星载合成孔径雷达顺轨干涉海流反演研究

发布时间：2018-04-20 03:05

本文选题：海表面流场 + SAR顺轨干涉　；参考：《国家海洋环境预报中心》2017年硕士论文

【摘要】：海流是海洋科学研究中最基本的要素,也是海水的重要运动形式之一。海流研究对海洋减灾、海上搜救、海岸带建设、渔业、航运、污染物扩散等都有重要的研究意义。合成孔径雷达(Synthetic Aperture Radar,SAR)顺轨干涉(Along-Track Interferometric,ATI)具有全天时、全天候、宽测绘带、高分辨率的优点,可以获取大面积、高分辨率、高精度的海洋表面流速信息。一个理想的SAR顺轨干涉系统是进行海流反演的基础,本文以高分三号卫星(GF-3)标准条带模式为例,分析影响SAR顺轨干涉海表面流场测量精度的因素,通过仿真对极化方式、入射角、顺轨干涉有效基线、噪声等效后向散射系数进行了研究,给出了适用于海表面流速测量的理想系统参数,指出高分三号卫星在VV极化、35°~45°入射角、NESZ优于-20dB的情况下适合进行流场测量。针对单星基线过短不能很好的进行流场测量的问题,分析了双星编队模式下理想的顺轨干涉有效基线,结果表明,高分三号卫星在顺轨干涉有效基线范围为28m~56 m时能取得较好的观测结果,仿真结果为后续卫星编队海流监测系统的设计提供了参考。其次,利用GF-3卫星的ATI模式数据对干涉处理获得相位图的过程进行了演示,主要处理步骤包括:SLC数据的读取与显示、利用复相关系数进行主辅图像的配准、将两幅图像进行干涉处理获得干涉相位图、利用圆周期均值滤波对干涉相位图进行降噪处理、分析了获得0.1m/s测速精度所需的多视数并使用多视处理降低相干斑噪声、对缠绕相位进行解缠、对通道不平衡引起的非零干涉相位进行定标、对运动目标引起的方位向偏移进行校正。最后,根据系统参数的分析结果,利用理想的顺轨干涉仿真数据进行一维海表面流场反演,首先对仿真数据进行一系列干涉处理得到可用的干涉相位图,然后基于迭代反演算法进行海流反演,反演误差在0.04m/s左右,验证了算法的可行性。针对目前算法固定步长因子的问题,引入了自适应变步长因子进行改进,分别使用固定步长和变步长因子进行反演,结果表明使用变步长因子可以提高反演精度。
[Abstract]:Current is the most basic element in marine scientific research, and it is also one of the important forms of sea water movement. Current research is of great significance to marine disaster reduction, marine search and rescue, coastal zone construction, fisheries, shipping, pollutant diffusion and so on. Synthetic Aperture radar (SAR) along track interference (Along-Track Interferometric) has the advantages of all-day, all-weather, wide mapping band and high resolution. It can obtain large area, high resolution and high precision information of ocean surface velocity. An ideal SAR along orbit interference system is the basis for ocean current inversion. Taking the GF-3 standard strip model as an example, this paper analyzes the factors that affect the accuracy of the measurement of the current field on the sea surface of the SAR along the orbit interference, and makes a simulation of the polarization mode. The incident angle, the effective baseline of orbit interference, the equivalent backscatter coefficient of noise are studied, and the ideal system parameters for measuring the surface velocity of Yu Hai are given. It is pointed out that the Gaofen 3 satellite is suitable for flow field measurement under the condition that the incidence angle of VV polarization is 35 掳or 45 掳and the incidence angle of NESZ is better than -20 dB. Aiming at the problem that the single satellite baseline is too short to measure the flow field well, the ideal effective baseline of orbit interference in the two-star formation mode is analyzed. The results show that, Gaofen 3 satellite can obtain better observation results when the effective baseline range of orbit interference is 28m~56 m. The simulation results provide a reference for the design of the following satellite formation current monitoring system. Secondly, using the ATI mode data of GF-3 satellite, the process of obtaining phase map by interference processing is demonstrated. The main processing steps include reading and displaying the data of GF-3, and using the complex correlation coefficient to register the main and auxiliary images. The interference phase map is obtained by interferometric processing of two images, and the interference phase map is de-noised by circle periodic mean filter. The multi-view number needed to obtain the accuracy of 0.1m/s velocimetry is analyzed and the speckle noise is reduced by multi-view processing. Unwrapping the winding phase, calibrating the non-zero interference phase caused by channel unbalance, and correcting the azimuth offset caused by moving target. Finally, according to the analysis results of the system parameters, we use the ideal simulation data to retrieve the one-dimensional sea surface current field. Firstly, we use a series of interferometric processing to obtain the available interferometric phase map. Then the current inversion based on iterative inversion algorithm is carried out, and the inversion error is about 0.04m/s, which verifies the feasibility of the algorithm. In order to solve the problem of fixed step size factor, adaptive variable step factor is introduced to improve the inversion accuracy. The variable step size factor and the fixed step size factor are used for inversion, respectively. The results show that the variable step size factor can improve the inversion accuracy.
【学位授予单位】：国家海洋环境预报中心
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P715.6

【参考文献】