ASIP (version 0.4.9)

arvi: Atmospherically Resistant Vegetation Index

Description

Atmospherically Resistant Vegetation Index (ARVI) is a vegetation based index which minimizes the effects of atmospheric scattering in comparison to NDVI.

Usage

arvi(directory = getwd(), crop = "n", ext2crop = "none", gamma = 1)

Arguments

directory

Path to Satellite image folder. Assign as string (inside double quotes). Either assing inside function or set up satellite image folder as the current working directory before running the function. To define current working directory, either use shortcut key Ctrl+Shift+H or use setwd funtion.

crop

Defines the method of cropping outputs to custom extent.

"n" <- No cropping required (Default).

"u" <- Satellite image will be plotted in the plot window and user can choose the extent by clicking on the top left maximum followed by bottom right maximum.

"y" <- Crop to the maximum and minimum extent of the shapefile.

"f" <- Crop to exact shapefile boundary.

ext2crop

Path to the shapefile (*.shp) which will be used for cropping. Shapefile should have SAME CORDINATE SYSTEM as the satellite image. Either provide the full path of .shp file or provide the name of the shapefile variable which is already opened.

gamma

It is an aerosol dependant factor. For more details please refer Kaufman and Tanre (1992). By default the value is 1.

Value

Computed ARVI product

References

Kaufman, Y. J. and D. Tanre (1992) Atmospherically resistant vegetation index (ARVI) for EOS-MODIS, IEEE Transactions on Geoscience and Remote Sensing, 30 (2). doi:10.1109/36.134076.

Examples

# NOT RUN {
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 <- arvi (directory = path, crop = "y", ext2crop = shapefil)
# }