20021226: Unidata gribdec.tar.Z bundle (cont.)

>From: Unidata Support <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200211192250.gAJMoQ427093 McIDAS gribdec gbtbpds001.bv1

Brian,

I modified Mcmkmcgrid.c to add a new reformat routine ReformatLatLon
that is called for non-ECMWF grid types 2, 3, 4.  This routine stores
grid values that initially look like:

          (90,0)
             +----------+----------+----------+----------+
             |                      #####################|
             |                      #####################|
             |                      #####################|
             |                      #####################|
             |                      #####################|
             |                      #####################|
             |                      #####################|
             |                      #####################|
             +----------+----------+----------+----------+
                                                   (-90,-360)

into a grid that looks like:


          (90,180)              (90,0)
             +----------+----------+----------+----------+
             |#####################                      |
             |#####################                      |
             |#####################                      |
             |#####################                      |
             |#####################                      |
             |#####################                      |
             |#####################                      |
             |#####################                      |
             +----------+----------+----------+----------+
                                                   (-90,-180)
 
This makes McIDAS plotting/contouring routines happy.

The Mcmkmcgrid.c mods will, in fact, work for all grids that span 360
degrees and that have longitudes specified with increasing values to
the west and decreasing values to the east.  Here are examples of what
I mean (all longitudes are in McIDAS convention: West positive):

West Lon         East Lon
----------------+------------------
  180             -180
  190             -170
  270             - 90
  160             -200
    0             -360
  360                0
           etc.

All of the above grids will be decoded so that the Western most longitude
will be 180, and the Eastern most longitude will be -180.  There is _no_
extra overhead in moving the grid points around since Mcmkmcgrid.c
was doing that anyway.

I put together a new gribdec.tar.Z bundle and stuck it in the unix/gribdec
directory of passworded FTP on our ftp server, ftp.unidata.ucar.edu:

machine:   ftp.unidata.ucar.edu
user:      umcidas
pass:      XXXXXX
directory: unix/gribdec
file:      gribdec.tar.Z

This bundle should have all of the modifications that you made to
Mcmkmcgrid.c (as I updated my code from your examples), and it contains
my latest versions of gbtbpds001.bv1 (NCEP) and gbtbpds001.b98v1
(ECMWF). You should, however, your version of Mcmkmcgrid.c and
Mcgribdecoder.c against the code in gribdec.tar.Z check before
overwriting any of your own work.

I have decoded 1 degree AVN grids with the new code and been successful
in plotting resultant 500 mb Z fields over any map/image I displayed.
Even though my tests were not exhaustive, I feel pretty confident
that they correctly do the job that was needed.

Please let me know if you see any problems.

Tom

>From address@hidden Fri Dec 27 15:21:05 2002
>Cc: address@hidden,
>Brice Biggerstaff <address@hidden>
>Subject: RE: 20021226: Unidata gribdec.tar.Z bundle (cont.)

Tom,

Thank you so very, very much!!  Initial tests of the new software seem to
indicate good results.  We are very appreciative of all your hard work!!

Brian