摄影测量与遥感技术课件-遥感的物理基础.pptVIP

Mie (米氏)Scatter a = ? Mie scatter exists when the atmospheric particle diameter is essentially equal to the energy wavelengths being sensed. Water vapour and dust particles are major causes of Mie scatter. This type of scatter tends to influence longer wavelengths than Rayleigh scatter. Although Rayleigh scatter tends to dominate under most atmospheric conditions, Mie scatter is significant in slightly overcast ones. Non-selective scatter a ? Non-selective scatter is more of a problem, and occurs when the diameter of the particles causing scatter are much larger than the wavelengths being sensed. Water droplets, that commonly have diameters of between 5 and 100mm, can cause such scatter, and can affect all visible and near - to - mid-IR wavelengths equally. Consequently, this scattering is “non-selective” with respect to wavelength. In the visible wavelengths, equal quantities of blue green and red light are scattered. Non-Selective scatter of EM radiation by a cloud * 传感器探测波段的设计，是通过分析比较地物光谱数据而确定的。 多光谱扫描仪（MSS）的波段设计： MSS1(0.5-0.6 μm) MSS2(0.6-0.7 μm) MSS3(0.7-0.8 μm) MSS4(0.8-1.1 μm) * 同类地物的反射光谱具有相似性，但也有差异性。不同植物；植物病虫害 地物的光谱特性具有时间特性和空间特性。 时间特性 空间特性 * 不同植物光谱曲线比较 * 植被的病虫害 * 时间特征 * 地物发射电磁波的能力以发射率作为衡量标准；地物的发射率是以黑体辐射作为参照标准。 黑体：在任何温度下，对各种波长的电磁辐射的吸收系数等于1（100%）的物体。 黑体辐射(Black Body Radiation )：黑体的热辐射称为黑体辐射。 * 1. Power Source: Blackbody Radiation  Planck’s Law: The amount and spectrum of radiation emitted by a blackbody is uniquely determined by its temperature Max Planck (1858 – 1947) Nobel Prize 1918 Emission from warm bodies peak at short wavelengths wavelength 620 K 380 K * 3、黑体辐射定律 (1)普朗克热辐射定律 表示出了黑体辐射通量密度与温度的关系以及按波长分布的规律。 黑体辐射的三个特性 辐射通量密度随波长连续变化，每条曲线只有一个最大值。 温度越高，辐射通量密度越大，不同温度的曲线不同。 随着温度的升高，辐射最大值所对应的波长向短波方向移动。 * (2)玻耳兹曼定律 Stefan-Boltzmanns law 即黑体总辐射通量随温度的增加而迅速增加，它与温度的四次方成正比。因此，温度的微小变化，就会引起辐射通量密度很大的变化。是红外装置测定温度的理论基础。 温度 300 500 1000 2000 3000 4000 5000 6000 7000 波长 9。66 5。80 2。90 1。45 0。97 0。72 0。