-1

It is in the literature that areas covered by snow would have a Normalized-Difference Snow Index (NDSI) >0.4. I also found other literature with different thresholds like >0.7 in the high Arctic, and others showing differences between seasons.

In NDSI from Landsat available in Google Earth Engine, values go from 0 to 1, so what do the other values mean?

  • Really, can you provide an example of that? The word normalized rather implies that the range goes from 0-1. – John Powell Sep 1 '17 at 16:48
1

Are you sure than GEE index goes from -1.2 to 1.2? It's a normalized difference, can be out of this range (if TOA or BOA values are negative, could be, but those aren't valid values).

Check this example:

var imageCollection = ee.ImageCollection("LANDSAT/LC08/C01/T1_RT_TOA");

var ndsi = function(image){
  return image.normalizedDifference(['B3', 'B6']);
};

var snow_index = imageCollection.map(ndsi);

Map.setCenter(-44.2,62.39,10)
Map.addLayer(snow_index);

Values never are over 1 (in Greenland!):

enter image description here

Over 0.4 seems to be an optimum range, I recommend you to find a weather station near to your study area and compare snow pillow with NDSI.

  • I guess you are right! the values are -0.2 to 1, it was something from the histogram, but the values lower than 0 and higher than 1 are empty, thanks! – MSS Sep 1 '17 at 16:59

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