[gdal-dev] Re: Warping an image with both a geotransform and control points

[Jan Hartmann]

Hi all,

This has come up before, but I'm still struggling for an answer. I want 
to rubbersheet an already projected image with control points, so as to 
remove small errors.On a suggestion by Frank 
(http://lists.osgeo.org/pipermail/gdal-dev/2009-February/019775.html) I 
produced a VRT file of the georeferenced image and added control points 
to shift the image 1000m to the right. (see below). However,  GDALWARP 
ignores the control points and returns the original georeferenced image. 
When I remove the georeferencing information, it does use the control 
points, but returns a raw image shifted to the right.

Is it possible to rubbersheet a georeferenced image with control points, 
or am I chasing a red herring?

Thanks,

Jan

<VRTDataset rasterXSize="310" rasterYSize="343">
<SRS>PROJCS[&quot;Amersfoort / RD 
New&quot;,GEOGCS[&quot;Amersfoort&quot;,DATUM[&quot;Amersfoort&quot;,SPHEROID[&quot;Bessel 
1841&quot;,6377397.155,299.1528128000008,AUTHORITY[&quot;EPSG&quot;,&quot;7004&quot;]],AUTHORITY[&quot;EPSG&quot;,&quot;6289&quot;]],PRIMEM[&quot;Greenwich&quot;,0],UNIT[&quot;degree&quot;,0.0174532925199433],AUTHORITY[&quot;EPSG&quot;,&quot;4289&quot;]],PROJECTION[&quot;Oblique_Stereographic&quot;],PARAMETER[&quot;latitude_of_origin&quot;,52.15616055555555],PARAMETER[&quot;central_meridian&quot;,5.38763888888889],PARAMETER[&quot;scale_factor&quot;,0.9999079],PARAMETER[&quot;false_easting&quot;,155000],PARAMETER[&quot;false_northing&quot;,463000],UNIT[&quot;metre&quot;,1,AUTHORITY[&quot;EPSG&quot;,&quot;9001&quot;]],AUTHORITY[&quot;EPSG&quot;,&quot;28992&quot;]]</SRS>
<GeoTransform> -8.5000000000000000e+03,  1.0000000000000000e+03,  
0.0000000000000000e+00,  2.8750000000000000e+05,  
0.0000000000000000e+00,  1.0000000000000000e+03</GeoTransform>
<Metadata />
<Metadata domain="IMAGE_STRUCTURE">
<MDI key="INTERLEAVE">BAND</MDI>
</Metadata>
<GCPList>
<GCP Id="" Pixel="0.0000" Line="0.0000" X="1.000000000000E+03" 
Y="0.000000000000E+00" />
<GCP Id="" Pixel="1000.0000" Line="0.0000" X="2.000000000000E+03" 
Y="0.000000000000E+00" />
<GCP Id="" Pixel="1000.0000" Line="1000.0000" X="2.000000000000E+03" 
Y="2.000000000000E+03" />
<GCP Id="" Pixel="0.0000" Line="1000.0000" X="1.000000000000E+03" 
Y="1.000000000000E+03" />
</GCPList>
<VRTRasterBand dataType="Float64" band="1">
<Metadata />
<ColorInterp>Gray</ColorInterp>
<SimpleSource>
<SourceFilename relativeToVRT="1">test.tif</SourceFilename>
<SourceBand>1</SourceBand>
<SourceProperties RasterXSize="310" RasterYSize="343" DataType="Float64" 
BlockXSize="310" BlockYSize="3" />
<SrcRect xOff="0" yOff="0" xSize="310" ySize="343" />
<DstRect xOff="0" yOff="0" xSize="310" ySize="343" />
</SimpleSource>
</VRTRasterBand>
</VRTDataset>
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