Re: [idvusers] selecting data region across 0 meridian

Hi Hein, Don, all,

Yes, we have two issues open that are related to this capability. The
one Don mentions [CDM-32] lists a number of improvements for the
CDM/netCDF-Java Grid API including cross-seam subsetting.

The other one [TDS-143] looks at the cross-seam problem specifically.
One of the comments lists a number of possible solutions. Basically it
lists some options for what code might be responsible for splitting
requests into two and stitching the resulting data together:

  a) the client application (e.g., the IDV)
  b) helper classes in netCDF-Java
  c) the netCDF-Java Grid API (and other Feature APIs, eventually)
  d) somewhere in the THREDDS Data Server (TDS)

The IDV work required for these options decreases as you go down the
list. But it never goes away. I think the minimum the IDV will need to
do (with options c and d) is:

  1) recognize a dataset as a global dataset (asking netCDF-Java
     in all but the first option); and
  2) present the subsetting in a way that allows the user to make
     a cross-seam requests;

Now, as to the status of this work in the CDM/TDS, it has not been
started and isn't currently slated for the 4.3 release (sorry, the JIRA
issue is a bit out of date). Options c and d definitely won't make it
into 4.3. We might be able to get at least some parts of option b into
release 4.3.

I will talk to Yuan, Julien, and Sean about this and perhaps we can put
it down as an agenda item for some future IDV/McV telecon.

I just added a comment to the TDS-143 JIRA issue with some more detailed
notes on the options listed above. If anyone has comments on those
details, let me know.

Ethan

[CDM-32] https://www.unidata.ucar.edu/jira/browse/CDM-32
[TDS-143] https://www.unidata.ucar.edu/jira/browse/TDS-143

On 3/20/2012 8:17 AM, Don Murray wrote:
> Hi-
> 
> The underlying netCDF-Java library which reads the data does not support
> subsetting across the grid boundary.  Many users have asked for this
> functionality, but it has not yet been implemented.  Perhaps the
> netCDF-Java developers could chime in on when this will be available.
> The Unidata Jira site says it will be slated for version 4.3:
> 
> https://www.unidata.ucar.edu/jira/browse/CDM-32
> 
> but that it is unresolved.
> 
> Don