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Implement Molodensky-Badekas transformation #1160
This is a variation of Helmert 7 parameters where the rotation is not applied regarding the Earth centre, but with a reference point (in cartesian space). So X,Y,Z input coordinates are expressed regarding this Xp,Yp,Zp evaluation point, the Helmert rotation is applied, and then we re-add Xp,Yp,Zp, and then the translation terms of Helmert. So the existing PJ_helmert could just be enhanced with those Xp,Yp,Zp coordinates (one can convince oneself easily that when Xp=Yp=Zp=0, this is standard 7-parameter Helmert). Of course this is better documented in EPSG guidance 7.2
My reasoning for including this in PJ_helmert is that it is should be just a matter of doing something like
(by the way the use of lpz.lam and lpz.phi here is super confusing as we are in the cartesian space in input space)
I am aware that the math is simple this way. I am just worried about the growing number of parameters in Helmert.
The Molodensky-Badekas only uses the first 7 Helmert parameters, right? We could make a
I think this will also communicate better what transformation is performed.
I agree. Feel free to fix it by adding a