gemi {ASIP}

R Documentation

Global Environmental Monitoring Index

Description

Global Environmental Monitoring Index (GEMI) is a vegetation based index designed to reduce the effects of atmosperic effects.

Usage

gemi(directory = getwd(), crop = "n", ext2crop = "none")

Arguments

ext2crop, crop, directory

Same as mentioned in arvi.

Value

Computed GEMI product

Note

1. GEMI = n (1 - 0.25n) - ((r_red - 0.125)/(1 - r_red))

where, n= (2 (r_nir^2 - r_red^2) + 1.5 r_nir + 0.5 r_red)/ (r_nir + r_red + 0.5) and "r_" denotes TOA reflectance band.

Other important notes are mentioned in custom.eqn.

References

Pinty, B. and M. M. Verstraete (1992) GEMI: a non-linear index to monitor global vegetation from satellites, Vegetatio, 101 (1), 15-20.

Examples

library (raster)
library (rgdal)
# Finding the path of the sample satellite image directory.
# User may define paths directly like "/home/ur_folder" or "C:/ur_folder"
path <- system.file ("TM_sample", package = "ASIP")
shapefil <- paste0 (path, "/test.shp")
op <- gemi (directory = path, crop = "y", ext2crop = shapefil)

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