Accuracy of differential shift estimation by correlation and split-bandwidth interferometry for wideband and Delta-k SAR systems
Accuracy of differential shift estimation by correlation and split-bandwidth interferometry for wideband and Delta-k SAR systems
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DOI：
10.1109/lgrs.2004.843203
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发表时间：
2005-04-01
影响因子：
4.8
通讯作者：
Eineder, M
中科院分区：
文献类型：
--
作者：
Bamler, R;Eineder, M
估计两幅合成孔径雷达 (SAR) 图像之间图像元素的差异位移是许多应用的基础，例如数字高程模型生成或地面运动测绘。位移测量可以在宏观尺度上以取决于系统距离分辨率的精度明确地进行，或者通过采用干涉测量方法在微观尺度上进行。后者遭受相位循环模糊并且需要相位展开。现代宽带高分辨率 SAR 系统的分辨率小至几十个波长。如果使用足够多的样本进行宏观尺度位移估计，则精度可以提高到分辨率单元的一小部分，甚至可以提高到波长的数量级。然后，精确的绝对测距变得足够精确以支持相位展开甚至使其过时。这封信建立了一些关于偏移估计精度的精度范围的基本方程。适用于多种算法：相干散斑相关、非相干散斑相关、分带干涉测量、多频方法以及杂波中点散射体的相关。结果表明，在各种带宽比下，分带干涉测量的性能接近 Cramer-Rao 界。基于这些发现，建议 Delta-k 系统最好地利用可用的雷达带宽。
Estimation of differential shift of image elements between two synthetic aperture radar (SAR) images is the basis for many applications, like digital elevation model generation or ground motion mapping. The shift measurement can be done nonambiguously on the macro scale at an accuracy depending on the range resolution of the system or on the micro scale by employing interferometric methods. The latter suffers from phase cycle ambiguities and requires phase unwrapping. Modern wideband high-resolution SAR systems boast resolutions as small as a few tens of a wavelength. If sufficiently many samples are used for macro-scale shift estimation, the accuracy can be increased to a small fraction of a resolution cell and even in the order of a wavelength. Then, accurate absolute ranging becomes precise enough to support phase unwrapping or even make it obsolete. This letter establishes a few fundamental equations on the accuracy bounds of shift estimation accuracy. for several algorithms: coherent speckle correlation, incoherent speckle correlation, split-band interferometry, a multifrequency approach, and correlation of point scatterers in clutter. It is shown that the performance of split-band interferometry is close to the Cramer-Rao bound foe a broad variety of bandwidth ratios. Based on these findings, Delta-k systems are proposed to best take advantage of the available radar bandwidth.