I am currently in a remote sensing course at my university and am working on a change detection project. I am having some trouble creating an ndwi raster from landsat 8 imagery. I am using arcgis 10.5.
I have downloaded the imagery from USGS earth explorer and am running the raster calculator tool to get my output. The formula I am using is:
float(band 3 - band 5)/float(band 3 + band 5)
My output contains low value of -20.4 and high values of 31.3 which definitely seems off to me. I ran a similar calculation on landsat 7 imagery from 2001 and got a result that ranges from -1 to 1. I am very new to the remote sensing field and am stumped on why my results for the landsat 8 imagery are so extreme.
Can anyone provide insight into why this is happening and what I can do to correct my calculations?