{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,31]],"date-time":"2025-12-31T17:56:10Z","timestamp":1767203770545,"version":"build-2238731810"},"reference-count":57,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2011,7,28]],"date-time":"2011-07-28T00:00:00Z","timestamp":1311811200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>One of the main strengths of active microwave remote sensing, in relation to frequency, is its capacity to penetrate vegetation canopies and reach the ground surface, so that information can be drawn about the vegetation and hydrological properties of the soil surface. All this information is gathered in the so called backscattering coefficient (s0). The subject of this research have been olive groves canopies, where which types of canopy biophysical variables can be derived by a specific optical sensor and then integrated into microwave scattering models has been investigated. This has been undertaken by means of hemispherical photographs and gap fraction procedures. Then, variables such as effective and true Leaf Area Indices have been estimated. Then, in order to characterize this kind of vegetation canopy, two models based on Radiative Transfer theory have been applied and analyzed. First, a generalized two layer geometry model made up of homogeneous layers of soil and vegetation has been considered. Then, a modified version of the Xu and Steven Water Cloud Model has been assessed integrating the canopy biophysical variables derived by the suggested optical procedure. The backscattering coefficients at various polarized channels have been acquired from RADARSAT 2 (C-band), with 38.5\u00b0 incidence angle at the scene center. For the soil simulation, the best results have been reached using a Dubois scattering model and the VV polarized channel (r2 = 0.88). In turn, when effective LAI (LAIeff) has been taken into account, the parameters of the scattering canopy model are better estimated (r2 = 0.89). Additionally, an inversion procedure of the vegetation microwave model with the adjusted parameters has been undertaken, where the biophysical values of the canopy retrieved by this methodology fit properly with field measured values.<\/jats:p>","DOI":"10.3390\/s110807476","type":"journal-article","created":{"date-parts":[[2011,9,27]],"date-time":"2011-09-27T20:09:10Z","timestamp":1317154150000},"page":"7476-7501","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Characterizing Olive Grove Canopies by Means of Ground-Based Hemispherical Photography and Spaceborne RADAR Data"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6223-6874","authenticated-orcid":false,"given":"I\u00f1igo","family":"Molina","sequence":"first","affiliation":[{"name":"ETSITGC, Technical University of Madrid, Campus SUR, Ctra. de Valencia, km.7, Madrid 28031, Spain"}]},{"given":"Carmen","family":"Morillo","sequence":"additional","affiliation":[{"name":"ETSITGC, Technical University of Madrid, Campus SUR, Ctra. de Valencia, km.7, Madrid 28031, Spain"}]},{"given":"Eduardo","family":"Garc\u00eda-Mel\u00e9ndez","sequence":"additional","affiliation":[{"name":"Facultad de Ciencias Biol\u00f3gicas y Ambientales, Area de Geodin\u00e1mica Externa, Campus de Vegazana, Universidad de Le\u00f3n, Le\u00f3n 24071, Spain"}]},{"given":"Rafael","family":"Guadalupe","sequence":"additional","affiliation":[{"name":"ETSITGC, Technical University of Madrid, Campus SUR, Ctra. de Valencia, km.7, Madrid 28031, Spain"}]},{"given":"Maria Isabel","family":"Roman","sequence":"additional","affiliation":[{"name":"ETSITGC, Technical University of Madrid, Campus SUR, Ctra. de Valencia, km.7, Madrid 28031, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2011,7,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1051\/agro:2003047","article-title":"Constructing a water-use model for input to the water cloud backscatter model","volume":"23","author":"Graham","year":"2003","journal-title":"Agronomie"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"805","DOI":"10.5589\/m04-043","article-title":"Estimating soil moisture at the watershed scale with satellite-based radar and land surface models","volume":"30","author":"Moran","year":"2004","journal-title":"Can. J. Remote Sens"},{"key":"ref_3","unstructured":"Guyenne, T-D, and Danesy, D (1997, January 14\u201321). ERS-1 SAR Sensitivity to Hydrological Parameters: A Comparison with SIR-C and AIRSAR Data. Florence, Italy."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"370","DOI":"10.1109\/36.134086","article-title":"An empirical model and an inversion technique for radar scattering from bare soil surfaces","volume":"30","author":"Oh","year":"1992","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_5","unstructured":"Ulaby, FT, Moore, RK, and Fung, AK (1986). Microwave Remote Sensing: Active and Passive Volume III: From Theory to Applications, Artech House."