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Degrib: Appendix

Brief explanation of the directory structure:

(Note: When I refer to "/degrib/", on MS-Windows I typically mean: "c:\ndfd\degrib20\" or "/cygdrive/c/ndfd/degrib20/".)

Path Purpose
/degrib/arcview Contains ESRI specific files to assist with map projections, and legends.
/degrib/bin Contains the main programs (degrib, tkdegrib, etc).
/degrib/data Is the default location for GRIB2 data.
It also contains geographic data for the imageGen program.
/degrib/docs Contains project documentation, including man pages, and some papers.
/degrib/lib Contains extra libraries for the GUI tkdegrib
/degrib/output Is the default output location for tkdegrib.
It also contains the images created by imageGen program.
/degrib/test Contains any test scripts and answer data.
/degrib/src Contains all the source code used to create degrib.
Path Purpose
/degrib/src/zlib Library: Provides gzip compression. (http://www.gzip.org/zlib/)
/degrib/src/libpng Library: Provides png compression. (http://www.libpng.org/pub/png/libpng.html)
/degrib/src/jpeg2000 Library: Provides jpeg 2000 compression. Based on a subset of the jasper library. (http://www.ece.uvic.ca/~mdadams/jasper/)
/degrib/src/grib2lib Library: Provides the ability to read GRIB2 messages. g2libc-1.0
/degrib/src/emapf-c Library: Provides Lambert Conformal map projection capability. This is a newer copy than the "official" one. (http://www.arl.noaa.gov/HYSPLIT_cmapf.php)
/degrib/src/netcdf Library: Provides netcdf interface. (http://www.unidata.ucar.edu/packages/netcdf/)
/degrib/src/degrib Source code for degrib, tcldegrib and tkdegrib. (http://weather.gov/mdl/degrib/)

Brief description of output files:

Type Description
*.txt A '|' delimited ASCII file, containing information ("meta data") about what is in the grids. It is intended to be human readable without requiring previous knowledge of the "WMO GRIB2 Document".
*.is0 An ASCII file, containing a dump of the various values in the arrays returned by the grib2_unpacker library. It is intended for debugging purposes.
*.shp, *.shx, *.dbf The combination is known as a "shape file". The .shp file contains the spatial (Lat/Lon) informtaion, the .shx is an index into the .shp file for faster redraws, and the .dbf contains the actual data.
*.flt, *.tlf The .flt file contains the grid in an NxM 4 byte (octet) float file, which starts in the upper left corner, traverses a row, then starts again on the left. The .tlf file is similar, except it starts in the lower left. Typically the .tlf file (aka mosaic file) is "Least Significant Byte first".
*.dat The data cube file (.dat) is very similar to the .flt file, except that it contains multiple messages. It is typically used in conjunction with the .ind file to create a flat file database for fast (CGI) access to the uncompressed form of the NDFD. Note: One idea for the future is to use the .dat file in GrADS instead of the .flt file.
*.ind The .ind file is an index file that contains some meta data, but also refers to a set of .flt files, or a single data cube file (.dat). The purpose of the index file is to allow fast (CGI) access to the uncompressed form of the GRIB data. The index file combined with the .flt files or single .dat file forms a simple free flat file database.
*.hdr An ASCII file, used by ESRI Spatial Analyst to assist it with using the .flt file. Contains information such as the number of points in the X and Y directions, what the missing value is, and whether the data is stored "Most Significant Byte first" or "Least Significant Byte first".
*.ctl An ASCII file, used by GrADS to assist it with using the .flt file. Contains information such as the map projection, the number of points in the X and Y directions, what the missing value is, and whether the data is stored "Big Endian" or "Little Endian".
*.csv An ASCII file consisting of "X, Y, lat, lon, value" for each grid cell in the grid.
*.nc The grid stored as a "NetCDF" file. See the "NetCDF Specifications" for more information.
*.grb The grid or a subgrid stored as a GRIB2 file.
*.ave An ASCII file containing an ESRI ArcView avenue script, which sets up a map projection to match the shape of earth and map projection specified in the GRIB2 message.

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    Page last Modified: April 16, 2010.
Degrib Questions? Arthur Taylor
NDFD Questions? nws.ndfd@noaa.gov
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