Re: [idvusers] HOW TO : Plot views across the prime meridian using IDV

Hi Ian-

Thanks for sharing this with the group.  This will be good for those
who want to subset the gridded datasets.

Now that I'm back from holiday, I've had a chance to work on the IDV side of this issue of the gap when the last grid point does not overlap
the first.  I just put out a new nightly build (2.5a1) that extends
the grid if need be so there is no longer a gap at the edge.  If
anyone wants to test that for me, I'd welcome feedback.  You can
download the latest nightly build from:

http://www.unidata.ucar.edu/downloads/idv

I've tested with the Global 2.5, 1.0 and .5 degree grids on our
UCAR server.

Don Murray

webmaster-IWC wrote:
Hi all,
OK I have managed to get around this problem with plotting across the
prime meridian - and it works, which did surprise me!
So I thought I would share how this can be done.
Data set
GFS global model 1x1 deg from NCEP
Software required
IDV (unidata | display)
Cnvgrib (NCO | convert grib 2 to grib 1)
Convsh + Subset.tcl (BADC | create regional subsets into NetCDF)
1. First download your data. You need to download the whole grid as
cnvgrib will not work with partial downloading of grib files
2. Use Cnvgrib to convert grib 2 files into grib 1 (Example cnvgrib -g21
gfs.t00z.pgrbf09.grib2 subset.grb)
3. Create a regional subset from the new grib 1 file data set (Example
convsh subset.tcl -i subset.grb -o subset.nc -xs -60 -xe 60 -xi 1 -ys 0
-ye 90 -yi 1)
The new subset file is now in NetCDF format with the starting grid lon @
-60, this fixes the problem that IDV has plotting across the meridian.
FOR XP USERS ONLY. I have complied copy of Cnvgrib.exe if any users require this. Other programs and documents needed can be found below: BADC
HYPERLINK
"http://badc.nerc.ac.uk/help/software/xconv/#utilites"http://badc.nerc.a
c.uk/help/software/xconv/#utilites
HYPERLINK
"http://badc.nerc.ac.uk/help/software/xconv/subset.html"http://badc.nerc
.ac.uk/help/software/xconv/subset.html
NCO
HYPERLINK
"http://www.nco.ncep.noaa.gov/pmb/codes/GRIB2/"http://www.nco.ncep.noaa.
gov/pmb/codes/GRIB2/
Good luck and have fun Ian
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*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************