[Gdal-dev] GMT & GDAL Geotiff grid registration

Frank Warmerdam warmerdam at pobox.com
Fri Nov 18 16:07:20 EST 2005

On 11/18/05, Rich Signell <rsignell at usgs.gov> wrote:
> Yes.  The question is what to do with that information, I guess.
> Since GeoTIFF can be specified as  "Area" or "Point", one approach
> would be to write the appropriate value for the GeoTIFF based on
> the "node_offset" attribute on the "z" variable.

Rich / J. Luis,

Whether a GeoTIFF indicates the data is point or area
related, the georeferencing information always deals with
it as an area.  The (0,0) location is the top left corner of
the top left pixel area.   The point/area distinction is only
kept as metadata.  In GDAL pixels are always georeferenced
as "area", and so for GMT we just need to recognise the case
where the georeferencing has to be offset.

I have grabbed the files and will try to adjust them and update
Bug 796 which J. Luis is correct in pointing out I have ignored for
a long time.   I think I jumped on the topic this time mainly
because I had a vague sense that it had come up recently.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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