| NDVI {photobiologyWavebands} | R Documentation |
Normalized Vegetation Index
Description
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. |
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.
Value
A numeric vector. When the wavelength range of spct does not
fully overlap with both wavebands NA is silently returned.
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.