NDSI

Summary

Calculates the Normalized Difference Snow Index (NDSI) from a multiband raster object and returns a raster object with the index values.

Discussion

The Normalized Difference Snow Index (NDSI) is designed to use MODIS (band 4 and band 6) and Landsat TM (band 2 and band 5) for identification of snow cover while ignoring cloud cover. Since it is ratio based, it also mitigates atmospheric effects.

 NDSI = (Green - SWIR) / (Green + SWIR)

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.

Syntax

NDSI (raster, {green_band_id}, {swir_band_id})

Parameter	Explanation	Data Type
raster	The input raster.	Raster
green_band_id	The band ID of the green band. The ID index uses one-based indexing. (The default value is 4)	Integer
swir_band_id	The band ID of the shortwave infrared band. The ID index uses one-based indexing. (The default value is 6)	Integer

Return Value

Data Type	Explanation
Raster	The output raster object with the NDSI values.

Code sample

NDSI example

Calculates the Normalized Difference Snow Index for a Landsat 8 image.

import arcpy

NDSI_raster = arcpy.ia.NDSI("Landsat8.tif", green_band_id = 4, swir_band_id = 6)

NDSI example

Calculates the Normalized Difference Snow Index for a Landsat 8 image.

# Import system modules
import arcpy
from arcpy.ia import *

# Set the analysis environments
arcpy.env.workspace = "C:/arcpyExamples/data"

# Set the local variables
in_raster = "landsat8.tif"

# Execute NDSI function
out_ndsi_raster = NDSI(in_raster, 4, 6)

# Save the output
out_ndsi_raster.save("C:/arcpyExamples/outputs/NDSI.tif")