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一、理论推导地面目标的辐射率大部分是反射的太阳辐射。在0.4～2.5的μm之间用多光谱扫描仪测得的地面目标的光谱辐射率可由下式计算: L_λ=1/π[(SE_λ(直))/(cosθ)=E_λ(散)]τ(λ)ρ(λ)+L_λ(光) (1) 式中L_λ—测定的光谱辐射率,S—瞬时视场中阴影覆盖系数,θ—地表与太阳到地球中心连线的央角,E_λ(直)—太阳直射目标的光谱辐照度,E_λ(散)—散射光谱辐照度,τ(λ)—大气透射率,ρ(λ)—目标的光谱反射率,L_λ(光)—光潜光路辐照度。在方程(1)中,设目标近似于准朗伯反射体,对所有波长产生双向反射的角度相同。L_λ(光)项代表阳光到达目标之前在检测器与目标之间散射成光束所引起
First, the theoretical derivation of the ground target radiation is mostly reflected solar radiation. The spectral emissivity of the ground target measured with a multi-spectral scanner between 0.4 and 2.5 μm can be calculated as follows: L_λ = 1 / π [(SE_λ (straight)) / (cosθ) = E_λ (λ) ρ (λ) + L_λ (light) where L_λ is the measured spectral emissivity, S is the shadow coverage factor in the S-transient field of view, θ is the central angle connecting the surface and the sun to the center of the Earth, E_λ (Straight) - Spectral irradiance of the direct sun’s target, E_λ (scattered) - Diffuse spectral irradiance, τ (λ) - Atmospheric transmittance, ρ (λ) - Spectral reflectance of the target, L_λ Submerged Road Irradiance. In equation (1), let the target approximate the quasi-Lambertian reflector with the same birefringence at all wavelengths. The L_λ (light) term is caused by the scattering of light between the detector and the target before the sunlight reaches the target