LSRS (version 0.2.0)

Soil-Adjusted Vegetation Index: Soil-Adjusted Vegetation Index

Description

In areas where vegetative cover is low (i.e., < 40 percent) and the soil surface is exposed, the reflectance of light in the red and near -infrared spectra can influence vegetation index values. This is especially problematic when comparisons are being made across different soil types that may reflect different amounts of light in the red and near infrared wavelengths (i.e., soils with different brightness values). The soil -adjusted vegetation index was developed as a modification of the Normalize d Difference Vegetation Index to correct for the influence of soil brightness when vegetative cover is low. The SAVI is structured similar to the NDVI but with the addition of a <U+201C>soil brightness correction factor,<U+201D>

SAVI=(NIR-Red)/(NIR+Red+L)*(1+L)

The SAVI is structured similar to the NDVI but with the addition of a <U+201C>soil brightness correction factor,<U+201D> where NIR is the reflectance value of the near infrared band, RED is reflectance of the red band, and L is the soil brightness correction factor. The value of L varies by the amount or cover of green vegetation: in very high vegetation regions, L=0; and in areas with no green vegetation, L=1. Generally, an L=0.5 works well in most situations and is the default value used. When L=0, then SAVI = NDVI.

Usage

SAVI(a="NIR",b="Red")

Arguments

a

NIR satellite band (format:TIF)

b

Red satellite band (format:TIF)

References

[1] http://wiki.landscapetoolbox.org/doku.php/remote_sensing_methods:soil-adjusted_vegetation_index.

Examples

# NOT RUN {
## The function is currently defined as
function (a="NIR",b="Red")
{
name <- SAVI(a,b)
areaXY <-c(xmin, xmax, ymin, ymax)
cropXY <- crop(name, areaXY)
plot(cropXY,lwd=4,
     main="SAVI",
     xlab="easting", ylab="northing")
hist(cropXY,
     main="SAVI"
     ,
     xlab="SAVI",col="red", ylab="Frequency of Pixels")
  }
# }