R script to calculate NDVI from ASTER images

This R script performs several calculations related to ASTER-based NDVI
in the Kilimanjaro research area. Calculations include mean value,
standard deviation and corresponding coefficient of variation for a
given moving window. Prior to this, single ASTER tiles of bands V2 (red)
and V3N  (near-infrared) are optionally being unzipped and merged, and
the NDVI is derived from these two bands. Calculated indices are being
extracted for each research plot and exported to CSV output file.