orth.RdRange space or image of a matrix.
orth(M)B=orth(A) returns an orthonormal basis for the range of A.
The columns of B span the same space as the columns of A,
and the columns of B are orthogonal to each other.
The number of columns of B is the rank of A.
Matrix of orthogonal columns, spanning the image of M.
Trefethen, L. N., and D. Bau III. (1997). Numerical Linear Algebra. SIAM, Philadelphia.