Maximum altitude settings

[GKomar]

If I set my M2P to a maximum altitude of 300ft, and fly past the edge of a 500ft cliff, will it descend 200ft until it's 300ft above the floor of the valley?

 

[msinger]

After flying over the cliff, the Mavic will continue to fly at the same altitude until you manually increase or decrease it. Also, the height (altitude) displayed at the bottom of DJI GO won't change since that value is the altitude over top of the takeoff point. You won't hit the max altitude until the height displayed at the bottom of DJI GO reaches your max altitude setting.

 

[brett8883]

After flying over the cliff, the Mavic will continue to fly at the same altitude until you manually increase or decrease it. Also, the height (altitude) displayed at the bottom of DJI GO won't change since that value is the altitude over top of the takeoff point. You won't hit the max altitude until the height displayed at the bottom of DJI GO reaches your max altitude setting.

I think he’s asking if the max altitude applies to a negative altitude as well as a positive altitude. Like if the max altitude is set at 300 feet will it be restricted to a -300 feet as well? I think so but I am not positive.

I do know that it can’t possibly know that it’s 300 feet above the the bottom of the cliff so it will either stop at -300 feet or go all the way down.

Anybody know?

 

[sar104]

I think he’s asking if the max altitude applies to a negative altitude as well as a positive altitude. Like if the max altitude is set at 300 feet will it be restricted to a -300 feet as well? I think so but I am not positive.

I do know that it can’t possibly know that it’s 300 feet above the the bottom of the cliff so it will either stop at -300 feet or go all the way down.

Anybody know?

Firstly - that's not what he is asking. He is asking if, when the aircraft finds itself at 500 ft AGL above the floor of the valley when its maximum altitude is set to 300 ft, will it immediately descend 200 ft to remain within 300 ft AGL. Since the altitude limit is relative to the takeoff location, not the ground under the aircraft as it flies, the answer to that is no, it won't descend. Additionally, unless it is within 30 ft or so of the ground and therefore within the range of it's downward VPS system, the aircraft has no way of knowing it's altitude AGL because it doesn't have a digital elevation model on board - it only knows barometric and GPS absolute and relative altitudes (relative to takeoff point).

As for the question that you are asking the answer is also no - the altitude limit is the maximum altitude above the takeoff point. It is not the minimum altitude below the takeoff point. There is no set minimum altitude.

 

[GKomar]

Thank you, sar104. That's the answer to my question.

 

[GKomar]

However, if I landed at the base of this 500ft cliff, shutdown and restarted, I wouldn't be able to return to my original starting point, at the top of the 500ft cliff. Correct?

 

[brett8883]

Firstly - that's not what he is asking. He is asking if, when the aircraft finds itself at 500 ft AGL above the floor of the valley when its maximum altitude is set to 300 ft, will it immediately descend 200 ft to remain within 300 ft AGL. Since the altitude limit is relative to the takeoff location, not the ground under the aircraft as it flies, the answer to that is no, it won't descend. Additionally, unless it is within 30 ft or so of the ground and therefore within the range of it's downward VPS system, the aircraft has no way of knowing it's altitude AGL because it doesn't have a digital elevation model on board - it only knows barometric and GPS absolute and relative altitudes (relative to takeoff point).

As for the question that you are asking the answer is also no - the altitude limit is the maximum altitude above the takeoff point. It is not the minimum altitude below the takeoff point. There is no set minimum altitude.

Yea I misunderstood the question my bad

 

[msinger]

if I landed at the base of this 500ft cliff, shutdown and restarted, I wouldn't be able to return to my original starting point, at the top of the 500ft cliff. Correct?

You likely wouldn't want to do that since it would reset the home point to that new location. However, you could still manually fly back to the previous home point if the remote controller is still connected to the Mavic.

 

[sar104]

However, if I landed at the base of this 500ft cliff, shutdown and restarted, I wouldn't be able to return to my original starting point, at the top of the 500ft cliff. Correct?

You likely wouldn't want to do that since it would reset the home point to that new location. However, you could still manually fly back to the previous home point if the remote controller is still connected to the Mavic.

Actually the barometer is reset on takeoff and landing (see the event stream entries below), and so the 300 ft limit would now be below the original takeoff point. Without increasing that limit you would not be able to ascend back to the top of the cliff.

[L-NS][AHRS] reset baro just after takeoff​

[L-NS][AHRS] reset baro just after land​

​

 

[msinger]

Actually the barometer is reset on takeoff and landing

I think you have to actually stop and start the motors for the home point and height to be reset. But, you’re right about needing to increase the max altitude in order to make it back to the top.

 

[kilomikebravo]

However, if I landed at the base of this 500ft cliff, shutdown and restarted,

I think you missed that part, Mike and obviously, as SAR indicated, he couldn't get back to the takeoff point in this scenario.

 

[GKomar]

Sar104, and all:
Thanks for the information. Well put, well received.

 

[Gonerafting]

I also appreciate this Post, since I had the same question in regard to flying over a lake I live by which is maybe 65 feet below where the takeoff will be at my house and using Litchi Waypoints. My concern was on it's return home would it be at a lower altitude than set by the takeoff point. I did not want to assume it would not safely fly over trees, although the altitude set should have been good enough if the altitude would have been set to the lower elevation.

 

[brett8883]

I also appreciate this Post, since I had the same question in regard to flying over a lake I live by which is maybe 65 feet below where the takeoff will be at my house and using Litchi Waypoints. My concern was on it's return home would it be at a lower altitude than set by the takeoff point. I did not want to assume it would not safely fly over trees, although the altitude set should have been good enough if the altitude would have been set to the lower elevation.

Always set your RTH altitude so that it’s high enough to avoid any obstacles using the take off point as the reference point. RTH altitude is always the height above the take off point even if you fly below it during flight.

Example. If you take off from the top of a cliff and your RTH height is 50 meters. If you fly down the cliff 10 meters and press RTH the drone will fly up 60 meters so that it is 50 meters above the take off point before coming home.

 

[sar104]

I also appreciate this Post, since I had the same question in regard to flying over a lake I live by which is maybe 65 feet below where the takeoff will be at my house and using Litchi Waypoints. My concern was on it's return home would it be at a lower altitude than set by the takeoff point. I did not want to assume it would not safely fly over trees, although the altitude set should have been good enough if the altitude would have been set to the lower elevation.

As @brett8883 mentioned it will still treat the set RTH height as above takeoff. But since you mentioned Litchi, it is worth also noting that unless you are using AGL mode, Litchi does have a minimum altitude limit for relative waypoints.