I have always wanted to test out how Good the Active Tracking of the Mavic Pro is in the 3 dimensional space using another drone. Today I had the chance to try out with my buddy on a 550 size hexacopter.
I had some difficulty trying to get the Mavic to recognise the hexacopter as it is rather small if I keep a safe distance. After a few trial and error, I managed to move in close enough to let the Mavic lock on. Tracking is generally smooth, and the obstacle avoidance system ensures the Mavic is kept at a safe distance from the subject. I could observed the Mavic did some emergency braking when the subject made a sudden slow down in speed. However, the Mavic will lose track when the subject makes a change in altitude to disappear from the screen.
In conclusion, I will say the Active Tracking is usable, but not in all situation. Especially, if the subject moves very randomly or moves up and down beyond the vision range.