Characterizing Olive Grove Canopies by Means of Ground-Based Hemispherical Photography and Spaceborne RADAR Data

Sensors

Iñigo Molina²  Carmen Morillo²  Eduardo Garc໚-Meléndez¹  Rafael Guadalupe² 

[1] Facultad de Ciencias Biológicas y Ambientales, Area de Geodinámica Externa, Campus de Vegazana, Universidad de León, León 24071, Spain; E-Mail:;ETSITGC, Technical University of Madrid, Campus SUR, Ctra. de Valencia, km.7, Madrid 28031, Spain; E-Mails:

关键词: active remote sensing;    RADARSAT 2;    soil roughness;    soil moisture;    backscattering coefficient;    microwave scattering models;    hemispherical photography;    Gap Fraction;    Leaf Area Index (LAI);   

DOI  :  10.3390/s110807476

来源: mdpi

【 摘 要 】

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 (σ⁰). 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° 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 (LAI_eff) 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.

【 授权许可】

CC BY   
© 2011 by the authors; licensee MDPI, Basel, Switzerland.