Normalized Difference Bare ice Index, NDBI

//VERSION=3

// Normalized Difference Bare ice Index, NDBI
// Source: https://www.mdpi.com/2072-4292/11/19/2280
// Values between 0 and 0.2 correspond to snow
// Values between 0.2 and 0.5 correspond to bare ice
// Values between 0.5 and 0.8 correspond to dark (melting) ice
// Thresholds may be adapted depending on local conditions.

function setup() {
  return {
    input: ["B02", "B21"],
    output: { bands: 3 }
  };
}

function evaluatePixel(sample) {

  // Calculate NDBI
  var NDBI = index(sample.B02, sample.B21);

  // Color depending on class
  if ((NDBI > 0) & (NDBI < 0.2)){
    return [179/255, 203/255, 255/255]; // Snow
  } else if ((NDBI >= 0.2) & (NDBI < 0.5)){
    return [255/255,204/255,204/255]; // Ice
  } else if ((NDBI >= 0.5)&(NDBI < 0.8)){
    return [0/255,0/255,255/255]; // Dark ice
  } else {
      return [0,0,0]; // Shadows, water...
  }
}

Evaluate and Visualize

• Copernicus Browser
• EO Browser

General description of the script

The Sentinel-3 OLCI Normalized Difference Bare ice Index (NDBI) was developed by Kokhanovsky et al. (2020) to differentiate snow-covered surfaces from bare ice. NDBI used two bands: one in the Blue (Band 2, 412.5 nm) and one in the NIR (Band 21, 1020 nm).

Formula: (Band 02 - Band 21) / (Band 02 + Band 21)

The surface types corresponding to NDBI values are shown in the table below. The thresholds may be modified depending on local conditions.

Values	Surface
0–0.2	Snow
0.2–0.5	Bare ice
0.5–0.8	Dark ice (melting)

Description of representative images

1. NDBI of South Greenland, acquired on 29 August 2019.
   
2. Classified NDBI map of South Greenland, acquired on 29 August 2019 (Light blue = snow, pink = ice, dark blue = dark ice, black = other surfaces).
   
3. For comparison purposes: RGB (B17, B07, B03) image of South Greenland, acquired on 29 August 2019.)
   

Contributors:

Maxim Lamare