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"727","DOI":"10.1109\/TGRS.2003.810702","article-title":"Inversion of surface parameters from polarimetric SAR","volume":"41","author":"Hajnsek","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_7","unstructured":"Oh, Y, Sarabandi, K, and Ulaby, FT (1994, January 8\u201312). An Inversion Algorithm for Retrieving Soil Moisture and Surface Roughness from Polarimetric Radar Observation. Pasadena, CA, USA."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"915","DOI":"10.1109\/36.406677","article-title":"Measuring soil moisture with imaging radars","volume":"33","author":"Dubois","year":"1995","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1109\/36.158872","article-title":"A microwave scattering model for layered vegetation","volume":"30","author":"Karam","year":"1992","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"372","DOI":"10.1109\/TGRS.1995.8746018","article-title":"A three-dimensional radar backscatter model of forest canopies","volume":"33","author":"Sun","year":"1995","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_11","unstructured":"Ulaby, FT, McDonald, K, Sarabandi, K, and Dobson, MC (1988, January 12\u201316). Michigan Microwave Canopy Scattering Model. Edinburgh, UK."},{"key":"ref_12","unstructured":"Guyenne, TD, and Hunt, JJ (1988, January 18\u201322). Retrieving Vegetation and Soil Parameters from Radar Measurements. Aussois, France."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/S0034-4257(97)00129-6","article-title":"Inclusion of a simple multiple scattering model into a microwave canopy backscatter model","volume":"63","author":"Wang","year":"1998","journal-title":"Remote Sens. Environ"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1029\/RS013i002p00357","article-title":"Vegetation modeled as a water cloud for radar sensing of crops","volume":"13","author":"Attema","year":"1978","journal-title":"Radio Sci"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1016\/j.asr.2006.02.032","article-title":"Inferring the effect of plant and soil variables on C- and L-band SAR backscatter over agricultural fields, based on model analysis","volume":"39","author":"Inoueb","year":"2007","journal-title":"Adv. Space Res"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"873","DOI":"10.1109\/36.917914","article-title":"The relationship between the backscattering coefficient and the biomass of narrow and broad leaf crops","volume":"39","author":"Macelloni","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/0034-4257(93)90053-Z","article-title":"Estimating surface soil moisture and leaf area index of a wheat canopy using a dual-frequency (C and X bands) scatterometer","volume":"46","author":"Champion","year":"1993","journal-title":"Remote Sens. Environ"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1016\/S0034-4257(98)00079-0","article-title":"An agroecological modeling approach to explain ERS SAR radar backscatter of agricultural crops","volume":"67","author":"Bouman","year":"1999","journal-title":"Remote Sens. Environ"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1109\/36.285188","article-title":"Adaptation of the MIMICS backscattering model to the agriculturalcontext-wheat and canola at L and C bands","volume":"32","author":"Toure","year":"1994","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/0034-4257(84)90010-5","article-title":"Relating the microwave backscattering to leaf area index","volume":"14","author":"Ulaby","year":"1984","journal-title":"Remote Sens. Environ"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1016\/S0034-4257(99)00065-6","article-title":"Multifrequency soil moisture inversion from SAR measurements with the use of IEM","volume":"71","author":"Bindlish","year":"2000","journal-title":"Remote Sens. Environ"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"596","DOI":"10.1007\/s00468-004-0352-9","article-title":"Competition-dependent modeling of foliage biomass in forest stands","volume":"18","author":"Grote","year":"2004","journal-title":"Trees Struct. Funct"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"453","DOI":"10.1093\/forestry\/cpl030","article-title":"Assessment of allometric algorithms for estimating leaf biomass, leaf area index and litter fall in different-aged Sitka spruce forests","volume":"79","author":"Tobin","year":"2006","journal-title":"Forestry"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2597","DOI":"10.1080\/014311699211958","article-title":"The SIR-C\/X-SAR experiment