Visual positioning and barometer while flying above water

[Jwelz]

Sufficiently clear water can act like glass and your Mavic may be seeing the river or lake bottom and not the surface. If the craft was heading towards deeper water, it may have been following the ground surface beneath the water. The bottom infrared sensors may get reflected signals from both the water upper surface as well as the bottom also yeilding conflicting results. The acoustic sensors on the older Mavic Pro tended to give a clear single range to water surface when smooth and flat but a rippled surface could yeild interference reinforcement in the reflections that could provide an accurate closest distance and several further distances based on the wave/ripple peak to peak distance. Signal strength is weakened more by 'steeper' waves that reflect the signal obliquely rather than returning to the receiving transducer.

Another problem was when the waves tend to move in a direction or there are objects drifting on the surface with current or wind, the optical position hold functionality will tend to cause Mavics to drift with the moving surface. More than a few Mavics have followed a river into the side of a bridge while their sensors told them they were holding a static position.

 

[afarkas]

Exactly. This is a deep explanation of loosing altitude at acceleration

I'm not really qualified to answer this, I'm not an aerospace engineer but did sleep at a holiday inn last year. This is my thinking. Whether accelerating or traveling at a set speed, the aircraft does pitch forward for that purpose. I think that is to build or continue forward speed. At the same time, the tilt of the aircraft should cause a down force, created by traveling at speed, on the top front, rear of the aircraft. And, at the same time, the bottom sensors and barometer are trying to keep the aircraft at the required altitude having to increase or decrease the power at the props to attain that. Then you have the tolerances of the sensors, or any of the electronics, altitude, wind speed and direction, which then throws other problems/possibilities into the mix. While your logic is not FUBAR'd there are many other things that have to be considered. I'm trying to figure out whether to try flying over water at around 1 to 2 feet and found during my first land test that the M2P will dive straight into the ground at that altitude, at least once.