* 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).