Tests
This should not happen. Seems I got the rotation of the directions wrong.
Edit: not really a bug. The tests are not written with possible map rotation in mind: If one sets slope/direction then on the map the slope/direction might be rotated. In order to fix this, the actual slope/direction have to be queried and used.
Edit2: For slopes this can be corrected. However, the coordinate transform for grid points to raise/lower is wrong.