[Geotiff] User defined datum: Transformation parameters

Frank Warmerdam warmerdam at pobox.com
Tue Feb 26 13:32:54 PST 2008

Christian Zietz wrote:
> Hi,
> as far as I know there exists no official way to store transformation
> parameters (e.g. for a 7-parameter Helmert transformation) for a user
> defined datum in a GeoTIFF.
> So, before I go ahead and implement a solution using a private key ID:
> Did someone do this before? Is there an unofficial specification I can
> adhere to?


I am not aware of any way to store preferred datum shifting parameters
in GeoTIFFs in a standardized way.  If you prepare one, it might be
worth considering writing it up and offering it as an extension.

In theory it should be possible to pick a geotag # for it, and store it
within the geotiff info though I'm not aware of any other multi-value
floating point values handled as geokeys.

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    | President OSGeo, http://osgeo.org

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