SPECPR Users’ Manual Page 8-f45.1 F45: Automatic Band Analysis Alias = aba This routine uses the segmented upper hull (see f44) to isolate absorption features in a spectrum and then for each feature the following are derived: Band Center Full Width at Half Maximum (FWHM) Band Depth Error in band depth (assuming that error bars were included with the input spectrum) Full Width at Quarter Maximum (FWQM) Band Asymmetry Continuum reflectance level Segmented Upper Hull iteration number
The output is a data set using 9 channels to describe each feature (the 8 items above and one additional that is currently unused). Thus if the input spectrum contained 26 features, then the output data set would have 234 channels. This routine was used to generate the features in the USGS Digital Spectral Library. For a description of the continuum algorithm, see Clark, R.N., T.V.V. King, and N.S. Gorelick, Automatic Continuum Analysis of Reflectance Spectra: Proceedings of the Third Airborne Imaging Spectrometer Data Analysis Workshop, JPL Publication 87-30, 138-142, 1987. Once the continuum is removed, the band center is found by finding the lowest channel in a feature and fitting a parabola to the lowest channel and the channel in each side of the lowest one. The FWHM, and FWQM are found by linear interpolation. The error bar is found based on the error bars on the data. The asymmetry is found by ratioing the distance from the band center to each FWHM point. See also section 9.8, Interactive Band Analysis (it uses the same algorithms).