Re: Need advice on storing lat-lon data

All,

My apologies that the CF web site that John referenced below is currently
out of service due to our web server being hacked.  It will (I hope) be
returned to service quickly.

Brian


On Mon, Oct 06, 2003 at 04:20:24PM -0600, John Caron wrote:
> Matthew Hanna wrote:
> 
> >Hello!  Please forgive my lack of technical terminology and such.  I 
> >am new to this NetCDF stuff.  I am trying to write a utility to 
> >convert our in-house data files used for storing data about water 
> >velocity, temperature and salinity to NetCDF.  The data is organized 
> >in grids.  My employer has asked me to keep the NetCDF file compatible 
> >with Navo NetCDF which follows the COARDS convention.  I have done 
> >well with the regular grids until now.  My problem is that the grid I 
> >am now considering is not a regular grid.  Before, I would store the 
> >latitude numbers in a coordinate variable and the longitude in another 
> >coordinate variable.  The grid was formed by intersecting these 
> >coordinates.  Now my grid is irregular -- few, if any, longitudes or 
> >latitudes are the same.  They still form a grid but not a nice easy 
> >grid.  How should I store something like this?  If you need better 
> >details please let me know and I will try to be more specific.
> >
> > 
> >
> >Thanks!
> >
> >Matthew Hanna
> >
> Hi Mathew:
> 
> The COARDS conventions are restricted to lat/lon 1D coordinate 
> variables. Grids that are on a projection coordinate system (eg Lambert, 
> Stereographic, etc) need 2D lat/lon coordinates, eg lat(x, y), lon(x,y). 
> Typically, they are still regular on the projection plane. The best 
> thing is to include everything in the netcdf file: 1) the "natural" 
> projection coordinates as 1D coordinate variables, 2) the 2D lat/lon 
> coordinates, and 3) the projection info that maps between the two.
> 
> The CF Conventions extend COARDS to handle, among other things, 
> projection coordinates. I would recommend that you use them if possible:
>  http://www.cgd.ucar.edu/cms/eaton/cf-metadata/
> They are a bit daunting in length, but i would be happy to help if you 
> want to send me more info.
> 
> 

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