人工角反射器辐射特性及其像素级精定位参数

RADIATION CHARACTERISTICS OF ARTIFICIAL CORNER REFLECTORS AND PARAMETERS SELECTION FOR ITS PIXEL LEVEL PRECISION POSITIONING

角反射器精确定位是角反射器微形变获取的前提,文中从研究角反射器影像特征入手,详细介绍了角反射器强度、相关性和光谱离散指数(MSR-Mean to Standard deviation Ratio)影像特征:1)角反射器强度影像特征明显,其影像扩散在多个像素上,Envisat数据中角反射器表现为亮点,而TerraSAR数据中角反射器呈明显的十字型;2)角反射器MSR影像特征不明显;3)不同带宽多视处理后统计得到的角反射器相关性聚焦在一个像素内,而且相关值明显高于周边像素。将角反射器强度、相关性和MSR作为衡量光谱稳定性的参数,对比分析不同参数定位出的角反射器像素位置及其对应的相位信息,结果表明:角反射器强度易受背景干扰,此参数定位角反射器容易产生偏差;角反射器MSR值与背景差别小,不能单独用于角反射器定位;角反射器相关性聚焦性好,相关性参数能准确定位角反射器的像素位置,对应的相位值比其他参数定位得到的相位值相对稳定。

Accurate positioning of corner reflector （CR） is the precondition to monitor the small deformation. CR can be looked as a better point target and it is expected that the energy remains more or less the same when processing different looks with fractional azimuth and range bandwidth. The intensity, the mean to standard deviation ratio （MSR） of energy and the spectral correlation are used to measure the spectral diversity. The paper begins with the performance of CRs, then describes in detail the intensity image, spectral correlation image and MSR image of CRs in two SAR data ： Envisat data and TerraSAR data. Based on these work, we draw the below conclusions： 1）corner reflector is obvious on the intensity image, and its strong reflectance to radar wave tends to be met also by some adjacent pixels. In Envisat data CRs appear as bright targets, and CRs in TerraSAR data show as clear crosses; 2）In MSR image CRs signals are too weak to be easily detected; 3）One advantage of the correlation measure is that it is ＂well focused＂, so in the case of CRs high values, they are typically found only in one pixel, and the correlation value of this pixel is obviously higher than adjacent pixels. Generating the list of coordinates of CRs with the three criteria parameters： high intensity value, high MSR value and high spectral correlation value, respectively, and then analyzing comparatively the CRs＇ pixels location from different criteria parameters and the corresponding phase information, we can get the results as follows： 1）the intensity is susceptible to disturbance from the background environment, and the CRs pixels located by this parameter are offset when their environment is complex; 2） the difference is so small between the CRs＇ MSR value and the background that it can＇t detect the CRs; 3）compared with the CRs＇ phase located with correlation parameter and other parameters, the phase of former is more stable, indicating that correlation parameter can locate the CRs accurately.