[netcdf-java] Creating geoTiff - retaining data values

[Jeff Van Dorn]

Hello all,

I'm attempting to create geoTiff images from a large number of netCDF  
files.

A portion of my test code is below:

LatLonPointImpl p1 = new LatLonPointImpl(38.0625, -80.6875); // lower  
left
LatLonPointImpl p2 = new LatLonPointImpl(47.8125, -67.0625); // upper  
right
LatLonRect llr = new LatLonRect(p1, p2);
GeotiffWriter writer = new GeotiffWriter 
("NE_1961-1990_Yearly_Max_Temp.tif");
writer.writeGrid("NE_1961-1990_Yearly_Max-Temp.nc", "tmax", 0, 0,  
true, llr);

(netCDF file here: http://temagami.tosm.ttu.edu/~jvandorn/netcdf/ 
NE_1961-1990_Yearly_Max_Temp.nc)

This does produce a viewable image from the netCDF file:
(viewable here: http://temagami.tosm.ttu.edu/~jvandorn/netcdf/ 
netcdfLibToTiffGrayScaleTrue.tif)

However the pixel values in the tif image when viewed in something  
that works with geoTiffs (e.g., Mirone) do not reflect their original  
values.  Meaning, the original input netCDF file is showing maximum  
temperatures (http://temagami.tosm.ttu.edu/~jvandorn/netcdf/ 
NE_1961-1990_Yearly_Max_Temp.png), which roughly range from 7 to 25  
oC (with a missing value of -999), but the resulting tiff scale seems  
to range from 1 to 255.

Per the API, there's a boolean greyScale setting in the  
GeotiffWriter.writeGrid method.  Is this the expected result when  
that is set to true?  That it outputs a grey scale image, where the  
pixel values are now in terms of 1 to 255, instead of their original  
values?

I've tried setting grayScale to false, in hopes that it would  
actually retain the original data values but nothing really seems to  
make much sense of that result:
(http://temagami.tosm.ttu.edu/~jvandorn/netcdf/ 
netcdfLibToTiffGrayScaleFalse.tif).

So, my basic question is, can I produce a geoTiff image that will  
contain the same range of pixel (i.e., data) values that the original  
netCDF file shows?

Thank you for any help/suggestions on this.
Jeff
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