envi hyperspectral analysis - SAM, SFF

Spectral Angle Mapper (SAM) is a classification method for comparing object spectra to know spectra. SAM is can be used after reflectance image is generated by FLAASH method.

load image and roi

toolbox -> spectral angle map -> select spectral subset to cover absorption feature

import roi from input

set preview region

reduce max angle radians to 0.04

SAM classification result

data manager -> load generated SAM rule file

dark region shows image spectrum is similar to know material

bring classification result to the front of rule file

kaolinite deposit

Buddingtonite deposit

SFF (spectral feature fitting) is a method to find known material location on image. It works well for material with absorption feature.

toolbox -> continuum removal to normalize image

display -> spectral library -> select reference material

toolbox -> spectral feature fitting -> select normalized image -> set spectral subset around absorption

import reference material from plot window

bright region has similar spectrum to reference material

display -> scatter plot -> file -> select band

change x to rms, y to scale. low rms means less error. high scale means more spectrum similarity

circle around on scatter plot to highlight region with low rms and high scale

reference:

https://www.l3harrisgeospatial.com/docs/whole-pixel_hyperspectral_analysis_tutorial.html