NOAA / NWS's Meteorological Development Laboratory
Degrib (NDFD GRIB2 Decoder)
Subject: Degrib 1.46
Date: Tue, 16 Mar 2004 12:16:42 -0500
From: Arthur Taylor
You all have the unique distinction of being registered on my degrib
(aka NDFD_GRIB2Decoder) mailing list (all 343 of us) (I'd like to
welcome: denim, brownja, tankfrank68, cablaz, sstrum, solson, cfrosk,
crr, letitia.soulliard, pacificwindsurf, andrew.meredith, webmaster,
norik, matthew.jin, ali.rodol, siriphan.clayton, pmvawter,
Scott.Schumann, sjohnson, d_animal, don.tinker, lee)
Please let me know (email me) if you want to unregister. The latest
version of the program is on: www.nws.noaa.gov/mdl/NDFD_GRIB2Decoder/
----------- General News.
1) I believe that Alaska started its operational readiness test on
3/15. Currently the data is not being sent out to the NWS gateway, so
it is not available to us. What this means to us, is that Alaska is
getting closer to being able to give us data, and we should make plans
to handle / use it.
----------- News about this release:
I have just finished putting together version "1.46" (last one that I
announced was "1.44" on 2/17/2004).
This release is mainly focused on being able to handle Alaska grids. In
addition I solved some bugs, and added better handling for surfaces and
some GRIB1 issues.
1) The small polygon shapefiles previously broke if they crossed the
dateline (and you "include missing values"). The Alaska data does not
typically cross the dateline, but the Alaska grid does contain cells
that do. For cells that actually cross the dateline, I needed to create
a 2 part polygon (1 on each side) in order for ESRI to be able to handle it.
2) For big polygon shapefiles that cross the dateline (again you have to
"include missing values"), degrib already had the ability to split the
big polygon at the dateline into two parts. However on the "split off"
polygon, I forgot to make the first point be the same as the last
point. So I didn't close the polygon, which confused ESRI. In addition
when I crossed the dateline, I didn't insert a point on the actual
dateline, which meant that when looked at using a different projection
(polar stereographic) there appeared to be a tiny slice in the grid. I
have now resolved that.
3) Increased the flexibility of "-nameStyle". One can now use various
substitutions to create the name... %e -> element, %V -> valid time, %R
-> reference time, %s -> surface. For more details see
"degrib/docs/degrib.txt". The original -nameStyle 0,1,2,3 should behave
as it has in the past. In addition I added a -nameStyle 4 which is
mapped to "%e_%v_%s.txt", which should come in handy when dealing with
RUC or ETA model data.
4) Updated the GRIB1 handling of units, which should remove the "GRIB1
unit", making it easier to inventory / probe GRIB1 files.
5) Added a "-surface short" and "-surface long" option to the probe
command. This option tells degrib to output what surface the data was
from (useful for RUC and ETA model data). Also introduced "-pntStyle 2"
which is the same as "-pntStyle 1 -surface short".
6a) Found out that ArcGIS (toolbox in particular) really doesn't like
"c:/ndfd/degrib1.4/..." in the path name. It gets confused by the ".",
and can't figure out the file extension. I believe this was while I was
trying to import a grid... Have now switched to "c:/ndfd/degrib14/..."
6b) For ArcGIS users, dealing with projection, you may be interested in
"c:/ndfd/degrib14/arcview"... In there I have: prj.adf (Works best with
a coverage .flt file, import the .flt using the float to grid toolbox
tool, copy prj.adf to the grid directory) and ndfd.prj (Use Arctool box
: Define projection wizard, Select file (.shp file), Select coord system
-> select -> browse for NDFD.prj). I don't have ArcGIS myself, so those
files were created while borrowing someone else's. I'm told they work
fairly well, but if you see ways to improve them, please let me know.
7) Added "-cells true" option, which allows one to use "-pnt" to specify
a grid cell location rather than lat/lon. Example "-pnt 5,5 -cells true"
means find grid cell 5,5, while "-pnt 5,5" means find lat=5, lon=5.
8) Did some fixes to web.tcl (thanks to "chrism") to handle lack of snow
in pr better, and missing directories (for AK). Also added some better
9) For GRIB1 Lat/Lon grids, I now make sure that the longitude is in the
range of 0..360, before "probing" it. This should allow for grids with
a range of 0..-1 => 0...359.
10) Switched to 6 decimal places (from 5) of accuracy for degrees
lat/lon. The GRIB2 specs give 6 decimals, and the only reason for 5 was
to avoid platform specific round off errors.
11) Relabeled the inventory from "#, Byte, ..." to "MsgNum, Byte, ..."
(so it doesn't look like a comment)
12) Added the ability to over-ride not just the radius of the earth, but
to use an ellipsoidal earth (ie override the semi-major and semi-minor
axis). This allows one to experiment with datums, but shouldn't have
much practical value, since the NDFD is on a sphere.
Please let me know if you have problems.