{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T14:55:47Z","timestamp":1778684147980,"version":"3.51.4"},"reference-count":60,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2017,6,21]],"date-time":"2017-06-21T00:00:00Z","timestamp":1498003200000},"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>Spaceborne Synthetic Aperture Radar (SAR) interferometry has been utilised to acquire high-resolution Digital Elevation Models (DEMs) with wide coverage, particularly for persistently cloud-covered regions where stereophotogrammetry is hard to apply. Since the discovery of sand buried drainage systems by the Shuttle Imaging Radar-A (SIR-A) L-band mission in 1982, radar images have been exploited to map subsurface features beneath a sandy cover of extremely low loss and low bulk humidity in some hyper-arid regions such as from the Japanese Earth Resources Satellite 1 (JERS-1) and Advanced Land Observing Satellite\/Phased Array type L-band Synthetic Aperture Radar (ALOS\/PALSAR). Therefore, we hypothesise that a Digital Elevation Model (DEM) derived by InSAR in hyper-arid regions is likely to represent a subsurface elevation model, especially for lower frequency radar systems, such as the L-band system (1.25 GHz). In this paper, we compare the surface appearance of radar images (L-band and C-band) with that of optical images to demonstrate their different abilities to show subsurface features. Moreover, we present an application of L-band InSAR to measure penetration depths in the eastern Sahara Desert. We demonstrate how the retrieved L-band InSAR DEM appears to be of a consistently 1\u20132 m lower elevation than the C-band Shuttle Radar Topography Mission (SRTM) DEM over sandy covered areas, which indicates the occurrence of penetration and confirms previous studies.<\/jats:p>","DOI":"10.3390\/rs9060638","type":"journal-article","created":{"date-parts":[[2017,6,22]],"date-time":"2017-06-22T02:39:15Z","timestamp":1498099155000},"page":"638","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["The Application of ALOS\/PALSAR InSAR to Measure Subsurface Penetration Depths in Deserts"],"prefix":"10.3390","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1054-121X","authenticated-orcid":false,"given":"Siting","family":"Xiong","sequence":"first","affiliation":[{"name":"Imaging Group, Mullard Space Science Laboratory (MSSL), Department of Space & Climate Physics, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5077-3736","authenticated-orcid":false,"given":"Jan-Peter","family":"Muller","sequence":"additional","affiliation":[{"name":"Imaging Group, Mullard Space Science Laboratory (MSSL), Department of Space & Climate Physics, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gang","family":"Li","sequence":"additional","affiliation":[{"name":"Institute of Space and Earth Information Science, The Chinese University of Hong Kong, New Territories, Hong Kong, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,6,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1109\/MSPEC.1982.6367027","article-title":"Spaceborne imaging radars probe \u2018in depth\u2019: New spaceborne radar sensors allow all-weather, day or night, high-resolution imaging of the earth\u2019s land and ocean surfaces","volume":"19","author":"Elachi","year":"1982","journal-title":"IEEE Spectr."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1004","DOI":"10.1126\/science.218.4576.1004","article-title":"Subsurface valleys and geoarcheology of the eastern Sahara revealed by shuttle radar","volume":"218","author":"McCauley","year":"1982","journal-title":"Science"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"674","DOI":"10.1109\/TAP.1975.1141170","article-title":"Coherent electromagnetic losses by scattering from volume inhomogeneities","volume":"23","author":"Roth","year":"1975","journal-title":"IEEE Trans. Antennas Propag."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1016\/S0034-4257(96)00143-5","article-title":"The use of multifrequency and polarimetric SIR-C\/X-SAR data in geologic studies of Bir Safsaf, Egpyt","volume":"59","author":"Schaber","year":"1997","journal-title":"Remote Sens. Environ."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1016\/j.jafrearsci.2005.10.012","article-title":"Use of radar data to delineate paleodrainage leading to the Kufra Oasis in the eastern Sahara","volume":"44","author":"Robinson","year":"2006","journal-title":"J. Afr. Earth Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1006\/jare.1999.0581","article-title":"Fluvio-aeolian dynamics in the north-eastern Sahara: The relationship between fluvial\/aeolian systems and ground-water concentration","volume":"44","author":"Maingue","year":"2000","journal-title":"J. Arid Environ."