Modeling Discrete Forest Anisotropic Reflectance Over a Sloped Surface With an Extended GOMS and SAIL Model

Journal Article · Mon Sep 10 00:00:00 EDT 2018 · IEEE Transactions on Geoscience and Remote Sensing

DOI:https://doi.org/10.1109/TGRS.2018.2863605· OSTI ID:1471234

Wu, Shengbiao ^[1]; Wen, Jianguang ^[2]; Lin, Xingwen ^[1]; Hao, Dalei ^[1]; You, Dongqin ^[3]; Xiao, Qing ^[1]; Liu, Qinhuo ^[2]; Yin, Tiangang ^[4]

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1. Chinese Academy of Sciences, Beijing (China); Univ. of Chinese Academy of Sciences, Beijing (China)
2. Chinese Academy of Sciences, Beijing (China); Univ. of Chinese Academy of Sciences, Beijing (China); Joint Center for Global Change Studies, Beijing (China)
3. Chinese Academy of Sciences, Beijing (China)
4. Singapore-MIT Alliance for Research and Technology (Singapore)

Topographic effects on canopy reflectance play a pivotal role in the retrieval of surface biophysical variables over rugged terrain. In this paper, we proposed a new canopy anisotropic reflectance model for discrete forests, Geometric Optical and Mutual Shadowing and Scattering-from-Arbitrarily-Inclined-Leaves model coupled with Topography (GOSAILT), which considers the effects of slope, aspect, geotropic nature of tree growth, multiple scattering, and diffuse skylight. GOSAILT-simulated areal proportions of four scene components (i.e., sunlit crown, shaded crown, sunlit background, and shaded background) were evaluated using the Geometric Optical model for Sloping Terrains (GOST) model. The canopy reflectances simulated by GOSAILT were validated against two reflectance data sets: Discrete anisotropic radiative transfer (DART) simulations and wide-angle infrared dual-model line/area array scanner (WIDAS) observations. Compared with a horizontal surface, the forest canopy reflectance over a steep slope (60°) is significantly distorted with absolute (relative) bias values of 0.048 (79.60%) and 0.056 (12.02%) for the red and near-infrared (NIR) bands, respectively. The GOSAILT-simulated component areal proportions show close agreements with GOST. Moreover, GOSAILT simulations have high overall accuracy (red band: coefficient of determination (R²) = 0.96; root-mean-square error (RMSE) = 0.003; and mean absolute percentage error (MAPE) = 3.91%; and NIR band: R² = 0.78, RMSE = 0.019; MAPE = 3.94%) when compared with the DART simulations. In conclusion, these extensive validations indicate good performances of GOSAILT in canopy reflectance simulations over sloped surfaces.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1471234
• Journal Information: IEEE Transactions on Geoscience and Remote Sensing, Vol. 57, Issue 2; ISSN 0196-2892
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
canopy reflectance
diffuse skylight (SKYL)
geometric optical (GO)
radiative transfer (RT)
sloped surface