NOAA / NWS's Meteorological Development Laboratory
Degrib (NDFD GRIB2 Decoder) 
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NOAA / NWS's Meteorological Development Laboratory
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Degrib (NDFD GRIB2 Decoder) |
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Subject: Degrib 1.46
Date: Tue, 16 Mar 2004 12:16:42 -0500 From: Arthur Taylor To: arthur.taylor@noaa.gov Hi everyone, 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 labeling... 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. Regards, Arthur
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