Why there are differents range in NDVI generate from a MAPIR Survey3 orthophoto and clip?

I have a orthophoto made by RGN filter of a MAPIR SURVEY3 and when i created the NDVI using raster calculator in arcgis the range was from -1 to +1, but when i clip this raster (to use a region of...

24 August 2019 5,224 3 View