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

[Wolfgang]

Markus Neteler schrieb:
> (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
>
>   
many thanks for the information!

Kind regards
Wolfgang