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Re: another netcdf/grid question (fwd)


===============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
address@hidden             WWW: http://www.unidata.ucar.edu/
===============================================================================

---------- Forwarded message ----------
Date: Wed, 7 Apr 1999 12:50:24 -0600
From: Steve Chiswell <address@hidden>
To: Robb Kambic <address@hidden>
Subject: Re: another netcdf/grid question (fwd)


The quasi-thinned AVN grids are on grid 255, but the RUC2 grid
is 236/255 (depending on what Cray runs the model).
The 255 code means you have to use the GDS information in the grib
file to determine the type of grid (Octet 6).

The avn on grid 255 is thinned, and must be interpolated to the Lat/lon
grid that is in the CDF file. The RUC2 grid is type 3 (Lambert COnformal).

To determine what projection each grid 255 uses, see table 6 in the grib
description document for the GDS. Then after determining what projection
is used, use table D for the appropriate grid to determine what the
meaning of the octets in the GDS represent. 

If your question is in regard to the cdl, as to what you can assume for
the defining projection angles based on grid type, then that should 
follow from the NUWG convention.

Steve Chiswell
Unidata User Support

On Wed, 7 Apr 1999, Robb Kambic wrote:

> Chiz,
> 
> I would believe Tom is correct that for grid 255 the it's a lat/lon type
> grid.  But since I'm no grid expert could you confirm that's true.
> 
> Thanks,,
> Robb...
> 
> I don't have the grid manual at home
> 
> ===============================================================================
> Robb Kambic                              Unidata Program Center
> Software Engineer III                    Univ. Corp for Atmospheric Research
> address@hidden                   WWW: http://www.unidata.ucar.edu/
> ===============================================================================
> 
> ---------- Forwarded message ----------
> Date: Tue, 06 Apr 1999 17:06:14 -0500
> From: Tom Whittaker <address@hidden>
> To: address@hidden
> Cc: Don Murray <address@hidden>
> Subject: another netcdf/grid question
> 
> Robb:
> 
> In looking over an AVN grid that Don sent me, I find the grid
> code is 255, but the grid_type_code is 0 (indicating a lat/lon
> grid).  Is this pretty much the standard way of doing things? 
> That is, if the grid code is 255, then I can use the
> grid_type_code to indicate what parameters should be available in
> the file for navigation?  (falls into that "can I safely
> assume..." category...)
> 
> Thanks.
> 
> tom
> 
> -- 
> Tom Whittaker (address@hidden)
> University of Wisconsin-Madison
> Space Science and Engineering Center
> Phone/VoiceMail: 608/262-2759
> Fax: 608/263-6738
> 
>