1. A method comprising: providing a reference image and a source image; using a wavelet transformation to produce a transformed reference image and a transformed source image; using the transformed reference image and the transformed source image to estimate affine transform parameters; using the reference image, the source image, and the affine transform estimates to maximize normalized mutual information between the reference image and the source image; and using the normalized mutual information to perform sub-pixel geo-spatial registration of the reference image and the source image to produce an output image.