Without knowing the exact products you're using, I can't say for sure. But
most likely the scaling factor is 10,000.  So if you divide the raster
values by 10,000 you will get the raw values you're looking for.

You should definitely read the metadata for any MODIS product carefully so
you know what the raw, digital numbers are.  But 10,000 is a pretty
standard scaling factor for shifting floating point numbers to integers,
and is used for a wide variety of remotely sensed data in order to decrease
the file size requirement for storing certain data.

Good luck,
Forrest Stevens
-- 
Ph.D. Candidate, QSE3 IGERT Fellow
Department of Geography
Land Use and Environmental Change Institute
University of Florida
www.clas.ufl.edu/users/forrest

On Fri, Sep 21, 2012 at 5:50 PM, dlarsen <dlarsen@tulane.edu> wrote:

> Hi all,
>
> I am trying to generate temperature and EVI for points in my dataset, but
> the values I am extracting are strange.  The EVI values range from 627 -
> 9149 with a mean of 4912.861.  The EVI values range from 14933 to 15800
> with
> a mean of 15549.66.  Is there some type of conversion that I am missing?
> Here are the steps I took.  (I know many of them are inefficient, but I am
> doing this for my dissertation without a lot of support).
>
> 1.  Download HDF files using Earth Explorer
> 2.  Use MODIS Reprojection tool to convert to vegetation indices and
> temperature tif files.
> 3.  Use the raster package in R to extract the values of the tif file to
> spatial points.
>
> Any help would be appreciated.
>
> Thank you,
> David
>
>
>
> --
> View this message in context:
> http://r-sig-geo.2731867.n2.nabble.com/Extracting-weird-temperature-and-EVI-values-from-MODIS-data-tp7581006.html
> Sent from the R-sig-geo mailing list archive at Nabble.com.
>
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