To guide the laser to the correct position I'm using magnetic angle sensors (AS5600L) to feedback the control loops for the motors. For the longitude movement it's easy, just add the magnet on the rotation centre of the laser arm. For the lateral movement it's a little more complicated because the earth globe can freely be rotated around its polar axis...

The solution is to modify the north pole mount and add a magnet that then becomes fixed to the rotation of the earth globe.

The µP will now always know how the earth globe is rotated..