I have MODIS-NDVI file. I calculated the anomaly of 13 years (2000-2012) by the following formula:
[{(NDVImax_2000) - (mean_NDVImax)} / (mean_NDVImax)] * 100
in Raster Calculator of ArcGIS.
I am getting the range of NDVI anomaly (of the year 2000) as +55024.3 and lowest value as -47912.7.
I want to ask if this is the right way of doing this because I am not able to interpret the values.
Also, how do I normalize this range of anomaly to highest value as +100% and lowest value as -100% ? (+100% showing the positive deviation from the mean, i.e. gain in vegetation and -100% showing the negative deviation i.e. loss in vegetation.)
Help.
I am using ArcGIS 10.1.
I am also attaching below, the image of the same.
these are some research paper may be useful
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3983931/
http://www.fao.org/giews/earthobservation/asis/index_2.jsp?lang=en
http://www-pord.ucsd.edu/~ltalley/sio219/indeje_etal_jclimate2006.pdf
http://mycoordinates.org/review-of-normalized-difference-vegetation-index-ndvi-as-an-indicator-of-drought/
Dear Anuja Negi,
If I'm right, you want to arrange your data into [-100;100] interval. You can use a linear transformation to change your values using this formula :
100*([2*(Px-Pmin)/(Pmax-Pmin)]-1)
with Px the individual value for each pixel, and Pmin and Pmax the min and max value of the raster NDVI anomaly.
You can do it in ArcGis. This tansformation will only change the range of your data, but not the variability (e.g. histogram will remain the same).
Hope this helps!
Modify a bit your formula and you will get it as follows:
[{(NDVImax_2000) - (mean_NDVImax)} / (mean_NDVImax + NDVImax_2000)] * 100
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