RGISTools (version 0.9.7)

varEVI: Calculate the enhanced vegetation index (EVI)

Description

varEVI computes the enhanced vegetation index (EVI) from the blue, near-infrared (NIR) and red bands.

Usage

varEVI(blue, red, nir, scfun = function(r) {     r })

Arguments

blue

a raster with the blue band of the capture.

red

a raster with the red band of the capture.

nir

a raster with the NIR band of the capture.

scfun

a function to re-scale the original pixel values into reflectance (0-1).

Value

An EVI image in raster format.

Details

The enhanced vegetation index (EVI) is a vegetation indicator that improves sensitivity towards high biomass densities compared to NDVI huete2002overviewRGISTools (See varNDVI). This function is used within ls7FolderToVar, ls8FolderToVar, modFolderToVar and senFolderToVar.

References

huete2002overviewRGISTools

Examples

# NOT RUN {
# path to the cropped and cutted MODIS images for the region of Navarre
img.dir <- system.file("ExNavarreVar", package = "RGISTools")
# list all the tif files
img.files <- list.files(img.dir, pattern = "\\.tif$", recursive = TRUE, full.names = TRUE)
# print the MOD09 bands
getRGISToolsOpt("MOD09BANDS")
scale.factor <- 0.0001

# select the red, blue and nir bands
red <- raster(img.files[1]) * scale.factor
blue <- raster(img.files[3]) * scale.factor
nir <- raster(img.files[2]) * scale.factor
# calculate the EVI without scale
evi.1 <- varEVI(blue, red, nir)
# calculate the EVI scaling 0-1
evi.2 <- varEVI(blue, red, nir,scfun=getRGISToolsOpt("MOD09SCL"))
evi.12 <- stack(evi.1,evi.2)
# plot the image
spplot(evi.12,col.regions=rev(terrain.colors(20)),at = c(seq(0,1,0.05)))
# }