Computation of blowing up centers

Given a birational projective morphism of quasi-projective varieties f :Z→X. We want to find the ideal sheaf over X such that the blowing up of X along corresponds to f. In this paper we approach the problem from two directions, solving two subcases. First we present a method that determines when f is the composition of blowing ups along known centers, then by another method, we compute directly from i(Z) PXn.