Target detection in hyperspectral imagery using demixed spectral angles

We present a modification to the Spectral Angle Mapper (SAM) to perform mixed pixel target detection in hyperspectral imagery. Our method uses the linear mixing model to define a new set of coordinates using endmember spectra. We show that spectral angles measured in this new coordinate system differ from those measured in full band space, and that there is a natural interpretation of angles involving mixed pixels in these new coordinates. We include experimental evidence that our method outperforms traditional SAM in cases involving both subpixel and shaded target situations.