Given set of cameras P i {\displaystyle P^{i}} and 3D points X j {\displaystyle X_{j}} reconstructed up to projective ambiguity (using, for example, bundle adjustment method) we wish to define rectifying homography H {\displaystyle H} such that { P j H , H − 1 X J } {\displaystyle \left\{P^{j}H,H^{-1}X_{J}\right\}} is a metric reconstruction. After that internal camera parameters K i {\displaystyle K_{i}} can be easily calculated using camera matrix factorization P M i ≡ P i H = K i ( R i | t i ) {\displaystyle P_{M}^{i}\equiv P^{i}H=K_{i}\left(R_{i}|t_{i}\right)} .