将城市主体结构简化为两侧为建筑物中间为道路的街道结构,并假定街道径直走向,在一个像元内为无限长,采用几何 光学的方法分别计算楼房顶部、竖直墙面以及道路对像元辐射值的贡献。从而构建了大尺度下城市主体结构的二向反射率因子(BRF)模 型。在微尺度上考虑了城市结构自身表面的BRF模型,由于在某个城市像元中还可能存在植被,因此模型中还考 虑了植被的BRF模型,从而完成了对城市地区BRF模型的构建。对构建的模型进行模拟计算和敏感性分析,发现城市 地区BRF典型特征是出现了热点效应和镜面反射峰,并且楼房高度和植被覆盖度对城市地区BRF影响显著。

The city main structure was simplified to the street structure in which both sides are buildings and the middle is road. The street structure was assumed straight forward and infinite within a pixel, the contribution of pixel radiance from the top of the buildings, the vertical walls and the road was computed respectively using geometrical optics method. Then the bidirectional reflectance function(BRF) of the main structure of the city was constructed in large scale. In the micro-scale, the BRF of the structure surface itself was considered too. For an urban pixel, there may be vegetation, so the BRF of vegetation was considered in the model and the BRF over urban areas was constructed. The BRF of an urban pixel was calculated and the sensitivity was analyzed, the characteristic of BRF over urban areas is the emergence of specular reflection peak and hot spot, and the height of building and vegetation coverage have significantly effects on the BRF of an urban pixel.