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Re: Question about TDS OpenDAP

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  • Subject: Re: Question about TDS OpenDAP
  • Date: Tue, 17 Jan 2012 09:38:05 -0700
Hi Estani:
1. a dods file is not a netcdf file, although i think there are some versions of ncdump that can work with dods. in short, you cant "get the netcdf file" through opendap.
2. it appears that the original file is netcdf, so you may just want to download the original file, in TDS you do that by enabling the "fileserver" service. note that you are just downloading the file to your local drive.
3. the metadata in the das and dds returns are equivalent to ncdump -h, if thats all you want.
4. panolpy uses the netcdf-java library, so it should work with the opendap endpoint.
5. recent versions of the netcdf C library can also work directly with the file remotely, through opendap. 

john

On 1/17/2012 8:50 AM, Estanislao Gonzalez wrote:

Hi,

This is what a user tried to do and it didn't work:
ncdump
http://bmbf-ipcc-ar5.dkrz.de/thredds/dodsC/cmip5/output1/MPI-M/MPI-ESM-LR/rcp45/6hr/atmos/6hrPlev/r1i1p1/v20111006/psl/psl_6hrPlev_MPI-ESM-LR_rcp45_r1i1p1_2006010100-2006123118.nc 
2> nc_dump_log.txt
The security is not the issue here as I can get it through the normal browser. AFAIK these are the supported OpenDAP formats: 
.ascii - txt
.dods - some binary format (not NetCDF)
.dds - doesn't work with Gateway but it's just the metadata anyway
.das - doesn't work either for the same reason and I have no idea what it is (attribute values?)
I've downloaded the dods file, as I was going to tell the user this is what he should be downloading, but I couldn't open it with NASAs Panoply. I guess that's because it's not a NetCDF stream, it's some OpenDAP half binary stream. I don't have the ncdump program so I can't test this (the one I could find was linked to the 4.1.1 library and AFAICT it won't work because of the security.
Basically, the question would be: is it possible to get the NetCDF file via OpenDAP? Should the user directly access the fileServer endpoint for that, even using ncdump? 
Should *.nc.dods be the default endpoint for those cases?

Any information on  the subject would be greatly appreciated :-)

Thanks,
Estani