},{"key":"ref_7","first-page":"745","article-title":"Use of radar data to delineate palaeodrainage flow directions in the Selima Sand Sheet, eastern Sahara","volume":"66","author":"Robinson","year":"2000","journal-title":"Photogramm. Eng. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1007\/BF02959455","article-title":"Subsurface old drainage detection and paleoenvironment analysis using spaceborne radar images in Alxa Plateau","volume":"43","author":"Guo","year":"2000","journal-title":"Sci. China Ser. D Earth Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"220","DOI":"10.1016\/j.jafrearsci.2005.10.015","article-title":"Surface and subsurface structural mapping using low frequency radar: A synthesis of the Mauritanian and Egyptian experiments","volume":"44","author":"Grandjean","year":"2006","journal-title":"J. Afr. Earth Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/j.epsl.2008.10.029","article-title":"Mapping of a major paleodrainage system in eastern Libya using orbital imaging radar: The Kufrah River","volume":"277","author":"Paillou","year":"2009","journal-title":"Earth Planet. Sci. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"632","DOI":"10.1109\/JSTARS.2010.2056915","article-title":"Mapping subsurface geology in Sahara using L- and SAR: First results from the ALOS\/PALSAR imaging radar","volume":"3","author":"Paillou","year":"2010","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1016\/j.jaridenv.2015.02.020","article-title":"Mapping potential shallow groundwater in the Gobi desert using remote sensing: Lake Ulaan Nuur","volume":"118","author":"Sternberg","year":"2015","journal-title":"J. Arid Environ."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"770","DOI":"10.1016\/j.crte.2009.03.004","article-title":"Assessment of Holocene surface hydrological connections for the Ounianga lake catchment zone (Chad)","volume":"341","author":"Grenier","year":"2009","journal-title":"C. R. Geosci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1038\/srep08960","article-title":"Satellite-based estimates of groundwater depletion in the Badain Jaran Desert, China","volume":"5","author":"Jiao","year":"2015","journal-title":"Sci. Rep."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"658","DOI":"10.1016\/j.jaridenv.2006.11.018","article-title":"The application of radar topographic data to mapping of a mega- paleodrainage in the eastern Sahara","volume":"69","author":"Ghoneim","year":"2007","journal-title":"J. Arid Environ."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2319","DOI":"10.1109\/TGRS.2007.896613","article-title":"InSAR elevation bias caused by penetration into uniform volumes","volume":"45","author":"Dall","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_17","unstructured":"Wang, R., Hu, C., Zeng, T., Long, T., and Yuan, K. (2014, January 13\u201318). Subsurface Height Measurement Using InSAR Technique in Sand-Covered Arid Areas. Proceedings of the IEEE International Geoscience Remote Sensing Symposium, Qu\u00e9bec, QC, Canada."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"3550","DOI":"10.1109\/TGRS.2010.2047110","article-title":"Mapping of sand layer thickness in deserts using SAR interferometry","volume":"48","author":"Elsherbini","year":"2010","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1245","DOI":"10.1109\/36.927447","article-title":"Subsurface structures detection by combining L-band polarimetric SAR and GPR data: Example of the Pyla Dune (France)","volume":"39","author":"Grandjean","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1683","DOI":"10.1109\/TGRS.2004.830645","article-title":"A phase signature for detecting wet subsurface structures using polarimetric L-band SAR","volume":"42","author":"Lasne","year":"2004","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_21","unstructured":"NASA (2017, June 16). U.S. Releases Enhanced Shuttle Land Elevation Data, Available online: https:\/\/www.jpl.nasa.gov\/news\/news.php?release=2014-321."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/j.isprsjprs.2012.06.002","article-title":"Operational TanDEM-X DEM calibration and first validation results","volume":"73","author":"Gruber","year":"2012","journal-title":"ISPRS J. Photogramm. Remote Sens."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3307","DOI":"10.1109\/TGRS.2007.901027","article-title":"ALOS PALSAR: A Pathfinder Mission for Global-scale Monitoring of the Environment","volume":"45","author":"Rosenqvist","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"3725","DOI":"10.1109\/TGRS.2012.2187300","article-title":"Technical methodology for ASTER Global DEM","volume":"50","author":"Fujisada","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"71","DOI":"10.5194\/isprsannals-II-4-71-2014","article-title":"Precise global DEM generation by ALOS PRISM","volume":"II-4","author":"Tadono","year":"2014","journal-title":"ISPRS Ann. Photogramm. Remote Sens. Spat. Inf. