[gdal-dev] gdalwarp : how many gcp's for -order n?

[Markus Neteler]

(I cc to Helena for TPS insights)

On Tue, Mar 18, 2008 at 9:16 PM, Frank Warmerdam <warmerdam at pobox.com> wrote:
> WolfgangZ wrote:
>  > Hi,
>  >
>  > I know that I've seen it somewhere but I cannot find it any more, can
>  > anyone tell me how many gcp's are needed for transform of order n? How
>  > does -tps work, any literature reference about that option?
>
>  Wolfgang,
>
>   * Note that 2nd order requires at least 6 GCPs, and 3rd order requires at
>   * least 10 gcps.  If nReqOrder is 0 the highest order possible with the
>   * provided gcp count will be used.
>
>   * The GDAL Thin Plate Spline transformer is based on code provided by
>   * Gilad Ronnen on behalf of VIZRT Inc (http://www.visrt.com).  Incorporation
>   * of the algorithm into GDAL was supported by the Centro di Ecologia Alpina
>   * (http://www.cealp.it).
>
>  I don't have any other info on the TPS algorithm.

Yes, we had co-funded the implementation of TPS in GDAL.

Some background info I have found here:
http://www.ncgia.ucsb.edu/conf/SANTA_FE_CD-ROM/sf_papers/fogel_david/santafe.html#radial
http://www.pcigeomatics.com/cgi-bin/pcihlp/GCPWORKS%7CTheory%7CThin+Plate+Spline

and some comments :)
http://lists.osgeo.org/pipermail/gdal-dev/2007-March/012113.html
http://www.gdal.org/gdal__alg_8h.html#245802b88a8126c138d24febe6c9822a

Markus

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Markus Neteler
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