How does the Air2 manage/measure altitude?
Does it measure takeoff location at ZERO, it does it adjust to terrain?
I have a large hill next to our home which is at least 120 feed higher than our back garden. Will the Air2 adjust for these altitude feet and I'm assuming manned aircraft will only fly more than 400ft above the highest location, taking into account for ridges in terrain?
Thanks

Hi,

DJI drones uses a barometric sensor, at start the height is set to zero. This zero height is the reference height during the entire flight.
So take-off from your garden, climb to 125 feet as shown on the fly app screen, close your eyes and fly to that hill....if will fly over it with a clearance of 5 feet.....  ;-)

Haha, people read the aboves too serious....  ;-)  ofcourse i will not fly with my eyes closed!

cheers
JJB

I wouldn't  aim to fly, blind, over a a hill top with a calculated clearance of ONLY 5ft. That is, in my opinion, far too close..
There are 17m trees around my house or on the flight path to my house,  I set an RTH height of 25m or more.

Any change in ambient air pressure in the wrong direction could lead to a 5ft clearance becoming 0ft.

Sean-bumble-bee Posted at 12-31 11:50
I wouldn't  aim to fly, blind, over a a hill top with a calculated clearance of ONLY 5ft. That is, in my opinion, far too close..
There are 17m trees around my house or on the flight path to my house,  I set an RTH height of 25m or more.

Thanks and appreciate the response - I would not do that either. The question was whether the drone would adjust for altitude, but seems not. We usually get up to 300 ft before we move around - we have power lines in the area too which are also on a higher elevation, so right now as a noob, just learning how high things are..

As with most DJI drone, your altitude is shown from the height you took off from, just like you can fly over a cliff and be at -120 feet.

The drone will not adjust its height to follow the terrian UNLESS the ground comes within 50cm.
50cm seems to be a threshold height, try to hover below that height and the drone will more often than not attempt to land or land full stop. If the drone is moving horizontally and slowly enough and the ground is rising in the the direction of flight then the drone will climb to maintain the 50cm clearance, if the horizontal speed if too great the drone may fly into the rising ground.
I have flown my Mavic Mini and a Mavic 2 Pro up the drive at the side of my house, the Mini does it better than the Mavic 2. Fly in the down slope direction and the drone ignores the descending ground and flies horizontally.

To clarify Hawkey's post, the negative height would come about if, after leaving the clliff top and fiying out into 'space', the drone descended below the take off point. My lowest real flight has been from a sea cliff top down to, from memory, in excess of -300ft.
I have seen a substantial 'false' negative height in logs that were started after a disconnection where the disconnection occurred whilst the drone was at height.

Of course an Air 2s with OA switched on may add other behaviours to the melting pot. If you are going to rely on OA then it would be wise to experiment with it......carefully. As a rule I do not fly the Mavic 2 with OA switched on as I normally set the RTH height high enough to clear any obstacles. Experimenting with OA tends to raise the blood pressure a bit.

I’ve had to research before flying from a lower elevation to a higher one. Most of the time I have to take off from a lower elevation due to no suitable take off locations where I can keep line of sight for flight task.

Never trust Google Earth’s elevation as it can be off ~20m which might not sound like a lot but it can mean that you will be risking being too low (unable to clear an obstacle if you lose RC control) or too high (flying above the allowable altitude). I tend to look at detailed terrain maps that have the elevation.

I have a couple of reliable GPS units to ensure the elevation at take off is the same and calculate the difference (since terrain maps can be out by ~5m. I then head to 120m agl, once I get near the elevated location, I start increasing altitude to ensure that I’m at least 80 to 100m above the terrain (while keeping line of sight) and any obstacles but 20m below the maximum flight altitude agl at all times. Then do the reverse when returning home.

Sean-bumble-bee Posted at 2021-12-31 14:32
The drone will not adjust its height to follow the terrian UNLESS the ground comes within 50cm.
50cm seems to be a threshold height, try to hover below that height and the drone will more often than not attempt to land or land full stop. If the drone is moving horizontally and slowly enough and the ground is rising in the the direction of flight then the drone will climb to maintain the 50cm clearance, if the horizontal speed if too great the drone may fly into the rising ground.
I have flown my Mavic Mini and a Mavic 2 Pro up the drive at the side of my house, the Mini does it better than the Mavic 2. Fly in the down slope direction and the drone ignores the descending ground and flies horizontally.

If I understand this correctly, a sudden change in atmospheric pressure can lead to fatal error when flying low. Does anyone know what the maximum  altitude deviation is that one can exepect in a matter of 5 minutes?

Bosduif Posted at 1-1 02:51
If I understand this correctly, a sudden change in atmospheric pressure can lead to fatal error when flying low. Does anyone know what the maximum  altitude deviation is that one can exepect in a matter of 5 minutes?

Air pressure doesn't change that much, that suddenly.
Having a small error in your displayed height shouldn't cause a fatal error.
Flying into terrain causes fatal errors.

If you are literally referring to what you quoted i.e. hovering at 50cm or flying up a slope using the 50cm thing (landing protection) to 'force' the drone to climb, then I do not think sudden changes in atmospheric pressure would cause a crash, the 50cm thing would protect it.  Of course if you were moving quickly then ..........

BUT in general flying ( not close to the ground) then yes a change in atmospheric pressure could be dangerous if you where not watching the drone via either direct line of sight or the 'phone screen', notably if the drone was RTHing with an RTH height that supposedly cleared an obstacle by only a few ft. This is one reason why I aim to clear the trees around my house by 8m or so, it allows for any reduction in air pressure or drift in the barometer reading.

I have seen an answer to the "how quickly can air pressure change" but it was a passing comment in a thread on MavicPilots and I do not remember the thread, sorry. Nor do I remember the answer other than it implied that it could equate to several ft or maybe m of height during a flight.

Bosduif Posted at 1-1 02:51
If I understand this correctly, a sudden change in atmospheric pressure can lead to fatal error when flying low. Does anyone know what the maximum  altitude deviation is that one can exepect in a matter of 5 minutes?

Hi,

Changes in barometric pressure at low heights as follows:
1 mbar change = ~8 meter height change.

As the indicating height is zero`d at takeoff a sudden drop in air pressure (in flight after takeoff) will
indicate a higher height than the actual flying height.

So for short flights (battery endurance) not a problem, or you must fly close to oncoming bad weather.....
cheers
JJB

Labroides Posted at 1-1 04:25
Air pressure doesn't change that much, that suddenly.
Having a small error in your displayed height shouldn't cause a fatal error.
Flying into terrain causes fatal errors.

Thank You for this.

JJB* Posted at 1-1 07:58
Hi,

Changes in barometric pressure at low heights as follows:

Thank you.