Indices for optical data

Modified on Thu, 11 Jan 2024 at 10:45 AM

For optical data, the categories and relevant indices are:


Vegetation

  • NDVI: Normalised Difference Vegetation Index. This is the classic index that is the standard default for any vegetation mapping.  
  • EVI: Enhanced Vegetation Index. This includes the blue channel to improve upon the NDVI.  (The values used for the constants are the most commonly used: g=2.5, L=1.0, C1=6.0, C2=7.5.) 
  • SAVI: Soil Adjusted Vegetation Index. This includes a factor to account for background soil contributions (and so is helpful for agricultural studies). (L=1.0).
  • SR: This is a Simple Ratio of NIR/R.


Water

  • NDWI: The Normalised Difference Water Index makes use of reflected near-infrared radiation and visible green light to enhance the presence of water features while reducing the impact of soil and vegetation.
  • MNDWI: Modified Normalised Difference Water Index is more suitable for areas that are dominated by human impact as it is more effective than NDWI at separating water from built-up areas.
  • LSWI: Land Surface Water Index is the normalised difference between the near IR and the short wave IR and is linked to water content in vegetation and soils.
  • WRI: The Water Ratio Index is used for identifying open water bodies or vegetation containing moisture. 


Urban

  • NDBI: The Normalised Difference Built-up Index. It takes advantage of the spectral response of built-up areas and other land cover. 
  • IBI: Index-Based Built-Up Index is a combination of three thematic indices: the soil-adjusted vegetation index (SAVI), the modified normalised difference water index (MNDWI) and the normalised difference built‐up index (NDBI).


Snow

  • NDSI:  The Normalised Difference Snow Index. It picks out high visible reflectance (from the green band) with low short-wave IR (SWIR) reflectance, which is characteristic of snow (rather than clouds, which are high in both).
  • NDSII: Normalised Difference Snow Ice Index. This uses a visible (green) and NIR band to create a normalised difference index that picks out both snow and ice. 
  • S3 Snow Index:  Some studies have shown this to have better accuracy than NDSI. 


Burn

  • NBR:. The Normalised Burn Ratio is a normalised difference between NIR and short-wave IR (SWIR).
  • NBR2: The Normalised Burn Ratio 2 modifies the NBR to highlight water sensitivity in vegetation and may be useful in post-fire recovery studies.
  • CSI: Char Soil Index. A simple index specifically aimed at detecting post-fire effects. 
  • BAI: This is a Burned Area Index that uses NIR and short-wave IR (SWIR).







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