<P> Finally, we scale both images to the same approximate resolution and align the now horizontal epipoles for easier horizontal scanning for correspondences (row 4 of 2D image set). </P> <P> Note that it is possible to perform this and similar algorithms without having the camera parameter matrices M and M' . All that is required is a set of seven or more image to image correspondences to compute the fundamental matrices and epipoles . </P> <P> Image rectification in GIS converts images to a standard map coordinate system . This is done by matching ground control points (GCP) in the mapping system to points in the image . These GCPs calculate necessary image transforms . </P> <P> Primary difficulties in the process occur </P>

What do you meant by rectification in gis
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