How do I compute a Normalized Difference Snow Index (NDSI) in ArcGIS's Raster Calculator? I have a Landsat 8 scene (hdf4 format) that contains derived surface reflectance band-by-band. Each band is a grid 16-bit signed format.
In Raster Calculator, I tried to compute NDSI using the following code:
(float(b3)-float(b6))/(float(b3)+float(b6)), where b3 is Band 3 (Green) and b6 is Band 6 (SWIR). This results in an output of 32-bit and floating point pixel type. However, the resulting NDSI is not scaled from -1 to 1. Instead, the values range from, in this case, -367 to 251. The original surface reflectance for each band ranges from -1000 to 12018.
Does this have to do with rescaling? If I rescale the NDSI output (dividing the output results by 1000), the values still seem low for an ice and snow-covered surface (now, the output values are -0.367 to 0.251).