NDVI values raster computed by using the band 3 and band 4 reflectance values b4-b3/b4+b3. The output raster is of 32bit type formate although the possible ranges that shows in statistics parameter are from -0.35 to +0.65. Are this is due to abnormal values that have been accounted for no data values. If yes then how can i remove those values from the output raster or make them out during the calculation of NDVI in raster calculator.
@Whuber. commented in a post normalize raster, but cannot understand how to do into my case of ration images. there are 5 images that i took for comparison but how do i normalize them to compare easily
Best Answer
You are asking a lot of questions, not just one.
NoData values will be excluded from calculations. If the value of 0 is being used to notate NoData, you are going to have bad results. Check the attribute table to see what your data uses (other popular choices are -999 and the like).
The valid range of NDVI values are {-1, 1}. Your value ranges are within the expected range of NDVI values.
This is not a good idea, but it is possible using a bit of algebra.
Not a good idea because it is already normalized for comparison between images (that's what the N stands for in NDVI). The range of NDVI values are {-1, 1}. Usually < 0 means not vegetation and > 0 means vegetation. It is likely that you need to calibrate your NDVI to your specific images by comparing various pixel thresholds with manually classified data (vegetation/no vegetation) to somewhere around .1-.2.