  Let P(S) be the space of convex projective structures on a surface S with
negative Euler characteristic. Goldman and Bonahon-Dreyer constructed two
different sets of global coordinates for P(S), both associated to a pair of
pants decomposition of the surface S. The article explicitly describes the
coordinate change between these two parametrizations. Most of the arguments are
concentrated in the case where S is a pair of pants, in which case the
Bonahon-Dreyer coordinates are actually due to Fock-Goncharov.
