[gdal-dev] Datum Shifts with OSR.CoordinateTransform

[Armin Burger]

Steve

In newer versions of the WKT definition there is sometimes a TOWGS84[...] tag included which contains the 7 shifting parameters, but I don't know if this is already a standard notation and if GDAL automatically takes this into account when found.

What should normally work is to use the Proj4 notation which includes the tag 
  +towgs84=.....

and then define the projection via the method
  ImportFromProj4()

armin

-------- Original-Nachricht --------
> Datum: Mon, 9 May 2011 20:07:23 -0700 (PDT)
> Von: srweal <srweal at gmail.com>
> An: gdal-dev at lists.osgeo.org
> Betreff: [gdal-dev] Datum Shifts with OSR.CoordinateTransform

> Hi all,
> 
> I'm using the C# wrapper and GDAL/OGR binaries from Tamas' repository
> (http://vbkto.dyndns.org:1280/sdk/) and am trying to do coordinate
> transformation that includes a datum shift on a geometry.  
> 
> I'm wanting to understand how I can control what shift parameters are used
> when calling the MyGeometry.Transform(MyTransform) method.  
> 
> I have been creating the CoordinateTransform by using the basic
> constructor
> (i.e. new CoordinateTransform(SourceSR, TargetSR)) but this doesn't give
> me
> any control over the shift.  Do I need to define the shift parameters on
> the
> actual SourceSR and TargetSR?  If so, how is this best done.
> 
> Currently I'm creating the SourceSR via the ImportFromWkt() method and
> obtaining the WKT from spatialreference.org.
> 
> Thanks for any advice, examples or links you can provide with more
> information.
> 
> Steve 
> 
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