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20050126: 20050124: Gempak file format description

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  • Subject: 20050126: 20050124: Gempak file format description
  • Date: Mon, 31 Jan 2005 16:33:50 -0700
Sherrie,

The creation of the GEMPAK grid file is done through the DM_
routines.

If you have gotten as far as GR_MNAV, then the next step is to 
get an analysis block through GR_MBN2, then create the grid file
through GD_CREF.

The analysis block can be filled with missing values.

There is a routine $NAWIPS/unidata/programs/gdtopo/gdtfil.f that
is a simple example for creating a grid file for a topography
data set (simple CED projection and angles). The routine GDTWDR 
calls the GD_WPGD routine to write a packed grid the number of
bits passed to the routine to represent the data. The gdtopo program
might help to follow the steps for writing a grid to a file.

The DM_ library contains the data management access routines that
handle byte order reading as well as the general layout of
the data management file. In general, DM is hiding some of the
details such as determining if the byte order of the data is the same
as the platform you are reading/writing the data (eg ENDIAN order).

The text of the programmers guide to gemlib is old (but so is the DM
library), which you will find in $GEMGTXT/dmlib.txt which gives a brief
overview to DM.

Steve Chiswell
Unidata User Support







>From: Sherrie Fredrick <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200501262125.j0QLPXv2016989

>Hi Steve,
>
>   What I have are binary files that contain radar data.  These files
>are output from another program called CEDRIC.  What I would like to
>do is convert the binary data files into a Gempak grid file, but I 
>don't know how the Gempak grid files are formated.  I know they have
>a navigation block and I have been able to create that by reading 
>the GR_MNAV code to see what is expected, but I don't have a clue as
>to how the data is layed out in the file.  
>
>
>                         Thanks,
>                         Sherrie
>
--
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