Analyses of fluorescent soft X-ray spectra from planetary surfaces obtained by orbiting spacecraft use the intensities of elemental emission lines and their ratios to, e.g., determine the geochemistry of the surface of the target body. Historically, in the analyses it has been assumed that the planetary surfaces can be considered as homogeneous and plane-parallel media. It has been shown, however, that both absolute and relative line intensities are affected by the physical properties of the target surface and the viewing and illumination geometry of observations. Here we present experimental and numerical simulation studies into the effect of regolith on the measured elemental ratios and line intensities as a function of the measurement geometry, and some select results.