I am trying to calculate index based built-up index (IBI) in ArcMap using raster calculator and getting strange values. I downloaded Landsat 8 data and using green, red, NIR and SWIR1 bands for the equation:
IBI = (NDBI - (SAVI + MNDWI) / 2) / (NDBI + (SAVI + MNDWI) / 2)
I followed the equations in this article to get all the indexes needed for IBI https://link.springer.com/article/10.1007%2Fs10708-020-10148-w
My result values for IBI range from -3.10538e+07 to 2.53846e+07, which is rather strange. My NDBI values range from -0.64 to 0.66, SAVI from -0.33 to 1.47, MNDWI from -0.98 to 0.47. All these 3 rasters seem to correct. I can't really get my head around where the mistake is.
Any suggestion? I would be really grateful for any help.
Well I tried setting your variables to their lowest values:
ndbi = -0.64
savi = -0.33
mndwi = -0.98
Then pumped them into your equation and it generate:
ibi = (ndbi - (savi + mndwi)/2)/(ndbi+(savi+mndwi)/2)
ibi = -0.011583011583011595
Which is nothing like your erroneous values, so unless you show us how you ran the tools no one is going to be able to help you.