The locally ordered structure formed by one monolayer of Bi on GaP (110) is studied by x-ray standing wave triangulation applied to three Bragg planes. This system has a larger lattice mismatch than other V/III-V interfaces (e.g., Sb/GaAs, Sb/InP, and Bi/InP), and does not grow epitaxially as those other systems. Prior scanning tunneling microscopy studies of the Bi/GaP interface show that Bi grows in chains along the (110BAR) direction interrupted by vacancies. The large difference in the atomic radii induces the formation of vacancies to allow relaxation. Nevertheless, our results indicate that the interface structure resembles the epitaxial continued layer structure, as in the better matched systems.