msinger said:
There's no need to turn off Vision Positioning unless you're flying within 42 feet (13 meters) of the surface of the water.
Not sure if it's 13 meters or 10,
@msinger? FIne point, just recall something different from the manual, but too lazy to look it up
Anyway, the reason for this, people, is because of the reflective nature of water. In fact, VPS should be disabled over any highly reflective surface.
The reason for this is how VPS works... It detects movement in the visual field. Problem with reflective surfaces is when the aircraft moves, the reflection moves in lock step, so to the Mavic it looks like it isn't moving. To make matters worse, any change in attitude (roll/pitch) WILL look like translation to the downward cameras -- the image suddenly flies off in the opposite direction to the roll/pitch.
All of this just throws the positioning logic into complete fits, and aircraft have been known to fly off completely out of control, unresponsive to stick input, as the autonomous systems try to stabilize position based on a moving image.
Bottom line: Just turn VPS off if you're going to be flying over water, don't get caught up in what altitude, etc. You're not going to be landing on the water anyway, and extreme precision positioning is very rarely called for in these situations anyway. GPS can do a good enough job holding position in these situations.