Re: long variable name problem inside IDV

Hi Kent, Joe:

Theres no 15-char limit anywhere, the problem is that the opendap/hdf server is 
coding a signed byte as a unsigned byte. its actually a limitation of the DAP, 
which doesnt have signed bytes. 

for more info: <http://scm.opendap.org/trac/ticket/1199>

We have a workaround for now that allows the dataset to be read anyway, 
although there may be trouble correctly interpreting the byte variable(s).  the 
next 4.0 release will have the fix, youll have to check with the IDV folks as 
to their release schedule.

I've recommended that they add signed bytes to the DAP. if they do, the hdf 
server would have to be updated to take advantage of that.

H. Joe Lee wrote:
> Hi, John!
> 
> If I relax the 15 character limit in DAS(attributes) output from
> OPeNDAP, I get an error like below:
> 
> ucar.unidata.data.BadDataException: Error creating data
> source:dods.grid with:
> http://hdfdap.hdfgroup.uiuc.edu:8888/opendap/data/OMI-Aura_L3-OMDOAO3e_2008m0101_v003-2008m0222t135958.he5
> Unable to open grid:
> dods://hdfdap.hdfgroup.uiuc.edu:8888/opendap/data/OMI-Aura_L3-OMDOAO3e_2008m0101_v003-2008m0222t135958.he5
> 
>       at ucar.unidata.data.DataManager.createDataSource(DataManager.java:1379)
>       at 
> ucar.unidata.idv.IntegratedDataViewer.createDataSource(IntegratedDataViewer.java:1847)
>       at 
> ucar.unidata.idv.IntegratedDataViewer.makeDataSource(IntegratedDataViewer.java:1766)
>       at 
> ucar.unidata.idv.IntegratedDataViewer.makeDataSource(IntegratedDataViewer.java:1700)
>       at 
> ucar.unidata.idv.IntegratedDataViewer.handleAction(IntegratedDataViewer.java:1554)
>       at ucar.unidata.idv.DefaultIdv.handleAction(DefaultIdv.java:112)
>       at 
> ucar.unidata.idv.IntegratedDataViewer.handleAction(IntegratedDataViewer.java:1486)
>       at ucar.unidata.idv.chooser.UrlChooser.loadURLInner(UrlChooser.java:249)
>       at ucar.unidata.idv.chooser.UrlChooser.loadURL(UrlChooser.java:221)
>       at 
> ucar.unidata.idv.chooser.UrlChooser.doLoadInThread(UrlChooser.java:268)
>       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>       at 
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
>       at 
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>       at java.lang.reflect.Method.invoke(Method.java:585)
>       at ucar.unidata.util.Misc$2.run(Misc.java:990)
>       at ucar.unidata.util.Misc$3.run(Misc.java:1018)
> 
> 
> What could be wrong?
> 
> On Fri, Sep 26, 2008 at 1:22 PM, John Caron <address@hidden> wrote:
>> Hi Kent:
>>
>> I think Joe is mistaken, there is no 15 char limit either in CF or in the 
>> IDV/netcdf-java stack. Im guessing that he has unnecessarily truncated to 15 
>> chars in the server.
>>
>> He is right that a file must follow a coordinate convention like CF. Opendap 
>> grids alone do not have sufficient semantics to allow geolocation.
>>
>> If you can send me a sample HDF5-EOS file i can comment further.
>>
>> MuQun Yang wrote:
>>> Hi John,
>>>
>>> We found a limitation inside IDV that doesn't allow the variable name to
>>> be longer than 15 characters. This is a problem for EOS data whose
>>> variable name may be longer than 15 characters. We sent an email to one
>>> of IDV developer but have never received a reply(See the email below).
>>> Could you help us build up the connection? IDV is a cool tool. If it can
>>> support long variable name, that will be perfect.
>>>
>>> Thanks,
>>>
>>> Kent
>>>
>>> The name of the first contact is Jeff McWhirter.
>>> We got his name from this list:
>>>
>>> http://www.unidata.ucar.edu/about/staff.jsp
>>>
>>> ---------- Forwarded message ----------
>>> From: H. Joe Lee <address@hidden>
>>> Date: Wed, Aug 27, 2008 at 11:25 AM
>>> Subject: [Q] IDV and OPeNDAP Grid variable name length?
>>> To: address@hidden
>>>
>>>
>>> Hi, Jeff!
>>>
>>> My name is Joe and I'm working on OPeNDAP HDF5 handler project at The
>>> HDF Group. I got your e-mail from Unidata's staff list web page.
>>>
>>> In the OPeNDAP HDF5 handler, I've implemented a configuration option
>>> to support IDV client for NASA HDF-EOS5 HDF5 files. During the handler
>>> testing, I noticed that IDV couldn't handle OPeNDAP Grids that have
>>> variables whose names are longer than 15 characters. Is my observation
>>> true? If so, do you know why such restriction is enforced in IDV or
>>> know how to relax such restriction?
>>>
>>> You may also be interested in reading my technical note with the
>>> OPeNDAP HDF5 handler:
>>>
>>>   http://hdfdap.hdfgroup.uiuc.edu:8080/cf.html
>>>
>>> Regards,
>>>
>>> --
>>> -- Joe
>>>
>>>
>>>
>>
> 
> 
>