How to calculate NDVI using Erdas Imagen
A vegetation index is a transformation that can be used to map the “greenness” of vegetation.
The Normalized Difference Vegetation Index (NDVI) is a normalized ratio of two bands, NIR and red (typically, TM bands 4 and 3), where NIR and Red are the DN values in the near IR and red spectral bands.
The formula for NDVI is:
NDVI= (NIR-Red) / (NIR + Red)
Looking at your NDVI image result, note the NDVI values for different areas of the image:
- Pixels with values less than 0 are usually water
- Pixels with low values close to 0 are bare areas (soils, pavement, etc.)
- Pixels with higher values are vegetation
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