[idvusers] selecting data region across 0 meridian

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

Kind regards,
     Hein Zelle


Dr. Hein Zelle
Advisor Meteorology & Oceanography

Tel:        +31 (0)527-242299
Fax:        +31 (0)527-242016
E-mail:     hein.zelle@xxxxxxxxxxxxx
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