[Geotiff] Affine Transformation

[Gianni Rossi]

Hi All,

 

I'm new both to this mail-list and to GeoTIFF too.

 

Nevertheless, I'm developing a Cad application which allows the user to pick
a desired number of points in a TIFF raster image (thus the application
retrieves their raster coordinates) and inputs their corresponding model
coordinates. Then the application performs an affine transformation between
the two systems and calculates the 4 parameters: X translation, Y
translation, scaling factor, rotation angle.

 

So my question is: how do I store this georeferencing data into the original
TIFF file so that it becomes a GeoTIFF file? 

 

Looking at some documentation, it seems that ModelTransformationTag would do
the case, but unfortunately I could not find specification on how to
transform my (affine transformation) parameters into its arguments.

 

Another option for me could be to create a TFW file, but also in this case I
don't understand how to convert my affine transformation 4 parameters into
the TFW values. Also, Cad software, such as AutoCAD, seems to ignore the
second and third lines of a TFW (X/Y rotation).

 

Any help to lead me in the right direction would be greatly appreciated,
thanks in advance.

 

Gianni Rossi

Tecnobit S.r.l.

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.maptools.org/pipermail/geotiff/attachments/20090308/0fc3ff56/attachment.htm