Re: 20050922:DODS/THREDDS confusion

• To: David Wojtowicz <davidw@xxxxxxxx>, dods-tech@xxxxxxxxxxxxxxxx
• Subject: Re: 20050922:DODS/THREDDS confusion
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Thu, 22 Sep 2005 15:26:01 -0600

Hi David:

The problem is that the opendap server ("DAP++ 3.5.2") uses this form for 
Strings:

forecasttime:   Array of Strings [record = 0..4][time_len = 0..20]
   * long_name: "forecast date and time"

using the "translate a char into a String" method.

However, the THREDDS server uses variable length Strings:

forecasttime:   Array of Strings [record = 0..4]
   * long_name: "forecast date and time"
   * DODS:
         o strlen: 21
         o dimName: time_len

using the "strlen Convention" to tell the client what the String lengths are.


Does anyone on dods-tech know if the opendap-netcdf client library will support 
the latter?

Unidata Support wrote:

------- Forwarded Message

To: support@xxxxxxxxxxxxxxxx
From: David Wojtowicz <davidw@xxxxxxxx>
Subject: DODS/THREDDS confusion
Organization: UCAR/Unidata
Keywords: 200509221824.j8MIOEYJ003573

Hi,

I'm primarily using the Dataset Viewer to browse the catalog and locate DODS URL's that I access in my own applications via the latest OpenDAP libraries.

2) If I locate an entry inside "Previous version OPeNDAP NetCDF Server" I can get a DODS URL like this:

http://motherlode.ucar.edu/cgi-bin/dods/DODS-3.4.3/nph-dods/dods/ model/2005092215_ruc_211.nc

I can do a "dncdump -h" on that URL and get the expected header info.... and also use this URL within my own programs to access the dataset.

However, I'm reluctant to continue using that as the name "Previous version" implies that it's being replaced by something newer and is going to go away.

The "new" entries such as under "NCEP Model Data (netCDF) " I get different OpeNDAP URLs that look like:

http://motherlode.ucar.edu:8080/thredds/dodsC/model_nc/ ruc_211/2005092213_ruc_211.nc

If I pass this URL to "dncdump -h" I get output that is both incomplete and contains invalid data. Tried this with a number of other data files in the same area.

The "NCDUMP" function in the Dataset Viewer program however, seems to work fine.

Is this a different format/protocol? I'm using the latest available SDKs... "DAP++ 3.5.2" and "netCDF Client Library 3.5.2" that I downloaded from opendap.org and compiled myself under linux.

I'm further frustrated by the fact that most of the documentation/ status pages that I find on www.unidata.ucar.edu haven't been updated in a while and don't reflect recent changes.

David Wojtowicz, Sr. Research Programmer
Dept of Atmospheric Sciences / Computer Services
University of Illinois at Urbana-Champaign
davidw@xxxxxxxx  (217) 333-8390



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