Starting from the regular DEM, the nodes were
transformed by one of the two models into pixel space
and were used as anchor points to bilinearly interpolate
the pixel coordinates of the remaining orthophoto
pixels (the orthophoto had a pixel spacing of 1 m).
Then, the grey values were interpolated by a bilinear
interpolation. The orthophoto was generated for each
spectral channel separately with own software, using
the same parameters, except the input image of course