Similarity Matching
•Given point sets X and U, compare by finding similarity transformation A that minimizes ||AX-U||.
–X = points X1, …Xn.  U = points U1…Un.
–Find A to minimize sum ||AXi – Ui||^2
–This is just a straightforward, linear problem.
•Taking derivatives with respect to four unknowns of A gives four linear equations in four unknowns.