Georeferencing question

[Frank Warmerdam]

On 1/4/06, Gambin Dejan <Dejan.Gambin at pula.hr> wrote:
> Hello,
>
> I know it probably belong to gdal list but I'll give it a try here..
>
> I am trying to georeference my scanned paper maps. I have tried using
> QGIS Georeferencer plugin, it works ok for linear transformation but the
> resulting georeferenced raster map does not fit vrey well, probably
> because of deformations etc. I have tried using Helmert transformation
> but unfortunatelly QGIS crashes (running on Windows).
>
> So I tried using gdal_translate and gdalwarp. I took the corner
> coordinates (only UpperLeft and BottomRight for testing) and run
> "gdal_translate -gcp 0 0 5409006.4226 4970689.5864 -gcp 7590 5931
> 5409806.0064 4970064.7150 025-k.jpg 025-k-translated.jpg -of JPEG". But
> setting output format to JPEG results in unchanged output image.
>
> I suppose it is normal and gdal_translate cannot create gc points in
> this way? Do I have to use default TIFF output format?

Gambin,

Only a few formats support GCPs.  You would need to write output
to a format like TIFF or VRT.

> What to do next with gdalwarp? What type of transform and resampling to
> use?

If you succeed in attaching a fair number of GCPs (at least more
than the 3 defining an affine transform) then you could try the
-tps switch to use thin plate splines instead of simple polynomials.
It may give better results.

Best regards,
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