20021205: Unidata gribdec.tar.Z bundle (cont.)

>From: "HOETH, BRIAN R. (JSC-ZS) (LM)" <address@hidden>
>Organization: JSFC
>Keywords: 200211192250.gAJMoQ427093 McIDAS gribdec gbtbpds001.bv1

Brian,

>Thanks again!

No worries.

>Couple more things:
>
>(1) I made a minor mod to Mcgribdecoder.c in the grib_dec_is function.  I
>had to compare t_value to GB_MAX_BDS_LEN instead of GB_MAX_MSG_LEN or else
>some of the 12km ETA GRIB records would not decode?  I've attached my
>version if you're interested?

Your version was not attached.  I took a look at Mcgribdecoder.c and
see that GB_MAX_MSG_LEN is defined to be smaller than GB_MAX_BDS_LEN
which does not appear to make sense as GB_MAX_MSG_LEN is supposed to be
"maximum length of the full GRIB message".  Without having really
thought about the ramifications, the fix would seem to be to alter
GB_MAX_MSG_LEN in grib.h to be as large or larger than any of the
portions of the grib message and then rebuild the decoder.

>(2) I am noticing that using GRDDISP with the GFS

GFS ??? what is this?

>has lots of bugs for
>regions that are not over the US?  I believe it has something to do with
>something you had mentioned about not plotting over the International Date
>Line because when I do a MAP WORL and then plot the 500mb wind barbs, all
>the barbs line up on the International Date Line?

I can't comment without knowing what GFS is.  Your comment sounds like
what I was driving at.  If you let GRDDISP plot the map for the full
grid, then displays look correct.  If you try to overlay on top of a
display that you choose, things don't work correctly.  The question of
what is wrong boils down to the McIDAS notion of the Longitude extent
possibilities for grids.  The last thing I sent you was a suggestion to
set the UL and LR Lat,Lon points for grids 2, 3, and 4 so that the
lower right point is at -360.  This may fly in the face of preconceived
notions in McIDAS for possible grid Lat,Lon extents.  I will have to
touch base with Dave Santek on this one.  The one thing that I really
don't want to do is have to reformat the grid so that its Lat,Lon
extents lie between 90,180 and -90,-180.  This would be a lot of work
for the grib decoder especially if it is to be used in XCD.  This may,
however, be the "real" solution to the problems we are seeing with
gribdec.k.

>If I try plotting the
>500mb wind barbs over a satellite image over Europe, I get the following
>error:
>
>Invalid Maximum Longitude
>2nd Longitude= argument is too small --> -359:0:0
>Must be valid 'Maximum Longitude' lat/lon within range +/- 1800000
>Failed to draw map .... ending program

Same problem as I allude to above.

>Any ideas on how to reconcile this?

See above.

>Like I said before, perhaps an inquiry
>to SSEC would be in order?

A contact with Dave Santek is most likely the first place to start.
I will try calling him soon.

>I think I saw that McIDAS 2002 addressed
>something about the International Date Line?

Different problem.

Tom