{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,6]],"date-time":"2025-12-06T05:00:06Z","timestamp":1764997206283,"version":"build-2065373602"},"reference-count":38,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2019,2,26]],"date-time":"2019-02-26T00:00:00Z","timestamp":1551139200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"CNRS-L, AUF, UM","award":["CNRS-L, AUF, UM"],"award-info":[{"award-number":["CNRS-L, AUF, UM"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Developing and enhancing strategies to characterize actual forests structure is a timely challenge, particularly for tropical forests. P-band synthetic aperture radar (SAR) tomography (TomoSAR) has previously been demonstrated as a powerful tool for characterizing the 3-D vertical structure of tropical forests, and its capability and potential to retrieve tropical forest structure has been discussed and assessed. On the other hand, the abilities of L-band TomoSAR are still in the early stages of development. Here, we aim to provide a better understanding of L-band TomoSAR capabilities for retrieving the 3-D structure of tropical forests and estimating the top height in dense forests. We carried out tomographic analysis using L-band UAVSAR data from the AfriSAR campaign conducted over Gabon Lop\u00e9 Park in February 2016. First, it was found that L-band TomoSAR was able to penetrate into and through the canopy down to the ground, and thus the canopy and ground layers were detected correctly. The resulting TomoSAR vertical profiles were validated with a digital terrain model and canopy height model extracted from small-footprint Lidar (SFL) data. Second, there was a strong correlation between the L-band Capon beam forming profile in HH and HV polarizations with Land Vegetation Ice Sensor (LVIS) Level 1B waveform Lidar over different kinds of forest in Gabon Lop\u00e9 National Park. Finally, forest top height from the L-band data was estimated and validated with SFL data, resulting in a root mean square error of 3 m and coefficient of determination of 0.92. The results demonstrate that L-band TomoSAR is capable of characterizing 3-D structure of tropical forests.<\/jats:p>","DOI":"10.3390\/rs11050475","type":"journal-article","created":{"date-parts":[[2019,2,26]],"date-time":"2019-02-26T11:00:44Z","timestamp":1551178844000},"page":"475","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["L-Band UAVSAR Tomographic Imaging in Dense Forests: Gabon Forests"],"prefix":"10.3390","volume":"11","author":[{"given":"Ibrahim","family":"El Moussawi","sequence":"first","affiliation":[{"name":"National Research Institute of Science and Technology for Environment and Agriculture (IRSTEA), University of Montpellier, Land Environment Remote Sensing and Spatial Information (TETIS), 34090 Montpellier, France"},{"name":"National Center for Remote Sensing, National Council for Scientific Research (CNRS), Riad al Soloh, 1107 2260 Beirut, Lebanon"},{"name":"Doctoral School of Sciences and Technologies, Lebanese University (LU), 1003 Beirut, Lebanon"},{"name":"Laboratory of Informatics, Robotics, and Microelectronics of Montpellier (LIRMM), University of Montpellier, 34392 Montpellier CEDEX 5, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0116-1642","authenticated-orcid":false,"given":"Dinh","family":"Ho Tong Minh","sequence":"additional","affiliation":[{"name":"National Research Institute of Science and Technology for Environment and Agriculture (IRSTEA), University of Montpellier, Land Environment Remote Sensing and Spatial Information (TETIS), 34090 Montpellier, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9461-4120","authenticated-orcid":false,"given":"Nicolas","family":"Baghdadi","sequence":"additional","affiliation":[{"name":"National Research Institute of Science and Technology for Environment and Agriculture (IRSTEA), University of Montpellier, Land Environment Remote Sensing and Spatial Information (TETIS), 34090 Montpellier, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4800-2270","authenticated-orcid":false,"given":"Chadi","family":"Abdallah","sequence":"additional","affiliation":[{"name":"National Center for Remote Sensing, National Council for Scientific Research (CNRS), Riad al Soloh, 1107 2260 Beirut, Lebanon"}]},{"given":"Jalal","family":"Jomaah","sequence":"additional","affiliation":[{"name":"Doctoral School of Sciences and Technologies, Lebanese University (LU), 1003 Beirut, Lebanon"}]},{"given":"Olivier","family":"Strauss","sequence":"additional","affiliation":[{"name":"Laboratory of Informatics, Robotics, and Microelectronics of Montpellier (LIRMM), University of Montpellier, 34392 Montpellier CEDEX 5, France"}]},{"given":"Marco","family":"Lavalle","sequence":"additional","affiliation":[{"name":"National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109, USA"}]}],"member":"1968","published-online":{"date-parts":[[2019,2,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"988","DOI":"10.1126\/science.1201609","article-title":"A large and persistent carbon sink in the world\u2019s forests","volume":"333","author":"Pan","year":"2011","journal-title":"Science"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Lou, Y., Hensley, S., Hawkins, B., Jones, C., Lavalle, M., Michel, T., Moller, D., Muellerschoen, R., Pinto, N., and Wu, X. (2017, January 23\u201328). Uavsar program: Recent upgrades to support vegetation structure studies and land ICE topography mapping. Proceedings of the 2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Fort Worth, TX, USA.","DOI":"10.1109\/IGARSS.2017.8128350"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1016\/S0034-4257(01)00281-4","article-title":"Estimation of tropical forest structural characteristics using large-footprint lidar","volume":"79","author":"Drake","year":"2002","journal-title":"Remote Sens. Environ."