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利用遥感手段监测水质污染具有监测范围广、实时性强的优点。本研究选择中国南方地区水质变化明显的河流区域作为研究对象,利用C波段星载极化合成孔径雷达(极化SAR)卫星RADARSAT-2提供的数据,对基于极化SAR的河流水质污染监测技术进行了初步研究。首先介绍了电磁波的极化现象以及极化SAR的基本原理;其次结合一次同步测量实验,提取河流区域,并对极化SAR数据与水质常见监测指标的监测数据进行对比分析,通过对10个采样点18组数据的分析发现,极化相干矩阵中的T22元素与部分水质指标(如五日生化需氧量BOD5等)具有较强的相关性,从而反映水质的污染状况;并通过实测数据和最小二乘法,拟合得到了利用[T]矩阵元素反演BOD5的经验公式,拟合系数达到0.82。最后通过对地表散射模型和菲涅尔系数的分析,从理论上探讨了极化相干矩阵中部分元素与水体物理性质存在相关性的原因。初步理论分析和实验数据表明,T22元素能够反映水体的污染状况。
Using remote sensing to monitor water pollution has the advantages of wide monitoring range and real-time performance. In this study, the river area with obvious water quality changes in southern China was selected as the research object. Based on the data provided by RADARSAT-2, a C-band space-borne synthetic aperture radar (Polarization SAR) satellite, Conducted a preliminary study. Firstly, the polarization phenomenon of electromagnetic wave and the basic principle of polarization SAR are introduced. Secondly, a simultaneous measurement experiment is taken to extract the river area and the comparative analysis of the monitoring data of the polarization SAR data and water quality monitoring indicators. By comparing 10 samples Point 18 data analysis found that the T22 element in the polarization coherence matrix and some water quality indicators (such as BOD5 on the 5th biochemical oxygen demand, etc.) have a strong correlation to reflect the quality of water pollution; and measured data and Least square method, the empirical formula of BOD5 inversion using [T] matrix elements is obtained, and the fitting coefficient reaches 0.82. Finally, by analyzing the surface scattering model and the Fresnel coefficient, the reason why some elements in the polarization coherence matrix are related to the physical properties of water body is theoretically discussed. Preliminary theoretical analysis and experimental data show that the T22 element can reflect the water pollution.