1. A method for estimating at least one parameter of interest from a gamma ray spectrum relating to a volume of matter using standard gamma ray spectra from reference samples, wherein there is at least one non-elemental characteristic that is different between the volume and at least one of the reference samples, wherein the non-elemental characteristic difference affects gamma ray interactions, the method comprising: deconvolving a gamma ray spectrum obtained from the analysis volume into a plurality of elemental spectral yields, wherein deconvolution includes compensating for effects of the non-elemental characteristic difference.