Modified soil adjusted vegetation index for the Death Valley regional flow system, Nevada and California, 1992

The data set was created to determine areas of regional plant-cover
information for use in the report "Ground-water discharge determined from
estimates of evapotranspiration, Death Valley regional flow system, Nevada and
California."

The raster-based Modified Soil Adjusted Vegetation Index was derived from
Landsat Thematic Mapper imagery data acquired during June 1992 for the Death
Valley regional flow system. The index has been shown to increase the dynamic
range of the vegetation signal while further minimizing the soil background
influences, resulting in greater vegetation sensitivity as defined by a
"vegetation signal" to "soil noise" ratio. The data set was used in determining
phreatophyte boundaries for a ground-water evapotranspiration study and
relative differences in vegetation density between discharge areas.

Introduction

The raster-based Modified Soil Adjusted Vegetation Index (MSAVI) was derived
from Landsat Thematic Mapper (TM) imagery data acquired during June 1992 for
the Death Valley regional flow system. Background and formulas of the MSAVI are
detailed in Qi and others (1994).

The MSAVI has been shown to increase the dynamic range of the vegetation signal
while further minimizing the soil background influences, resulting in greater
vegetation sensitivity as defined by a "vegetation signal" to "soil noise"
ratio. The MSAVI is a type of Soil Adjusted Vegetation Index (SAVI). The SAVI
includes a constant soil adjustment factor L. The MSAVI uses the Normalized
Difference Vegetation Index (NDVI) and Weighted Difference Vegetation Index
(WDVI) to compute the L value in the SAVI for each picture element or pixel.
This is referred to as a self-adjusting L function in Qi and others (1994, p.
123). The slope of the soil line used in the equations was 1.06. This was used
by Qi and others (1994, p. 123) and was determined to be an acceptable value
for this study.

Reviews

The MSAVI image for 1992 was checked for consistency and accuracy during the
data processing. Two external reviews were done. The reviewers were asked to
check metadata and other documentation files for completeness and accuracy.
Reviewers also were asked to check the topological consistency, tolerances,
projections, and geographic extent.