Introduction - If you have any usage issues, please Google them yourself
Finding the Nearest Orthonormal Matrix
In some appoaches to photogrammetric problems (perhaps inspired by projective
geometry), an estimate M of an orthonormal matrix R representing rotation is
recovered. It is then desired to find the “nearest’’ orthonormal matrix. While
this two step approach — first finding a “best fit’’ matrix without enforcing orthonormality,and then finding the nearest orthonormal matrix — is not to be
recommended, it may be of interest to find a solution to this problem nevertheless.