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1016\/S0264-3707(02)00042-X","article-title":"ICESat\u2019s laser measurements of polar ice, atmosphere, ocean and land","volume":"34","author":"Zwally","year":"2002","journal-title":"J. Geodyn."},{"key":"ref_27","unstructured":"Tawadros, E. (2001). Geology of Egypt and Libya, Walter de Gruyter."},{"key":"ref_28","first-page":"719","article-title":"Stratigraphic and tectonic framework of Libya","volume":"51","author":"Conant","year":"1967","journal-title":"AAPG Bull."},{"key":"ref_29","unstructured":"Paillou, P., and Rosenqvist, A. (2003, January 21\u201325). The SAHARASAR Project: Potential support to water prospecting in arid Africa by SAR. Proceedings of the IEEE International Geoscience Remote Sensing Symposium, Toulouse, France."},{"key":"ref_30","unstructured":"Hermina, M. (1990). The surroundings of Kharga, Dakhla and Farafra Oases. The Geology of Egypt, Taylor & Francis Group, CRC Press."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"693","DOI":"10.1016\/S0264-8172(99)00013-6","article-title":"Re-evaluation of the petroleum potential of the Kufra Basin (SE Libya, ne Chad): Does the source rock barrier fall?","volume":"16","author":"Craig","year":"1999","journal-title":"Mar. Pet. Geol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1007\/s10040-006-0091-7","article-title":"The Nubian aquifer in southwest Egypt","volume":"15","author":"Robinson","year":"2007","journal-title":"Hydrogeol. J."},{"key":"ref_33","unstructured":"(2017, April 14). Nubian Sandstone Aquifer System. Available online: https:\/\/en.wikipedia.org\/wiki\/Nubian_Sandstone_Aquifer_System."},{"key":"ref_34","unstructured":"(2017, February 15). The Shuttle Radar Topography Mission (SRTM) Collection User Guide, Available online: https:\/\/lpdaac.usgs.gov\/sites\/default\/files\/public\/measures\/docs\/NASA_SRTM_V3.pdf."},{"key":"ref_35","unstructured":"Meer, F. (2001). Radar System Theory and Interferometric Processing. Radar Interferometry: Data Interpretation and Error Analysis, Kluwer Academic Publishers."},{"key":"ref_36","unstructured":"(2017, June 15). ROI_PAC Repeat Orbit Interferometry Package. Available online: http:\/\/www.openchannelfoundation.org\/projects\/ROI_PAC\/."},{"key":"ref_37","unstructured":"(2017, February 15). InSAR Principles: Guidelines for SAR Interferometry Processing and Interpretation (ESA TM-19). Available online: http:\/\/www.esa.int\/About_Us\/ESA_Publications\/InSAR_Principles_Guidelines_for_SAR_Interferometry_Processing_and_Interpretation_br_ESA_TM-19."},{"key":"ref_38","unstructured":"(2017, May 21). WGS 84 EGM96 15-Minute Geoid Height File and Coefficient File. Available online: http:\/\/earth-info.nga.mil\/GandG\/wgs84\/gravitymod\/egm96\/egm96.html."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1709","DOI":"10.1109\/TGRS.2002.802453","article-title":"Phase unwrapping for large SAR interferomgrams: Statistical segmentation and generalised network model","volume":"40","author":"Chen","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_40","unstructured":"Wegmuller, U., Werner, C., Strozzi, T., and Wiesmann, A. (August, January 31). Ionospheric Electron Concentration Effects on SAR and InSAR. Proceedings of the IEEE International Geoscience Remote Sensing Symposium, Denver, CO, USA."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1227","DOI":"10.1109\/TGRS.2011.2164805","article-title":"Ionospheric artifacts in simultaneous L-band InSAR and GPS observations","volume":"50","author":"Chen","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"3343","DOI":"10.1080\/01431160802562172","article-title":"Advanced InSAR atmospheric correction: MERIS\/MODIS combination and stacked water vapour models","volume":"30","author":"Li","year":"2009","journal-title":"Int. J. Remote Sens."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"L17311","DOI":"10.1029\/2011GL048757","article-title":"Systematic InSAR tropospheric phase delay corrections from global meteorological reanalysis data","volume":"38","author":"Jolivet","year":"2011","journal-title":"Geophys. Res. Lett."},{"key":"ref_44","unstructured":"(2017, May 21). OneGeology Portal. Available online: http:\/\/portal.onegeology.org\/OnegeologyGlobal\/."},{"key":"ref_45","unstructured":"(2017, May 21). USGS-Earthquake Hazards Program, Available online: https:\/\/earthquake.usgs.gov\/earthquakes\/search\/."},{"key":"ref_46","unstructured":"Hamling, I.