Re: [idvusers] selecting data region across 0 meridian

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

On 3/20/12 7:51 AM, Hein Zelle wrote:
Dear IDV users,

Our meteorologists make intensive use of IDV.  NCEP GFS data is most,
served by a thredds data server via OpenDAP.

When selecting large data fields (e.g. for vertical soundings), it is
desirable to only select a sub-region of data to speed up loading
times.  However, the screen where the data region is selected does not
allow the region to cross the 0-meridian.  This is problematic when
forecasting for north west Europe.

To reproduce:
- select data source (NCEP global grib file)
- select variable (2 m temperature)
- select time steps in "Times" tab
- select spatial region in "Region" tab

The map shown in this region is (correctly) running from 0 to 360,
representing the grib file configuration.  I cannot drag the region
past the 0 meridian.

Is there a way to work around this, other than re-writing the complete
set of grib files to encompass -180:180?  We know how to do this
technically, but it's rather inpractical to re-grid gigabytes of data
every 6 hours just to deal with the 0 meridian ...

It would be great if IDV would allow drawing the region across the 0
meridian, effectively selecting a region from e.g. 340E:360E and from
0:20E, combining them into one.  Any other workarounds are also much
appreciated!


Kind regards,
      Hein Zelle





--
Don Murray
NOAA/ESRL/PSD and CIRES
303-497-3596
http://www.esrl.noaa.gov/psd/people/don.murray/