For non-destructive depth profiling by techniques such as PIXE, the effective depth of analysis can be reduced by employing a grazing angle between the incident analysing probe and the sample surface. However, for any given angle of incidence the data obtained is averaged over the depth of penetration. Until now it has not been possible to use observed angle-dependent data to obtain a spectrum from a specific depth below the surface of a sample. In this paper we will present a new generic method to directly determine ‘experimental’ spectra arising from specific depths beneath a surface by the transformation of experimental angle-dependent data. The method is applied to PIXE and demonstrated on spectra from a thin CdS film deposited on glass, the results of which are compared to those obtained from X-ray diffraction.