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 my interest) the ndvi values go from +0,19 to +0,42. I think that these values don't represent the reality. How can i make to let these values from -1 to +1? Is any resampling problem?
Thank you.
Usually, negative NDVI values represent water bodies. Positive values closer to 0 represent bare lands, built up areas, etc. Mid positive values (e.g. ~ 0.3-0.6) represent spare to moderate vegetation cover. High NDVI values (e.g. ~ >0.6) represent dense vegetation. Once you've clipped your layer, most probably the areas consists of water bodies (e.g. sea) might have become excluded from your raster, which explains absence of negative NDVI values. If you stretch the values again from -1 to +1, the values will become meaningless.
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