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Dubayah, R.O., Sheldon, S., Clark, D.B., Hofton, M., Blair, J.B., Hurtt, G.C., and Chazdon, R.L. (2010). Estimation of tropical forest height and biomass dynamics using lidar remote sensing at La Selva, Costa Rica. J. Geophys. Res. Biogeosci., 115.","DOI":"10.1029\/2009JG000933"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Cazcarra-Bes, V., Tello-Alonso, M., Fischer, R., Heym, M., and Papathanassiou, K. (2017). Monitoring of forest structure dynamics by means of L-band SAR tomography. Remote Sens., 9.","DOI":"10.3390\/rs9121229"},{"key":"ref_6","first-page":"19","article-title":"Lidar remote sensing for ecosystem studies: Lidar, an emerging remote sensing technology that directly measures the three-dimensional distribution of plant canopies, can accurately estimate vegetation structural attributes and should be of particular interest to forest, landscape, and global ecologists","volume":"52","author":"Lefsky","year":"2002","journal-title":"AIBS Bull."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2352","DOI":"10.1109\/36.964971","article-title":"Single-baseline polarimetric SAR interferometry","volume":"39","author":"Papathanassiou","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2142","DOI":"10.1109\/36.868873","article-title":"First demonstration of airborne SAR tomography using multibaseline L-band data","volume":"38","author":"Reigber","year":"2000","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Kramer, H.J. (2002). Observation of the Earth and Its Environment: Survey of Missions and Sensors, Springer Science & Business Media.","DOI":"10.1007\/978-3-642-56294-5"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1583","DOI":"10.1109\/5.118982","article-title":"Imaging radar polarimetry: A review","volume":"79","author":"Zebker","year":"1991","journal-title":"Proc. IEEE"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1109\/36.551929","article-title":"The potential of multifrequency polarimetric SAR in assessing agricultural and arboreous biomass","volume":"35","author":"Ferrazzoli","year":"1997","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"683","DOI":"10.1109\/TGRS.2005.843958","article-title":"Retrieval of biophysical parameters of agricultural crops using polarimetric SAR interferometry","volume":"43","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"402","DOI":"10.1109\/JSTARS.2010.2042280","article-title":"Unsupervised full-polarimetric SAR data segmentation as a tool for classification of agricultural areas","volume":"4","author":"Hoekman","year":"2011","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1607","DOI":"10.5194\/hess-16-1607-2012","article-title":"Estimation of soil parameters over bare agriculture areas from C-band polarimetric SAR data using neural networks","volume":"16","author":"Baghdadi","year":"2012","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2713","DOI":"10.1080\/014311697217297","article-title":"Review article Synthetic aperture radar (SAR) frequency and polarization requirements for applications in ecology, geology, hydrology, and oceanography: A tabular status quo after SIR-C\/X-SAR","volume":"18","author":"Schmullius","year":"1997","journal-title":"Int. J. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1551","DOI":"10.1109\/36.718859","article-title":"Polarimetric SAR interferometry","volume":"36","author":"Cloude","year":"1998","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2583","DOI":"10.1109\/TGRS.2007.897929","article-title":"Fitting a two-component scattering model to polarimetric SAR data from forests","volume":"45","author":"Freeman","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"316391","DOI":"10.1155\/2015\/316391","article-title":"Applications of Polarimetric SAR","volume":"2015","author":"Yang","year":"2015","journal-title":"J. Sens."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"122","DOI":"10.5589\/m04-056","article-title":"Improved ship detection with airborne polarimetric SAR data","volume":"31","author":"Liu","year":"2005","journal-title":"Can. J. Remote Sens."