ndvi: Calculate NDVI from raster.

In DGampe/TriangleMethod: Calculation of NDVI, LST and finally provide an estimation for actual evapotranspiration patterns using remote sensing data (default LANDSAT TM and ETM+ scenes).

Calculate NDVI from raster.

Description

This function will calculate the Normalized Difference Vegetation Index from raster data sets - either in memory, or as files (which will be rastered), defined as:

NDVI = (NIR - RED) / (NIR + RED)

The NDVI will be calculated from pure DN as default, however, an option to caculate the NDVI based on reflectance is implemented according to the procedure by Chander et al. (2009). See argument 'calc.ref' for more information.

Usage

  ndvi(NIR,RED, ...)

Arguments

NIR	File containing the NIR information for calculation.
RED	File containing the RED information for calculation.
write	Specify, if the resulting NDVI grid should be written to file.Default = F (T/F)
outpath	User defined outpath to write the final NDVI file.
outname	User defined name for the resulting file.(Default name / format: 'ndvi.tif'
calc.ref	Should the NDVI be calculated from reflectance? Default = FALSE, NDVI will be calculated from DN only. If set TRUE, make sure to provide the date of the scene. See date for further information.
sensor	Sensor for NDVI calculation. Default "tm", other option: "etm+". Only important if calc.ref = TRUE.
Date	Date of the scene (overpassing date). Format POSIXct, e.g. "1990-01-10". Default is "1990-01-01". Only important if calc.ref = TRUE.
Lmin.red,...	Calibration parameter files for the sensor. Landsat TM and ETM+ are implemented, if images originate from a different sensor, these parameters should be adjusted. Only relevant if calc.ref =T.

Details

Note: calculation of the NDVI for a larger scene (e.g. one entire Landsat image) will require a lot of time and memory! If only a smaller part of the image is needed, consider to crop the image first. Conversion to reflectance according to Chander et al. (2009).

Value

RasterLayer .tiff file

Examples

  NIR<- raster(ncol=30,nrow=20)
  NIR [] <- runif(30*20,min = 1,max = 255)
  RED <- raster(ncol=30,nrow=20)
  RED [] <- runif(30*20,min = 1,max = 255)

  NDVI = ndvi(NIR,RED)
  plot(NDVI)

  ### using example data
  act.ndvi = ndvi(red,nir,cal.reflectance = TRUE, date = "1980-11-14")
  plot(act.ndvi)

DGampe/TriangleMethod documentation built on March 18, 2022, 6:43 a.m.