2.2.1. Preprocessing

Level 2 ortho-reflectance AVIRIS flight lines were acquired from the Jet Propulsion Lab (JPL) ftp site (https://aviris.jpl.nasa.gov/data/AV\_HyspIRI\_Prep\_Data.html). The flight lines used in this analysis were f131117t01p00r07, f131117t01p00r08, f131117t01p00r09, and f131117t01p00r10, all acquired on 17 November 2013. Before retrieval, the images had been orthorectified. Surface reflectance was retrieved using ATmospheric REMoval program (ATREM; [48]). Images were further manually georeferenced using United States Geological Survey (USGS) 2004 1m digital orthophoto quarter quad (DOQQ) maps (http://nationalmap.gov/viewer.html) as base maps. Images were warped using a first-degree polynomial with nearest neighbor resampling. Images were resampled to a uniform 14.8 m on a side pixel size. The flight lines cover approximately 93% of the Rim Fire burn scar. Wavelengths 365–405 nm, 1325–1420 nm, 1810–2040 nm, and 2450–2500 nm were known to either be associated with atmospheric water absorption features or found to contain significant atmospheric artifacts and a low signal-to-noise ratio from visual inspection; bands within these wavelengths were not considered in further processing, leaving 177 AVIRIS bands for use in the analysis. In addition, flight lines over the same area from 26 June 2013 were used as sources for the spectral library used for the MESMA process. The flight lines used for this purpose were f130626t01p00r13, f130626t01p00r14, and f130626t01p00r15. These flight lines were processed using procedures already described.
