Using blocks of skewers for faster computation of Pixel Purity Index

摘要

The "pixel purity index" (PPI) algorithm proposed by Boardman, et al.~1 identifies potential endmember pixels in multipsectral imagery. THe algorithm generates a large number of "skewers" (unit vectors in random directions), and then computes the dot product of each skewer with each pixel. The PPI is incremented for those pixels associated with the extreme values of the dot products. A small number of pixels (a subset of those with the largest PPI values) are selected as "pure" and the rest of the pixels in the image are expressed as linear mixtures of these pure endmembers. This provides a convenient and physically-motivated decomposit ion of the image in terms of a relatively few components.