کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6344882 | 1621213 | 2016 | 11 صفحه PDF | دانلود رایگان |
- AMSPEC-MED automated multi-angular hyperspectral system set in tree-grass ecosystem
- Ecosystem 3-D and FOV ray casting models simulate heterogeneous sensor's observations.
- Diffuse radiation included in Reflectance Distribution Functions (RDF) improves model.
- The model achieves the unmixing of tree and grass hemispherical-directional RDFs.
- Comparison to MODIS BRDF product and hand held spectral data cast r2 â [0.74, 0.88].
The development of tower-mounted automated multi-angular hyperspectral systems has brought new opportunities and challenges for the characterization of the Bidirectional Reflectance Distribution Function (BRDF) on a continuous basis. This study describes the deployment of one of these systems in a Mediterranean savanna ecosystem (AMSPEC-MED), and proposes new approaches for modeling of directional effects. In this study, a Hemispherical-Directional Reflectance Distribution Function (HDRDF) was introduced in order to quantify the effect of diffuse radiation on the estimation of BRDF. The HDRDFs of the two covers of the ecosystem - trees and grasses - were un-mixed using a 3-Dimensional (3-D) model of the observed scene. Up-scaling HDRDF estimates to MODIS BRDF product (r2 â [0.74, 0.86]) and down-scaling to hand held spectral measurements (r2 = 0.88) achieved a reasonable accuracy (RMSE â [1.81, 3.14]). Despite the uncertainties in the estimation of diffuse irradiance and the 3-D representation of the scene, HDRDF un-mixing demonstrates the potential of automated multi-angular proximal sensing to study vegetation properties in heterogeneous ecosystems and the correction of directional effects of different sources.
Journal: Remote Sensing of Environment - Volume 187, 15 December 2016, Pages 447-457