Patent ID: 6356646
Filing Date: 2002-03-12
Classification: G06K,G06T

Abstract:
A method of identifying spectrally-distinctive reflective ground targets, represented by a plurality of pixels in multispectral imagery, comprising the following steps:(a) selecting at least three image bands from a multitude of coregistered multispectral bands, wherein said selected bands consist of a band in the visible, a band in the near-infrared, and a band in the mid-infrared portion of the electromagnetic spectrum; (b) transformation means for correcting said pixels' original values for sensor calibration, solar spectrum characteristics, sensor and illumination geometry, and atmospheric scattering and absorption, thereby resulting in values that closely approximate true reflectance, herein referred to as apparent reflectance values; (c) conversion means for converting plurality of said pixels' apparent reflectance values to ternary percentages, wherein each member of a triad of percentages is the fractional part, of the sum, of one pixels' values from each of said selected bands; (d) plotting indicia on a conventional ternary diagram or triangular plot, wherein each pixel of the plurality of said pixels has an indicium corresponding to said pixel; (e) determining a plurality of spectral-class segment boundaries by visual inspection, from a reference ternary diagram containing plotted points or indicia obtained from a spectral library of reflectors of interest convolved to the bandwidth of the multispectral sensor used, wherein said boundaries are changeable and determined by class-resolution requirements of a classification task; (f) transferring said changeable boundaries to a triangular-shaped, transparent template that is congruent with said ternary diagram; and (g) superimposing said template over said ternary diagram to delineate plurality of said spectral-class boundaries; whereby, the position of the indicia on the ternary diagram, with respect to the plurality of the enclosing boundaries of said superimposed template, constrains the identification of the corresponding image pixels to be members of the spectral class plotted on said reference ternary diagram, within said enclosing boundaries, thus identifying said pixels.