Terrain Following in Mission with Distance_Sensor

Hi Theire,
at the Moment I´m a bit confused. When I´m planning a Mission and it comes to hightness then I got two Options:

  1. Relativ to home
  2. Terrain Following

The Documentation says that “Terrain Following” uses the Data of the Map
So, how to set it up when u want to follow the Terrain with your Distance Sensor?
Of cause I put " [EKF2_HGT_MODE]" to 2 for Distance Sensor and “MPC_ALT_MODE” to 1 for terrain following.

Thanks alot in Advance