Modified soil adjusted vegetation index of the Sarcobatus Flat area of the Death Valley regional flow system, Nevada and California, 1989

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 1989 for Sarcobatus
Flat. 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 1989 for
the Sarcobatus Flat area of 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 1989 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.