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Automatic image registration based on correlation and Hough transform

Automatic image registration is a process related to various application fields such as remote sensing, medicine, computer vision, among others. Particularly in remote sensing, the ever increasing number of available satellite images asks for automatic image registration methods, capable of correctly align a new image. An automatic image registration method is proposed, based on the identification of a thin line through the Hough transform, from the diagonal brighter strip visible on the correlation images. This procedure is applied for both directions. Dividing an image into tiles and taking the center of each tile as a point, a geometric correction at the subpixel level may be achieved. Measures for an objective assessment of the geometric correction quality are also proposed, as a complement to the traditional RMS of the errors and visual inspection. An orthorectified Landsat image and an ASTER image with an approximate geometric correction were used. The images were superimposed and resampled. An image registration with subpixel accuracy was achieved. The proposed methodology has showed to be able to correctly align two images, having a priori a "gold standard" image covering a considerable part of the image to be registered.