CCSM: Cross correlogram spectral matching

Cross correlogram spectral matching (CCSM) is a new approach towards mineral mapping from imaging spectrometer data. A cross correlogram is constructed by calculating the cross correlation at different match positions between a test spectrum (i.e., a remotely-sensed spectrum) and a reference spectrum (i.e., a laboratory mineral spectrum). To assess the sensitivity of the cross correlogram as a means of spectral matching, the technique is applied to laboratory spectra. In each experiment, the cross correlogram function was derived, a test of significance of the correlations was conducted and a moment of skewness was calculated to characterize the curve shape of the correlogram. The cross correlogram for a perfect spectral match had a parabolic shape with the maximum correlation of one at match position zero and a symmetry around the central match number. The cross correlation is found to be insensitive to differences in gain and thus allows to compare materials of different albedos. The cross correlogram is relatively insensitive to noise which will reduce the overall correlation but does not affect the shape of the correlogram. Relative small differences in absorption band position and shape between the test and reference spectrum affect the shape, significance and correlation of the correlogram values.