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"442","DOI":"10.1109\/LGRS.2011.2170658","article-title":"Phenomenology of P-band scattering from a tropical forest through three-dimensional SAR tomography","volume":"9","author":"Tebaldini","year":"2012","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"138","DOI":"10.1016\/j.rse.2015.12.037","article-title":"SAR tomography for the retrieval of forest biomass and height: Cross-validation at two tropical forest sites in French Guiana","volume":"175","author":"Rocca","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"967","DOI":"10.1109\/TGRS.2013.2246170","article-title":"Relating P-band synthetic aperture radar tomography to tropical forest biomass","volume":"52","author":"Rocca","year":"2014","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"5294","DOI":"10.1109\/TGRS.2015.2420996","article-title":"Forest height estimation by means of Pol-InSAR data inversion: The role of the vertical wavenumber","volume":"53","author":"Kugler","year":"2015","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Ho Tong Minh, D., Le Toan, T., Tebaldini, S., Rocca, F., and Iannini, L. (2015, January 26\u201331). Assessment of the P-and L-band SAR tomography for the characterization of tropical forests. Proceedings of the 2015 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Milan, Italy.","DOI":"10.1109\/IGARSS.2015.7326429"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Lavalle, M., Hawkins, B., and Hensley, S. (2017, January 23\u201328). Tomographic imaging with UAVSAR: Current status and new results from the 2016 AfriSAR campaign. Proceedings of the 2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Fort Worth, TX, USA.","DOI":"10.1109\/IGARSS.2017.8127498"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"298","DOI":"10.1016\/j.rse.2018.10.025","article-title":"Developing and applying a multi-purpose land cover validation dataset for Africa","volume":"219","author":"Tsendbazar","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_27","unstructured":"White, L.J. (2007). Forest-savanna dynamics and the origins of Marantaceae forest in central Gabon. African Rain Forest Ecology and Conservation, Yale University Press."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Hensley, S., Wheeler, K., Sadowy, G., Jones, C., Shaffer, S., Zebker, H., Miller, T., Heavey, B., Chuang, E., and Chao, R. (2008, January 26\u201330). The UAVSAR instrument: Description and first results. Proceedings of the 2008 IEEE Radar Conference, Rome, Italy.","DOI":"10.1109\/RADAR.2008.4720722"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3481","DOI":"10.1109\/TGRS.2014.2377637","article-title":"UAVSAR polarimetric calibration","volume":"53","author":"Fore","year":"2015","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1775","DOI":"10.1109\/TGRS.2015.2488358","article-title":"Phase calibration of airborne tomographic sar data via phase center double localization","volume":"54","author":"Tebaldini","year":"2016","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"4132","DOI":"10.1109\/TGRS.2009.2023785","article-title":"Algebraic synthesis of forest scenarios from multibaseline PolInSAR data","volume":"47","author":"Tebaldini","year":"2009","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Tebaldini, S., and Rocca, F. (2009, January 4\u20138). On the impact of propagation disturbances on SAR tomography: Analysis and compensation. Proceedings of the 2009 IEEE Radar Conference, Pasadena, CA, USA.","DOI":"10.1109\/RADAR.2009.4976991"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"232","DOI":"10.1109\/TGRS.2011.2159614","article-title":"Multibaseline polarimetric SAR tomography of a boreal forest at P- and L-bands","volume":"50","author":"Tebaldini","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2343","DOI":"10.1109\/TGRS.2010.2091278","article-title":"ALGAE: A fast algebraic estimation of interferogram phase offsets in space-varying geometries","volume":"49","author":"Gatti","year":"2011","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_35","unstructured":"Stoica, P., and Moses, R.L. (2005). Spectral Analysis of Signals, Prentice Hall."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1344","DOI":"10.1109\/TAES.2002.1145755","article-title":"Layover solution in multibaseline SAR interferometry","volume":"38","author":"Gini","year":"2002","journal-title":"IEEE Trans. Aerosp. Electron. Syst."},{"key":"ref_37","first-page":"1","article-title":"The AfriSAR Campaign: Tomographic Analysis With Phase-Screen Correction for P-Band Acquisitions","volume":"99","author":"Wasik","year":"2018","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_38","unstructured":"(2019, February 24). NASA Land, Vegetation, and Ice Sensor (LVIS), AfriSAR Gabon2016 Data Release Oct 2016, Available online: https:\/\/lvis.gsfc.nasa.gov\/datasets\/2016gabon\/LVIS-Gabon-AfriSAR-data-release.pdf."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/5\/475\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:34:46Z","timestamp":1760186086000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/11\/5\/475"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,2,26]]},"references-count":38,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2019,3]]}},"alternative-id":["rs11050475"],"URL":"https:\/\/doi.org\/10.3390\/rs11050475","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2019,2,26]]}}}