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Re: 20051025:ncdump produced unreadable file ("#UNB" instead of number)

Chris Meek <address@hidden> writes:

>  Thanks Ed - I think I have found the problem - there are 
> at least 3 versions of ncdump floating around on the web.
> I was using the 57K + netcdf.dll version ... which produced
> the #UNB. If I use the 185K version with CYGWIN1.DLL
> I get NaN - which is still a problem but at least I know
> what it means. And also with this latter version I get the
> correct # altitudes per event, while before I was (unknown
> to me until I tripped on the #UNB) getting more than the header-
> specified # altitudes - but not reading them all, and even worse 
> maybe some mismatches between various parameter ascii dumps. 
>
>   There is a further version which is 560K and goes with SZLIBDLL.DLL
> ( I can't find the latter for download one the web although it is 
> mentioned in many places).

Hmm. I really don't know what to say about this. Incidentally, are you
also using netCDF from Fortran on this platform? Or you are only using
ncdump and the C library?

>
>   So I still don't know if I am getting the correct data 
>  (and may never know) ... but so far, except for the NaN,
> it seems to fit the header parameters anyway, and it's easy
> to edit out the NaN.  
>
>
>  (This is the problem with black box data and programs .. I much
> prefer straight binary with a text file description) 
>
Well there I can help you. The netCDF format is just a straight binary
format. After the header, which contains all the metadata, the rest of
the data is laid out in the file in a very straightforward way, just
as you would expect.

To calculate the offsets you need, see this:

http://www.unidata.ucar.edu/software/netcdf/docs/netcdf/File-Format-Specification.html

The data in a netCDF file are stored in XDR format. More information
can be found here:

http://www.unidata.ucar.edu/software/netcdf/docs/netcdf.html#Format

Ed

-- 
Ed Hartnett  -- address@hidden