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<font face="Times New Roman, Times, serif">Reading the documentation
always helps. The GeomTransform takes the upper left corner as the
origin, not the lower left, as in my math handbook. And the order
of the coefficients is <c b a f e d> With some twiddling of
angles and signs I now can compute the affine transformation of a
scan based on two control points. That means that with the
vrt-file and its geomtransform it is possible to georeference a
scan in real time without warping, at least for a first order
polynomial. Marvelous!<br>
<br>
Thanks for your help.<br>
<br>
Jan</font><br>
<div class="moz-cite-prefix"><br>
On 07/04/2013 09:58 PM, Dmitriy Baryshnikov wrote:<br>
</div>
<blockquote cite="mid:51D5D3DB.1080406@gmail.com" type="cite">Hi
Jan,
<br>
<br>
Do you mean this : <a class="moz-txt-link-freetext" href="http://www.gdal.org/gdal_datamodel.html">http://www.gdal.org/gdal_datamodel.html</a> (Affine
GeoTransform srection) or this
<a class="moz-txt-link-freetext" href="http://www.gdal.org/gdal_tutorial.html">http://www.gdal.org/gdal_tutorial.html</a> (Getting Dataset
Information section)?
<br>
Also, see this:
<a class="moz-txt-link-freetext" href="http://www.gdal.org/classVRTDataset.html#a1531325b71e290b90c8d9cc88bce6c2b">http://www.gdal.org/classVRTDataset.html#a1531325b71e290b90c8d9cc88bce6c2b</a><br>
<br>
Best regards,
<br>
Dmitriy
<br>
<br>
04.07.2013 20:12, Jan Hartmann пишет:
<br>
<blockquote type="cite">I'm struggling with the order of the
Geotransform section in a vrt file. I would like to rotate an
image, and computed the six parameters for the affine
transformation. I can transform points exactly, using the
following formula:
<br>
<br>
x2 = a.x1 + b.y1 + c
<br>
y2 = d.x1 + e.y1 + f
<br>
<br>
Can anyone tell me what the order is in the GeoTransform section
of the VRT-file?
<br>
<br>
<GeoTransform> c a b f d e </GeoTransform>
<br>
<br>
results in an image somewhere in the neighbourhood, but mirrored
and translated. What is the order of the parameters a-f?
<br>
<br>
Jan
<br>
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</blockquote>
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