Abslract-The interference between two radar images, ac-represents the azimuth from the sensor to the focus and wired from approximately the Same location, has a number has heen added to the image description since SAR images " In particular, the literature with euunple acquired from different azimuths are statistically independent.of cohewnt change detection (CCD) and interferometric SAR respectively enable the detection of small For a general collection the grazing angle can be approximated change and the extraction or terrain elevation. In almost all of uses by a POlYnomid in 6 ' given hYthese examples coherent estimates have been formed by spatially averaging the interfered images to ohlain reliable estimates. This paper looks instead at averaging independant lmks that, although more complicated, allow higher resolution coherent products to be formed over larger areas by reducing the constraints on the allowable quadratic phase error that typically limits image size.
The tomographic paradigm argues that the demodulated pulses from a spotlight mode SAR system trace a 2D slice of the 3D Fourier transform of the complex surface reflectivity. This paper derives the phase errors that result from imaging a 3D surface from a non planar collection geometry and shows how correct projection to the true surface can eliminate many of the errors.The response from an ideal scatterer is derived and then approximated to simplify the expression into a manageable and meaningful form and so that insight can be gained into the artifacts produced.The theory indicates that warping an image by distorting the final image to correct for layover doesn't eliminate the second order blurring terms produced by the relief and that both the layover and these blurring affects can be properly eliminated through correct projection to the real ground plane.
This paper describes a new algorithm for registration of synthetic aperture radar (SAR) images. The algorithm is based on cross-correlation in the Radon transform domain, chosen principally because of the prevalence of line-like features in SAR images. The distributed nature of such features, and their persistence in the image independently of "look angle" , make Radon-domain correlation appropriate for the peculiar challenge of SAR image registration. Furthermore, 2D cross-correlation in Radon space may be efficiently implemented as 1D convolution followed by backprojection. To handle local variations caused by terrain elevations and errors in global parameters, we use a coarse-to-fine matching strategy based on a novel multiresolution Radon transform pyramid. This may be efficiently constructed from an initial fine partition of the image into disjoint tiles, using alternating grouping and decimation steps. The whole algorithm is linear in the number of such tiles. Test results demonstrate that the new algorithm performs comparably to pixel-similarity-based registration when the look angle is the same, and much better for pairs with different look angles.
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