I've seen a few old posts saying that Active track follows you down hill but I tried it recently and it tracked me correctly but did not lower its altitude as I walked down the hill, it appreared to stay at the original height above home point. Maybe I have to set Home Point to "Controllers position"?                     
                 

You might bee thinking about Terrain Follow Mod Page#22 in MP manual.
That will not follow you down hill just up and max altitude 13m.