[Gdal-dev] Re: NetCDF.. the world turned upside-down

[Frank Warmerdam]

Emilio Mayorga wrote:
> "Reversed" y-axis datasets are quite common in netcdf (Ferret, for
> example, pretty much expects that convention -- or at least it did a
> couple of years ago...). It's not required, but it's probably the
> dominant convention. I think it boils down to the common use of matrix
> math in geophysics; the y-axis is seen as positive-up. Unlike the
> GIS/imagery/"raster" world, where the vertical dimension is
> interpreted as increasing from the top down.
> 
> Having gdal_translate and other gdal utilities interpret flipped
> netcdf y-axis automatically (or providing an optional argument) would
> be very useful.

Emilio,

The normal (and in my opinion proper) process for "upside down" datasets
is for GDAL to associate a geotransform with the dataset that indicates
the orientation.  However, I am not adverse to having the netCDF driver
take care of flipping the data internally if Denis would like to address
that.  I believe I did do this in the DODS driver since it was otherwise
very hard to exploit the data in most GDAL based applications.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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