Research on Ground Feature’s Polarized Properties with Multi-Spectral and Multi-Angle AirMSPI Data
WANG Xue-qi, JIAO Jian-nan, YANG Bin, JING Xin, ZHAO Hong-ying, YAN Lei*
Beijing Key Lab of Spatial Information Integration and 3S Engineering Application，School of Earth and Space Science, Peking University, Beijing 100871, China
摘要： 偏振是电磁波的重要特性，利用偏振信息研究地物的状态和性质被证明是一种有效的手段。地物属性研究是地球观测中重要的课题，偏振技术作为一种新兴手段，逐渐得到国内外遥感界的关注。目前，国际上普遍缺乏使用广、精度高的偏振传感器。AirMSPI(Airborne Multiangle Spectro Polarimetric Imager)作为新型机载偏振传感器，能够获取多波段多角度的偏振数据，空间分辨率可达10 m。选取2013年美国Tracy地区的航飞数据，分析了线偏振度(degree of linear polarization，DOLP)与偏振二向反射因子(polarized bidirectional reflectance factor，pBRF)在470，660和865 nm三个波段、九个探测天顶角的变化规律。研究发现，地物前向散射方向包含大量偏振光，其在入射主平面附近表现出强烈的非朗伯体效应。同时，DOLP与pBRF和入射天顶角及探测天顶角的相对位置有关。DOLP在入射及探测天顶角90°夹角附近最大，pBRF随着探测天顶角的增大而增大。受大气影响，蓝光波段的DOLP及pBRF数值相对较高，但红光及近红外波段可有效减弱大气分子偏振散射效应，包含更多地物偏振细节。水体、人工建筑、居民区、裸土和绿地偏振特性迥异，偏振图像中地物甄别度高。且由于分子多次散射的退偏作用，传感器接收到的地物辐射中，线偏振度与反射比具有高度负相关性，相关系数普遍大于-0.8。因此，AirMSPI能够提供高质量偏振数据，作为地面、星载偏振数据的有力验证，为大气及地物参数反演提供重要支持。
关键词：AirMSPI传感器;多波段;多角度;地物偏振
Abstract：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 accuratepolarization sensors globally. AirMSPI , (Airborne Multiangle SpectroPolarimetric 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.
王雪琪，焦健楠，杨 彬，景 欣，赵红颖，晏 磊* . 基于AirMSPI多光谱多角度传感器的地物偏振特性研究 [J]. 光谱学与光谱分析, 2016, 36(12): 4094-4099.
WANG Xue-qi, JIAO Jian-nan, YANG Bin, JING Xin, ZHAO Hong-ying, YAN Lei* . Research on Ground Feature’s Polarized Properties with Multi-Spectral and Multi-Angle AirMSPI Data . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2016, 36(12): 4094-4099.
