You are standing on level ground and want to fly your bird over the building in front of you that is 100 ft high. Let's say maybe something like a large covered sports dome. On the other side of the building, you lose contact. RTH is engaged. The bird does its thing and flies to 20 meters, checks bearings and returns home. Crash! The bird just found the side of the building. How to prevent this? One way could be to record various positions and altitudes while in flight. So the bird should know that returning home via those points is safe. Like having its own waypoint system. The next question is, can the bird return home in the allotted time the battery has remaining?