Tom Whittaker wrote:
I found there has been some discussion about having a variable
attribute "_Unsigned" that would allow for unsigned byte data to be
supported. Well, one of our people created a netCDF file with bytes
which he treated as "unsigned"....but when he read the file and
specified a (float) scale and offset, he got the "wrong"
answers...until he started treating the byte values as signed -- his
unhappiness is that IDL apparently treats bytes as unsigned, so he
cannot easily use his file in both (IDV is the other one) places. I
tried a few combinations in the toosUI, using NCML, but could not get
anything to work...
Is this supported? If so, is there some magic? (I'm running netCDF-java 4.1).
Thanks...
tom
Hi Tom:
Classic netcdf has only signed bytes. netcdf-java introduced the concept
of unsigned bytes by adding an attribute
varname:_Unsigned = "true";
This only matters to the library when you are doing scale/offset. of
course, the application also wants to deal with it when using it in
calculations, see:
http://www.unidata.ucar.edu/software/netcdf-java/reference/DataType.html
for more info.
If IDL insists on treating bytes as unsigned, then storing as unsigned
with attribute as above should work in both places. If you have a file
where this isnt working in IDV, send it to me and ill check it out.
