SR

Synthèse

Calculates the Simple Ratio (SR) from a multiband raster object and returns a raster object with the index values.

Discussion

La méthode SR (Simple Ratio, Ratio simple) est un indice de végétation courant qui permet d’estimer l’étendue de la végétation. Il s’agit du ratio de luminosité dispersée dans le canal NIR et absorbé dans le canal rouge, qui réduit les effets de l’atmosphère et de la topographie.

Values are high for vegetation with a large leaf area index, or high canopy closure, and low for soil, water, and nonvegetated features. The range of values is from 0 to approximately 30, where healthy vegetation generally falls between values of 2 and 8.

SR = NIR / Red

For information about other multiband raster indexes, see the Band Arithmetic raster function.

The referenced raster dataset for the raster object is temporary. To make it permanent, you can call the raster object's save method.

Syntaxe

SR (raster, {nir_band_id}, {red_band_id})

Paramètre	Explication	Type de données
raster	The input raster.	Raster
nir_band_id	The band ID of the near-infrared band. The ID index uses one-based indexing. (La valeur par défaut est 5)	Integer
red_band_id	The band ID of the red band. The ID index uses one-based indexing. (La valeur par défaut est 4)	Integer

Valeur renvoyée

Type de données	Explication
Raster	The output raster with SR values.

Exemple de code

SR example

Calculates the Simple Ratio for a multispectral image.

import arcpy

SR_raster = arcpy.ia.SR("MSimage.tif",5,4)