This tutorial demonstrates how to calculate NDBI using ERDAS Imagine Model Maker or Spatial Modeller.
The Normalized Difference Built upIndex (NDBI) is an index of built up or urban areas where there is typically a higher reflectance in the shortwave-infrared (SWIR) region, compared to the near-infrared (NIR) region.
NDBI = (SWIR – NIR) / (SWIR + NIR )
NDBI values range from +1.0 to -1.0. NDBI is useful in applications include land-use planning and hydro-logical modeling .