Unveiling the lithology of vegetated terrains in remotely sensed imagery

"Forced invariance" is a processing method that can subdue the expression o f vegetation and enhance the expression of the underlying lithology in remo tely sensed imagery. Data for each spectral band are altered in an empirica lly derived manner so as to produce a refined band that largely excludes co ntrasts attributable to variations in vegetation abundance. This is accompl ished by (1) correcting the data for the effects of additive path radiance, (2) statistically characterizing the relationship between the band data an d a vegetation index, and (3) multiplying the band data as a function of th e index so that the average band value is generally invariant across all in dex values. Comparison of original and processed color composite displays c onfirms the method's utility in unveiling rock patterns consistent with nea rby well-exposed bedrock and alluvial patterns downslope, especially in are as of open canopy vegetation such as in mixed and and semi-arid terrains.