Normalized Vegetation Index

Compute the NDVI from spectral reflectance according to waveband definitions from standards or corresponding to satellite imagers.

Usage

NDVI(spct, imager = "LandsatOLI", wb.trim = FALSE)

Arguments

spct

reflectance_spct or reflectance_mspct object.

imager

character Name of the imager or standard to be used.

wb.trim

logical Flag telling if wavebands crossing spectral data boundaries are trimmed or ignored.

Value

A numeric vector. When the wavelength range of spct does not fully overlap with both wavebands NA is silently returned.

Details

NDVI is used in remote sensing to the diagnose the condition of vegetation, including crops. It is used for Landsat imagery but also at the farm or plot scale using cameras on drones. It is computed as:

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

The waveband ranges used to compute reflectance vary. Even the imagers in the different Landsat satellites 1 to 8 have had somehow different wavelength sensitivities. The NDVI() function uses the waveband constructors Red and NIR defined in this package. Reflectance is averaged over the wavebands using function reflectance.

Note

The value passed as argument to imager must be a valid argument for both Red and NIR. If the desired return value is a data frame, function NDxI can be used to flexibly compute NDVI and any similar index.