NDVI, NDBI, NDSI, SAVI- Erdas Imagine
Table of Contents
NDVI
The NDVI stand for Normalized Difference Vegetation Index, its describes the vegetation density and assessing changes in plant health. NDVI is calculated as a ratio between the red (R) and near-infrared (NIR). In this tutorial, learn how to apply the NDVI Formula and calculate vegetation patterns.
Process of NDVI
NDVI Formula
(NIR – R) / (NIR + R)
In Landsat 4-7, NDVI = (Band 4 – Band 3) / (Band 4 + Band 3).
The Landsat 8, NDVI = (Band 5 – Band 4) / (Band 5 + Band 4).
IRS Liss-III, NDVI = (Band 3 – Band 2) / (Band 3 + Band 2).
NDVI always ranges from -1 to +1.
How to apply NDVI Formula
1.On the Raster tab, the Classification group expend Unsupervised, and selects NDVI.
2. The Indices dialog is open, select Input file and Output file, and most important, choose Sensor (ex. IRS LISS-III) for your Satellite image.
3. Band selection box is automatically selected. Now click OK.
NDBI
Normalized Difference Built-up Index (NDBI) describes the Built-up density of any Geographic area. NDBI is calculated as a ratio between the shortwave infrared (SWIR) and near-infrared (NIR).
Process of NDBI
NDBI Formula
(SWIR – NIR)/(SWIR + NIR)
NDBI ranges from -1 to +1.
How to apply NDBI Formula
1.On the Raster tab, the Classification group expend Unsupervised and select Indices.
2. The Indices dialog is open, select Input file and Output file, and most important choose Sensor (ex. IRS LISS-III) for your Satellite image. Now select NDBI in the Index box.
3. Band selection box is automatically selected. Now click OK.
NDSI
Normalized Difference Snow Index (NDSI) describes the Snow cover for any area. NDSI is calculated as a ratio between the visible (VIS) and mid-infrared (MIR).
Process of NDSI
NDSI Formula
(VIS– MIR)/(VIS+ MIR)
NDSI ranges from -1 to +1.
How to apply NDSI Formula
1. On the Raster tab, the Classification group expend Unsupervised and select Indices.
2. The Indices dialog is open, select Input file and Output file, and most important, choose Sensor (ex. IRS LISS-III) for your Satellite image. Choose NDSI in the Index box.
3. Band selection box is automatically selected. Now click OK.
SAVI
Soil Adjusted Vegetation Index (SAVI) is similar to NDVI, these enhancements are useful, because SAVI accounts for variations in soils. SAVI is calculated as a ratio between the near-infrared (NIR), red (RED), and L (Vegetation cover current factor).
Process of SAVI
SAVI Formula
(NIR– RED)*(1+L) / (NIR+ RED+L)
SDVI ranges from -1 to +1.
How to apply SAVI Formula
1.On the Raster tab, the Classification group expend Unsupervised and select Indices.
2. The Indices dialog is open, select Input file and Output file, and most important, choose Sensor (ex. IRS LISS-III) for your Satellite image. Choose SAVI in the Index box.
3. Band selection box is automatically selected. Now.
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