Pick LPS coordinate from 3d model

I’ve loaded up an STL file that should be in LPS coordinates.
I’m able to place spheres on the 3d mesh with:

picker = vtk.vtkCellPicker()
picker.Pick(x, y, 0, renderer)
p = picker.getPickPosition()

Then p is the correct location to place a coneActor to denote the point. But I want to coordinate in LPS(the coordinate system the stl is based on) too. It looks like vtk 0,0,0 is placed at the center of the model so I need that to be translated to the absolute LPS Position?