Bilich","year":"2004","journal-title":"Proc. Cent. Eur. Geodyn. Seismol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"6555","DOI":"10.1109\/TGRS.2013.2297681","article-title":"Inverse Modeling of GPS Multipath for Snow Depth Estimation\u2014Part I: Formulation and Simulations","volume":"52","author":"Nievinski","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"6564","DOI":"10.1109\/TGRS.2013.2297688","article-title":"Inverse Modeling of GPS Multipath for Snow Depth Estimation\u2014Part II: Application and Validation","volume":"52","author":"Nievinski","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"5100","DOI":"10.1109\/TGRS.2015.2417214","article-title":"Snow Depth Estimation Based on Multipath Phase Combination of GPS Triple-Frequency Signals","volume":"53","author":"Yu","year":"2015","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"6892","DOI":"10.1002\/2014WR015561","article-title":"Snow depth, density, and SWE estimates derived from GPS reflection data: Validation in the western U. S","volume":"50","author":"Mccreight","year":"2014","journal-title":"Water Resour. Res."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1104","DOI":"10.1016\/j.asr.2014.11.019","article-title":"Assessment of modernized GPS L5 SNR for ground-based multipath reflectometry applications","volume":"55","author":"Tabibi","year":"2015","journal-title":"Adv. Space Res."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Jin, S., Qian, X., and Kutoglu, H. (2016). Snow Depth Variations Estimated from GPS-Reflectometry: A Case Study in Alaska from L2P SNR Data. Remote Sens., 8.","DOI":"10.3390\/rs8010063"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2425","DOI":"10.1002\/hyp.10346","article-title":"Comparison of Snow Data Assimilation System with GPS reflectometry snow depth in the Western United States","volume":"29","author":"Boniface","year":"2015","journal-title":"Hydrol. Process."},{"key":"ref_27","unstructured":"(2017, October 30). The Plate Boundary Observatory Network, Colorado, USA. Available online: http:\/\/pbo.unavco.org."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"675","DOI":"10.1029\/2000WR900307","article-title":"Characteristics of large snowfall events in the montane western United States as examined using snowpack telemetry (SNOTEL) data","volume":"37","author":"Serreze","year":"2001","journal-title":"Water Resour. Res."},{"key":"ref_29","unstructured":"(2017, October 30). National Water and Climate Center, Oregon, USA. Available online: https:\/\/www.wcc.nrcs.usda.gov\/."},{"key":"ref_30","unstructured":"(2019, July 01). Snow Data Assimilation System of National Snow and Ice Data Center, Colorado, USA. Available online: https:\/\/nsidc.org\/data\/g02158."},{"key":"ref_31","unstructured":"Carroll, T., Cline, D., Fall, G., Nilsson, A., Li, L., and Rost, A. (2001, January 16\u201319). NOHRSC Operations and the Simulation of Snow Cover Properties for the Conterminous U.S.. Proceedings of the 69th Annual Meeting of the Western Snow Conference, Sun Valley, ID, USA."},{"key":"ref_32","unstructured":"Barrett, A.P. (2003). National Operational Hydrologic Remote Sensing Center Snow Data Assimilation System (SNODAS) Products at NSIDC, National Snow and Ice Data Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1109\/JSTARS.2009.2033612","article-title":"GPS multipath and its relation to near-surface soil moisture content","volume":"3","author":"Larson","year":"2010","journal-title":"IEEE J. Sel. Top. Appl. Earth Observ. Remote Sens."},{"key":"ref_34","unstructured":"Press, F., Teukolsky, S., Vetterling, W., and Flannery, B. (1996). Numerical Recipes in Fortran 90: The Art of Parallel Scientific Computing, Cambridge University Press. [2nd ed.]."},{"key":"ref_35","unstructured":"Axelrad, P., Larson, K., and Jones, B. (2005, January 13\u201316). Use of the Correct Satellite Repeat Period to Characterize and Reduce Site-Specific Multipath Errors. Proceedings of the ION GNSS 18th International Technical Meeting of the Satellite Division, Long Beach, CA, USA."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.rse.2005.09.015","article-title":"Utilizing Calibrated GPS Reflected Signals to Estimate Soil Reflectivity and Dielectric Constant: Results from SMEX02","volume":"100","author":"Katzberg","year":"2006","journal-title":"Remote Sens. Environ."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/22\/4994\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:35:02Z","timestamp":1760189702000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/22\/4994"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,11,16]]},"references-count":36,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2019,11]]}},"alternative-id":["s19224994"],"URL":"https:\/\/doi.org\/10.3390\/s19224994","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,11,16]]}}}