[Gdal-dev] GeoTiff tag Question

[Frank Warmerdam]

Reinaldo Escada Chohfi wrote:
> Heloo List,
> 
> Could anyone let me know how to get the right X and Y values to go from
> 
>    Tagged_Information:
>       ModelTransformationTag (4,4):
>          0.50                     -9.61303488e-006 0                
> 4679893.77
>          -7.88540724e-005 -0.50                    0                
> 7913730.85
>          0                0                1                0
>          0                0                0                1
>       End_Of_Tags.
> 
> to
> 
>    Tagged_Information:
>       ModelTiepointTag (2,3):
>          0                0                0
>          X?              Y?               0
>       ModelPixelScaleTag (1,3):
>          0.50           0.50            0
>       End_Of_Tags.
> 
> Thanks in advance,

Reinaldo,

If you were to change the small rotational coefficients to zero you would
get:

    Tagged_Information:
       ModelTiepointTag (2,3):
          0                0                0
          4679893.77       7913730.85       0
       ModelPixelScaleTag (1,3):
          0.5              0.5              0
       End_Of_Tags.

Note that this is not an exact representation.  An exact conversion
is not possible since the tiepoint+pixelscale method can't represent
rotation.

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