Slide to be inserted before health map in Catskills AVIRIS case study:

An example of spectral mixing in an assessment of hemlock wooly adelgid
in the Catskills.  Spectral mixing produces a coverage that estimates
the species abundance on a per pixel basis.  A threshold is set to 
determine those pixels dominated by hemlock, and health estimates
are then applied to this pixels.

Fig.  Use hemlock abundance from hemlock abundance/health image pair from
lower right corner of Pontius poster.