Expansion of Centered Triangulations

We use a construction of A. Bouchet for covering triangulations by means of nowhere-zero dual flows, but slightly modified, to prove that whenever G is a simple graph, which is not a star, two-cell embedded in a surface S, and m is a non-negative integer not divisible by 2, 3, or 5, there is a covering two-cell embedding of G(m) in a surface S̃, orientable if and only if S is orientable, such that each face of the embedding of G and the faces above it in the embedding of G(m) have the same length.