on Montespertoli: Sensitivity to hydrological parameters","volume":"20","author":"Macelloni","year":"1999","journal-title":"Int. J. Remote Sens"},{"key":"ref_25","first-page":"957","article-title":"Measurement and behavior of dual-polarization vegetation optical depth and single scattering albedo at 1.4- and 5-GHz microwave frequencies","volume":"4","author":"Owe","year":"1996","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"299","DOI":"10.2307\/1941935","article-title":"Remote estimation of crown size, stand density, and biomass on the Oregon transect","volume":"4","author":"Wu","year":"1994","journal-title":"Ecol. Appl"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/j.agrformet.2003.08.027","article-title":"Review of methods for in situ leaf area index determination: Part I. Theories, sensors and hemispherical photography","volume":"121","author":"Jonckheere","year":"2004","journal-title":"Agr. Forest. Meteorol"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"37","DOI":"10.1016\/j.agrformet.2003.08.001","article-title":"Review of methods for in situ leaf area index (LAI) determination, Part II: Estimation of LAI, errors and sampling","volume":"121","author":"Weiss","year":"2004","journal-title":"Agr. Forest. Meteorol"},{"key":"ref_29","first-page":"5","article-title":"Estimaci\u00f3n de par\u00e1metros biof\u00edsicos de vegetaci\u00f3n utilizando el m\u00e9todo de la c\u00e1mara hemisf\u00e9rica","volume":"26","year":"2006","journal-title":"Rev. Teledetec"},{"key":"ref_30","unstructured":"Gonsamo Gosa, A, Schaepman-Strub, G, Kooistra, L, and Pellikka, P (2007, January 23\u201325). Estimation of Leaf Area Index Using Optical Field Intruments And Imaging Spectroscopy. Bruges, Belgiu."},{"key":"ref_31","first-page":"141","article-title":"La huella ecol\u00f3gica del cultivo del olivo en Espa\u00f1a y su aplicabilidad como indicador de agricultura sostenible","volume":"39","author":"Sarria","year":"2004","journal-title":"Papeles Geogr"},{"key":"ref_32","unstructured":"Coppo, P, Ferrazzoli, P, Luzi, G, Paloscia, S, Schiavon, G, and Susini, C (1992, January 26\u201329). MAC-91 on Montespertoli-Preliminary Analysis of Multifrequency SAR Sensitivity to Soil and Vegetation Parameters Multisensor Airborne Campaign. Houston, TX, USA."},{"key":"ref_33","unstructured":"Ferrazzoli, P, Guerriero, L, Paloscia, S, and Pampaloni, P (1994, January 11\u201315). Scattering Properties of Olive Yards and Forests: Experimental Results and Model Simulations. Noordwijk, The Netherlands."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1109\/TGRS.1985.289498","article-title":"Microwave dielectric behavior of wet soil - Part II: Dielectric mixing models","volume":"23","author":"Dobson","year":"1985","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_35","unstructured":"CAN-EYE. Definitions and theoretical background. INRA\u2014Institut National de la Recherche Agronomique, France. Available online: https:\/\/www4.paca.inra.fr\/can-eye\/ (accessed on 18 July 2011)."},{"key":"ref_36","unstructured":"Duthoit, S (Prise en Compte de L\u2019agregation des Cultures Dans la Simulation du Transfert Radiatif: Importance Pour L\u2019Estimation de L\u2019indice Foliaire (LAI), de la Parcelle au Paysage, 2006). Prise en Compte de L\u2019agregation des Cultures Dans la Simulation du Transfert Radiatif: Importance Pour L\u2019Estimation de L\u2019indice Foliaire (LAI), de la Parcelle au Paysage, Ph.D. Thesis, Ecole 'Science de l\u2019Univers, de l\u2019Environnement et de l\u2019Espace', Universit\u00e9 Toulouse III, Toulouse, France."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2470","DOI":"10.1109\/TGRS.2005.853926","article-title":"Radiative transfer model for microwave bistatic scattering from forest canopies","volume":"43","author":"Liang","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1032","DOI":"10.1109\/36.602545","article-title":"Coherent effects in microwave backscattering models for forest canopies","volume":"35","author":"Saatchi","year":"1997","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/0034-4257(86)90068-4","article-title":"Regression models for vegetation radar-backscattering and radiometric emission","volume":"19","author":"Eom","year":"1986","journal-title":"Remote Sens. Environ"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"114","DOI":"10.1016\/j.rse.2005.10.003","article-title":"3D Modelling of forest canopy structure for remote sensing simulations in the optical and microwave domains","volume":"100","author":"Disney","year":"2006","journal-title":"Remote Sens Environ"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1720","DOI":"10.1109\/TGRS.2004.831229","article-title":"Radiative transfer modeling of cross-polarized backscatter from a pine forest using the discrete ordinate and eigenvalue method","volume":"42","author":"Picard","year":"2004","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_42","unstructured":"Sikdar, M, and Cumming, I (2004, January 20\u201324). A Modified Empirical Model for Soil Moisture Estimation in Vegetated Areas using SAR Data. Anchorage, AK, USA."