The NDVI (Normalized Difference Vegetation Index) is a widely used indicator for assessing the presence, density, and health of vegetation in a specific area. It is based on the difference in reflectance between the red and near-infrared (NIR) spectral bands, which are sensitive to chlorophyll and plant structure.
NDVI values range from -1 to +1. Higher values generally correspond to dense and healthy vegetation, while lower or negative values indicate bare soil, urban areas, or water bodies. These interpretations are often used in agricultural monitoring, environmental management, and land use classification.
NDVI Classification.
Bands Used for NDVI Calculation
The bands used for NDVI vary depending on the satellite sensor. The following are the typical band assignments:
- Landsat 8/9: Band 4 (Red), Band 5 (NIR)
- Sentinel-2: Band 4 (Red), Band 8 (NIR)
It is essential to identify the correct bands before applying the NDVI formula, especially when working with multispectral imagery from different satellite platforms.
Using the Raster Calculator
To manually calculate the NDVI in ArcGIS Pro, the “Raster Calculator” tool is used. It is located in:
Geoprocessing > Toolboxes > Spatial Analyst Tools / Image Analyst Tools > Map Algebra > Raster Calculator
In the calculator, the NDVI formula is entered as follows:
NDVI = (NIR – Red) / (NIR + Red)
Replace “NIR” and “Red” with the actual band names or layer references being used in the project. For example, if using Landsat 9, input the file names corresponding to Band 5 and Band 4 respectively.
The output will be a new raster layer that displays a gradient of values representing vegetation cover. Typically, the visualization uses a color ramp where areas with low or no vegetation appear in red tones, while areas with healthy vegetation appear in green.
Calculation of NDVI with “Raster Calculator”.
It is important to interpret the NDVI values carefully, as different vegetation types and environmental conditions can affect the index. The resulting NDVI map can be further analyzed or exported for reporting and decision-making purposes.