Fits of 3D finite element method (FEM) simulations to the degree of polarization (DOP) of photoluminescence (PL) measured on facets under SiN stripes on InP substrates are presented. The measured data is low noise and the fits are remarkably good; lobes owing to defects (perhaps dislocations) can be seen in false colour maps of the residues from the least squares fits. It is found that the vast majority (estimated to be > 99%) of the DOP patterns can be attributed to an initial condition for the FEM simulations of biaxial strain in the SiN stripes. In addition to the fits of FEM simulations to the data and discussion of the fits: fits of error functions to PL data to find the resolution of the optical system and the location of the top surface, quantities that are required in fits of 3D FEM simulations to the data, are presented; as is presented some historical information on analysis of luminescent III-V materials and devices by analysis of the DOP of the luminescence, and some information on the dependence of the DOP of luminescence on strain for InP.