| 模型ID： | M00025 | ||||||
| 模型名称： | 几何光学模型 | ||||||
| 模型编码者： |
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| 模型关键字： | 森林、冠层结构、相互荫蔽、四分量 | ||||||
| 模型类型： | 理论模型 | ||||||
| 模型最后修改日期： | 2014/4/19 0:00:00 | ||||||
| 模型提交日期： | 2014/4/19 0:00:00 | ||||||
| 模型摘要： | GOMS模型是在Li- Strahler几何光学模型的基础上，进一步解决了树冠间相互荫蔽的问题，使几何光学模型适用于较高郁闭度的森林。模型假定遥感像元尺度植被冠层的BRDF特性可以用几何光学原理解释，是由于像元内不连续三维几何体被不同方向照射和观测造成的。假定传感器接收像元视场A内的方向反射信号只有两种不同的值：地面和树冠的反射。考虑到冠层的三维结构参数、天空光和多次散射，得出遥感接收的信号为4个分量的面积加权和. | ||||||
| 公式： |
| 1 |
名称：冠层结构参数nR2
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参数类型：double
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物理意义：表征垂直方向上树冠覆盖度的情况
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| 2 |
名称：冠层结构参数b/R
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参数类型：double
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物理意义：描述树冠形状
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| 3 |
名称：冠层结构参数h/b
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参数类型：double
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物理意义：描述树冠离地面高度和树冠垂直高度的比例
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| 4 |
名称：冠层结构参数Δh/b
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参数类型：double
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物理意义：描述像元内树冠高度空间分布的离散度
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| 5 |
名称：直照地面反射率
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参数类型：double
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物理意义：表征地面反射强度
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| 6 |
名称：直照树冠反射率
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参数类型：double
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物理意义：表征树冠反射率
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| 7 |
名称：阴影反射率
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参数类型：double
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物理意义：阴影反射强度
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| 8 |
名称：太阳天顶角
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参数类型：double
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物理意义：描述太阳位置
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| 9 |
名称：太阳方位角
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参数类型：double
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物理意义：描述太阳位置
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| 10 |
名称：观测天顶角
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参数类型：double
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物理意义：描述观测位置
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| 11 |
名称：观测方位角
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参数类型：double
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物理意义：描述观测位置
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| 12 |
名称：反射率
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参数类型：double
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物理意义：计算结果
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| 标题： | Geometric-optical bidirectional reflectance modeling of the discrete crown vegetation canopy: effect of crown shape and mutual shadowing | |||||||||
| 文献作者： |
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| 文献引用： | Geoscience and Remote Sensing, IEEE Transactions on | |||||||||
| 文献摘要: | In the case where a vegetation cover can be regarded as a collection of individual, discrete plant crowns (such as forest, woodland, savanna, or shrubland), the geometric-optical effects of the shadows that the crowns cast on the background and on one another strongly condition the brightness of the vegetation cover as seen from a given viewpoint in the hemisphere. At the "hotspot," when illumination and viewing positions coincide, shadows are hidden behind plant crowns and the scene appears bright. As the viewing position diverges from that of illumination, the shadows behind the crowns are progressively revealed and the scene darkens. Because, in general, the shadows will not be circular, the amount of shadow revealed will be a function of both the zenith and azimuth angles by which the viewing and illumination positions diverge, rather than a simple phase angle between them. This effect creates an assymetric hotspot, in which the shape of the hotspot is related to the shape of the plant crowns in the scene. At large zenith angles, mutual shadowing of crowns becomes an important factor. Illumination shadows will tend to fall on other crowns, rather than the background, and will preferentially shadow the lower portions of adjacent crowns. Further, these shadows will be preferentially obscured since adjacent crowns will also tend to obscure the lower portions of other crowns. This effect produces a "bowl-shaped" BRDF in which the scene brightness increases at the function's edges. Our paper derives formulas describing the hotspot and mutual-shadowing effects and presents examples that show how the shape of the BRDF is dependent on the shape of the crowns, their density, their brightness relative to the background, and the thickness of the layer throughout which the crown centers are distributed. |
模型公式