Spectral Unmixing Applied to Desert Soils for the - Naval ...

the Mazourka Canyon OHV park between Owens Valley and Death Valley at the base of
the Inyo Mountains, the approximate coordinates for this site are 36 0 49’ 18”N, 118 0 05’
17”W. A collection of spectra were also taken from the Santa Cruz mountains at
approximately 37 0 07' 26.55"N, 122 0 00' 42.22"W for analysis of how soil reflectance
changes with the same material under different disturbance conditions.
B. METHODS
1. Atmospheric Correction
Atmospheric correction must be performed on the AVIRIS data to remove the
effects of atmospheric absorption and scattering in order to obtain the surface reflectance
of a material for comparison to library spectra (Figure 16). Atmospheric corrections are
applied on a pixel by pixel basis in order to analyze reflectance for materials in specific
regions of the imagery. AVIRIS data were atmospherically corrected using the Fast
Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) method.
Figure 16. In this figure from Birvio et al. (2001) the solar radiation interactions are
illustrated. E0 is solar irradiance at the top of the atmosphere, Ed is diffuse
solar irradiance. Ls represents radiance emitted from the target, Ld is the
atmospheric path radiance and L0 is radiance measured by the sensor. θz and
θv are downward and upward transmittance from the atmosphere,
respectively, and θz and θv represent the solar zenith and sensor viewing
zenith angles, respectively.
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