What considerations should be taken into account when trying to derive a NDVI from an urban environment?
I pulled a tree canopy layer from LAR-IAC data and used an NDVI of 0.38. However, this FAQ on Vegetation in Remote Sensing recommends using >0.8, while I've read >0.6 as a good NDVI for dense vegetation. Is 0.38 too low, and is it possibly lower because of an urban environment (Pasadena, CA)? Should I be using an alternative index, like SAVI (Soil Adjusted Vegetation Index), but maybe for urban areas?