-J., and Aoudia, A. (2011, January 5\u20139). Interaction between the North-West Sahara Aquifer and the seismically active intraplate Hun Graben Fault system, Libya. Proceedings of the American Geophysical Union (AGU) Fall Meeting, San Francisco, CA, USA."},{"key":"ref_47","unstructured":"Kampes, B., and Stefania, U. (1999, January 16\u201320). Doris: The Delft Object-Oriented Radar Interferometric Software. Proceedings of the 2nd International Symposium on Operationalization of Remote Sensing, Enschede, The Netherlands."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"725","DOI":"10.1080\/01431160110040323","article-title":"An assessment of support vector machines for land cover classification","volume":"23","author":"Huang","year":"2002","journal-title":"Int. J. Remote Sens."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Wang, R., Muller, J.P., Hu, C., and Zeng, T. (2015, January 14\u201316). Comparison between SRTM-C DEM and ICESat Elevation Data in the Arid Kufrah Area. Proceedings of the 2015 IET International Radar Conference, Hangzhou, China.","DOI":"10.1049\/cp.2015.1301"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/j.gloplacha.2016.12.018","article-title":"Recent Decadal Glacier Mass Balances over the Western Nyainqentanglha Mountains and the Increase in Their Melting Contribution to Nam Co Lake Measured by Differential Bistatic SAR Interferometry","volume":"149","author":"Li","year":"2017","journal-title":"Glob. Planet. Chang."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"557","DOI":"10.5194\/tc-9-557-2015","article-title":"Brief Communication: Contending Estimates of 2003\u20132008 Glacier Mass Balance over the Pamir\u2013Karakoram\u2013Himalaya","volume":"9","author":"Treichler","year":"2015","journal-title":"Cryosphere"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1885","DOI":"10.5194\/tc-7-1885-2013","article-title":"Corrigendum to Region-Wide Glacier Mass Balances over the Pamir-Karakoram-Himalaya during 1999\u20132011","volume":"7","author":"Gardelle","year":"2013","journal-title":"Cryosphere"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"261","DOI":"10.14358\/PERS.72.3.261","article-title":"How complementary are SRTM-X and \u2013C band Digital Elevation Models?","volume":"72","author":"Hoffmann","year":"2006","journal-title":"Photogramm. Eng. Remote Sens."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1957","DOI":"10.3390\/rs3091957","article-title":"ICESat\/GLAS Data as a Measurement Tool for Peatland Topography and Peat Swamp Forest Biomass in Kalimantan, Indonesia","volume":"3","author":"Ballhorn","year":"2011","journal-title":"Remote Sens."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"287","DOI":"10.14358\/PERS.72.3.287","article-title":"SRTM C-band and ICESat laser altimetry elevation comparisons as a function of tree cover and relief","volume":"72","author":"Carabajal","year":"2006","journal-title":"Photogramm. Eng. Remote Sens."},{"key":"ref_56","unstructured":"(2015, August 24). Website of NASA Distributed Active Archive Center (DAAC) at NSIDC\u2014Frequently Asked Questions. Available online: https:\/\/nsidc.org\/data\/icesat\/faq.html#9_all."},{"key":"ref_57","unstructured":"Xiong, S., Zeng, Q., Jiao, J., Gao, S., and Zhang, X. (2014, January 13\u201318). Improvement of PS-InSAR Atmospheric Phase Estimation by Using WRF Model. Proceedings of the IEEE International Geoscience Remote Sensing Symposium, Qu\u00e9bec, QC, Canada."},{"key":"ref_58","doi-asserted-by":"crossref","unstructured":"Li, Z., Muller, J.-P., and Cross, P. (2003). Comparison of precipitable water vapour derived from radiosonde, GPS and Moderate-Resolution Imaging Spectroradiometer measurements. J. Geophys. Res. Atmos., 108.","DOI":"10.1029\/2003JD003372"},{"key":"ref_59","unstructured":"MacDonald, A.M., Bonsor, H.C., Calow, R.C., Taylor, R.G., Lapworth, D.J., Maurice, L., Tucker, J., and \u00d3 Dochartaigh, B.\u00c9. (2011). Groundwater Resilience to Climate Change in Africa. British Geological Survey Open Report, OR\/11\/031, British Geological Survey."},{"key":"ref_60","unstructured":"Buis, A. (2017, June 16). NASA Mars Research Helps Find Buried Water on Earth, Available online: http:\/\/www.jpl.nasa.gov\/news\/news.php?release=2011-290."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/6\/638\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:39:53Z","timestamp":1760207993000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/6\/638"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,6,21]]},"references-count":60,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2017,6]]}},"alternative-id":["rs9060638"],"URL":"https:\/\/doi.org\/10.3390\/rs9060638","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,6,21]]}}}