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1109\/TGRS.1986.289585","article-title":"Active microwave soil moisture research","volume":"GE-24","author":"Dobson","year":"1986","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"129","DOI":"10.1016\/S0034-4257(00)00200-5","article-title":"Parameterization of vegetation backscatter in radar-based, soil moisture estimation","volume":"76","author":"Bindlish","year":"2001","journal-title":"Remote Sens. Environ"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1016\/S0022-1694(96)03166-6","article-title":"Retrieval of soil moisture and vegetation characteristics by use of ERS-1 wind scatterometer over arid and semi-arid areas","volume":"188","author":"Magagi","year":"1997","journal-title":"J. Hydrol"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"3401","DOI":"10.1080\/01431169608949158","article-title":"Monitoring leaf area of sugar beet using ERS-1 SAR data","volume":"17","author":"Xu","year":"1996","journal-title":"Int. J. Remote Sens"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1111\/j.1469-8137.1960.tb06195.x","article-title":"Inclined point quadrats","volume":"59","author":"Wilson","year":"1960","journal-title":"New Phytol"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/0168-1923(94)02175-J","article-title":"Non-destructive measurement of leaf area in olive (Olea europaea L.) trees using a gap inversion method","volume":"73","author":"Villalobos","year":"1995","journal-title":"Agr. Forest. Meteorol"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"491","DOI":"10.1051\/forest:2007026","article-title":"Stand biometry and leaf area distribution in an old olive grove at Andria, southern Italy","volume":"64","author":"Jones","year":"2007","journal-title":"Ann. For. Sci"},{"key":"ref_50","unstructured":"Rijckenberg, G, van den Broek, A, and Lemoine, G (1995, January 10\u201314). On the Influence of Vegetation and Soil in Microwave Backscatter from Vegetated Surfaces. Firenze, Italy."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"341","DOI":"10.1109\/TGRS.1995.8746015","article-title":"A theoretical analysis of the effect of forest structure on synthetic aperture radar backscatter and the remote sensing of biomass","volume":"33\u20132","author":"Imhoff","year":"1995","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1041","DOI":"10.1109\/36.312892","article-title":"Backscattering properties of boreal forests at the C-and X-bands","volume":"32","author":"Pulliainen","year":"1994","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"4197","DOI":"10.1080\/01431160110107725","article-title":"On the influence of canopy structure on the radar backscattering of mangrove forests","volume":"23","author":"Proisy","year":"2002","journal-title":"Int. J. Remote Sensi"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1726","DOI":"10.1109\/TGRS.2006.887002","article-title":"Estimation of forest fuel load from radar remote sensing","volume":"45","author":"Saatchi","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens"},{"key":"ref_55","first-page":"155","article-title":"The physiology of adaptation and yield expression in olive","volume":"31","author":"Connor","year":"2005","journal-title":"Hortic. Rev"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1007\/s00271-005-0011-y","article-title":"Water requirements of olive orchards: Simulation of daily evapotranspiration for scenario analysis","volume":"24","author":"Testi","year":"2006","journal-title":"Irrig. Sci"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/S0378-3774(00)00116-5","article-title":"Rainfall interception by olive trees in relation to leaf area","volume":"49","author":"Giraldez","year":"2001","journal-title":"Agric. Water Manag"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/11\/8\/7476\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:56:54Z","timestamp":1760219814000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/11\/8\/7476"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2011,7,28]]},"references-count":57,"aliases":["10.3390\/s100807476"],"journal-issue":{"issue":"8","published-online":{"date-parts":[[2011,8]]}},"alternative-id":["s110807476"],"URL":"https:\/\/doi.org\/10.3390\/s110807476","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2011,7,28]]}}}