NOAA / NWS's Meteorological Development Laboratory
Degrib (NDFD GRIB2 Decoder)
Subject: Degrib version 1.17
Date: Tue, 03 Jun 2003 09:55:39 -0400
Organization: DOC/NOAA/NWS - National Weather Service
To: Arthur Taylor
You all have the unique distinction of being registered on my degrib
(aka NDFD_GRIB2Decoder) mailing list (all 61 of us) (I'd like to
welcome: herb.philbrick, jdmn5, parksm, jasonv, and Andy Bailey)
Please let me know (email me) if you want to unregister.
First I'd like to share some news... Evidently Glen Sampson has asked
that some mention of the NDFD GRIB2 Decoder be put into the next article
of the NWS focus. This was due to David Runyan, and Dave Brown's visit
to the Arizona Division of Emergency Management. David Runyan was
evidently impressed by the ease of use, and although Dave Ruth used the
term "plug-n-play", I think from what I read of what David Runyan said,
he would have agreed to that term.
I just wanted to let you all know that I have just finished putting
together version "1.17" (last one that I announced was "1.13" on
The latest version of the program is on:
New to release 1.17:
1) Added the ability to download the data from the http site instead of
just from the anonymous ftp site. The http data feed should be faster
than the anonymous ftp data feed (and they are coming from the same
2) Improved Weather handling in general. This involved adding the ugly
strings to the probe option (instead of an arbitrary number), and
creating what I consider to be a useable weather .dbf file (instead of
just a field of numbers and the prayer that people would look in the
.txt meta file for what those number meant). I am looking for
suggestions to make the .dbf file even more user friendly.
3) Changed orientation of the .shp files so they start in the lower
left. This is the way most grids are defined, but for .flt files,
ArcGIS apparently requires they start in the upper left. I do not feel
that the .shp / .shx / .dbf files should be made difficult for people to
use (and compare to say wgrib output) simply because the .flt file is
not as flexible.
4) Created a method to handle date-line spanning polygon files.
Basically I allow points to be < 180. It is not optimal, but it is
better than having a polygon spanning the globe. Optimally I should
split the polygons on the dateline.
5) Changed the probe option to be nearest point in addition to bi-linear
interpolation. Since I can't tell right now whether data is discrete or
continuous, I have made the default probe option be nearest point.
6) Hopefully fixed all inside out polygons. In 1.13 I had fixed them if
there were no missing values being imbedded into the ArcGIS files, but I
had separate code for when I did want missing values, which had not been
fixed. Since "GRIB1" files tend to not have missing values, they were
more likely to be inside out than the NDFD GRIB2 files.
7) Found a bug in the GRIB1 decoding of the reference value. The effect
was that the field for GRIB1 files they had a constant value subtracted
8) Updated the projection library to the most recent one available from
Albion Taylor at : http://www.arl.noaa.gov/ss/models/cmapf.html.
The dmapf (or version 2 of cmapf) library now allows arbitrary radius
spherical earths, so its no longer restricted to: 6367.47 km. I'd still
recommend that radius since that is what is used in most of the GRIB1
9) Can now probe a "GRIB1" file (in addition to the "GRIB2" file)
10) Made probe pay attention to the -Decimal option (how many decimals
to round to.)
11) Improved usage of "GRIB1" with missing, by using 9999 for missing if
possible. If not, then defaults to what wgrib used which was 9.999e20.
As always, I tested this release on my PC (win 2000), a Linux machine, a
HP-Unix machine, and an AIX-Unix (machine). Although I may have missed
something in my testing, it should at least compile, and run for some of
the test cases. For those of you with access to the NWS NCEP machine,
my current version is in: /nfsuser/g06/we25at/degrib (on snow/frost, I'm
no longer using asp/bsp). For those with access to MDL's GDP or NHDW
machines, see: ~taylor/degrib/
Please let me know if you have problems.