Wang Xue-qi, Jiao Jian-nan, Yang Bin, Jing Xin, Zhao Hong-ying, Yan Lei
Guang Pu Xue Yu Guang Pu Fen Xi. 2016 Dec;36(12):4094-9.
Polarization is an important characteristic of electromagnetic wave, and using polarization information to study ground features has been proved to be an effective means. Research on ground feature’s polarized properties is an essential part of earth observation. At present, it is in highly need of accurate polarization sensors globally. AirMSPI , (Airborne Multiangle Spectro-Polarimetric Imager) as a new airborne polarized sensor, can obtain multi-band and multi-angle polarization data, and the spatial resolution can reach to ~10 meters. Using the experimental data of Tracy in the year of 2013, this paper analyzes the varying pattern of DOLP (Degree of Linear Polarization) as well as pBRF(polarized Bidirectional Reflectance Factor) in 470 nm, 660 nm, 865 nm bands and 9 view zenith angles. The result shows that, forward scattering of ground features contains plenty of polarized radiation, and ground features present strong non-lambertian effect near principal plane of incidence. DOLP and pBRF has strong correlation to relative position between incidence and view angle. DOLP reaches the maximum value when two directions are perpendicular while pBRF increases with larger view zenith angle. Because of atmospheric effect, radiance of blue band contains most polarized light. However, red and infrared band can attenuate atmospheric molecular polarization scattering effectively, thus contain more polarization details of ground features. Water, artificial structure, residential area, bare soil and vegetation show distinct polarization characteristics, and can be clearly identified. Due to depolarization effect from multi-scattering effect, DOLP and reflected radiation intensity have highly negative correlation, with correlation coefficient generally more than -0.8. AirMSPI sensor can provide high-quality polarization data, as a strong verification to ground-based and satellite-based polarization data, and support parameters inversion of atmosphere and ground features.
偏振是电磁波的一个重要特性，利用偏振信息研究地物已被证明是一种有效的手段。地物偏振特性研究是对地观测的重要组成部分。目前，全球范围内对高精度偏振传感器的需求迫切。机载多角度光谱偏振成像仪（AirMSPI）作为一种新型机载偏振传感器，能够获取多波段、多角度的偏振数据，其空间分辨率可达~10米。本文利用2013年特雷西的实验数据，分析了470纳米、660纳米、865纳米波段以及9个观测天顶角下的线偏振度（DOLP）和偏振双向反射因子（pBRF）的变化规律。结果表明，地物的前向散射包含大量偏振辐射，地物在入射主平面附近呈现出较强的非朗伯效应。DOLP和pBRF与入射角和观测角的相对位置密切相关。当两个方向垂直时，DOLP达到最大值；而pBRF随着观测天顶角的增大而增大。由于大气效应，蓝波段的辐射中包含的偏振光最多。然而，红波段和红外波段能够有效衰减大气分子的偏振散射，从而包含更多地物的偏振细节。水体、人工建筑、居民区、裸土和植被呈现出明显的偏振特征，能够被清晰识别。由于多次散射效应导致的去偏振作用，DOLP与反射辐射强度呈高度负相关，相关系数一般大于-0.8。AirMSPI传感器能够提供高质量的偏振数据，有力地验证了地基和星载偏振数据，并为大气和地物参数反演提供支持。
