Maximum Hieght Question

[andyd01275]

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I did this Shoot yesterday, and I reviewed the flight data when I got back and found that I had gone over 400ft by 7ft. In the app I have it set to 400ft max, so my question is why would it of flown over the max hieght and especially as I was at see lever as you can see in the footage.
Thanks in advance, AndyD

 

[Meta4]

I did this Shoot yesterday, and I reviewed the flight data when I got back and found that I had gone over 400ft by 7ft. In the app I have it set to 400ft max, so my question is why would it of flown over the max hieght and especially as I was at sea level as you can see in the footage.

That's sounds unusual.
Perhaps the flight data would have some clues?
That you were sea level wouldn't make any difference as the Phantom can't tell that.

To check the flight data, go to DJI Flight Log Viewer - Phantom Help
Follow the instructions there to upload your flight record from your phone or tablet.
Come back and post a link to the report it gives you.

 

[andyd01275]

Thanks mate, will do when I get a moment. AndyD

 

[Sburke91]

Isn't the 400' limitation heigh above ground, not height above starting point?

 

[BuffaloAir]

Thanks for the discussion guys. I've been taking altitude reporting for granted. While flying my MA, it's been my experience altitude recording starts with take off point as ground zero. If Im standing on the edge of a ravine and I lift the drone up 10 ft, my MA reads10 ft of altitude. If I stay level and now fly out over the ravine my altitude read out continues to read 10ft although the bottom of the ravine is now way below the drone, lets say 100 ft.. I have always assumed the drone was reading pressure altitude. Am I all wet?

 

[andyd01275]

Now you guys have really confused me.

 

[Congoblue]

Altitude readout is above takeoff point. I have mavic pro and I have seen it go a couple of metres over the set height sometimes if you zoom up to max altitude.

 

[Meta4]

Thanks for the discussion guys. I've been taking altitude reporting for granted. While flying my MA, it's been my experience altitude recording starts with take off point as ground zero. If Im standing on the edge of a ravine and I lift the drone up 10 ft, my MA reads10 ft of altitude. If I stay level and now fly out over the ravine my altitude read out continues to read 10ft although the bottom of the ravine is now way below the drone, lets say 100 ft.. I have always assumed the drone was reading pressure altitude. Am I all wet?

Your drone uses a barometer to measure air pressure and displays a relative aititude based on this.
Home = zero and all heights are relative to the home point.

 

[InvisibleName]

I’m sure it’s height above or below your takeoff point. I recently flew in the Lake District & having taken off from the side of a hill, I flew down & had negative altitude readings

 

[Canuk]

As far as I know it reads from Home point . That is ground zero . These drones have no way of knowing if you fly them over a river valley . They are not that smart yet . [emoji41]

 

[andyd01275]

I’ve just spoken to DJI support and they say that what you set in the app as the altitude, should not allow the drone to fly any higher. But they don’t seem to have answer and escalate my question, so will see what comes back.

 

[BuffaloAir]

The regulation of 400 ft assumes AGL (above ground level) and that the drone is directly above the starting point. That's why, you can legally, if airspace classification allows, go 400 ft above the building over which you are flying.

When flying manned aircraft and taking off from an airport that is 500 ft above sea level (pressure altitude) you are given a barometric pressure to which to set your altimeter. ATIS or ground control or tower gives you an altimeter setting (barometric pressure reading) to set your altimeter. Let's say they say "altimeter is 29.95". You dial 29.95 into your altimeter and the altimeter should read 500 ft., however you are still 0 ft AGL (Above ground level). You take off from the airport and climb to 1000 ft on your altimeter you are now 500 ft AGL but 1000 ft pressure altitude.

What I have assumed is that my MA (somehow) records the barometric pressure out side at take off then sets my altimeter to 0 and flies from there. I may be all wet, that's why I'm interested in this discussion.

 

[andyd01275]

If it’s the gps that works out the height you are at, then it should be able to work it out that it’s from your takeoff point. If you are at the top of a cliff that’s 500ft drop and you are at the top and takeoff and go 100ft up and then out over the cliff edge you should still be at 100ft not 600ft. Otherwise we are all breaking the law [emoji853]

 

[BuffaloAir]

andyd01275, that is exactly what everyone has said. My question is how does it do that.

 

[BuffaloAir]

I have always assumed that the 400 ft AGL rule for drones was established based on the manned aircraft MINIMUM Altitude (in non-built up and un-populated areas) of 500 ft AGL.

 

[andyd01275]

It’s the U.K. and max is 400ft.

 

[Congoblue]

Mavic Pro uses barometric sensor to determine height, not gps. I would have thought Air would be the same. GPS height reading would not be accurate enough.

 

[beachcombing]

I did this Shoot yesterday, and I reviewed the flight data when I got back and found that I had gone over 400ft by 7ft. In the app I have it set to 400ft max, so my question is why would it of flown over the max hieght and especially as I was at see lever as you can see in the footage.
Thanks in advance, AndyD

Are you sure you have the maximum altitude set to 400 feet and not 400 meters?

 

[Meta4]

I have always assumed that the 400 ft AGL rule for drones was established based on the manned aircraft MINIMUM Altitude (in non-built up and un-populated areas) of 500 ft AGL.

It's a common misconception that airplanes have to stay above 500 ft but this is not true.
There are many situations where planes can legally fly lower than 500 ft.
Here is the US FAA rule relating to this. Note C & D

§ 91.119 Minimum safe altitudes: General.
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
(d) Helicopters, powered parachutes, and weight-shift-control aircraft. If the operation is conducted without hazard to persons or property on the surface—
(1) A helicopter may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section, provided each person operating the helicopter complies with any routes or altitudes specifically prescribed for helicopters by the FAA​

 

[SaOuGenLa]

Thanks for the discussion guys. I've been taking altitude reporting for granted. While flying my MA, it's been my experience altitude recording starts with take off point as ground zero. If Im standing on the edge of a ravine and I lift the drone up 10 ft, my MA reads10 ft of altitude. If I stay level and now fly out over the ravine my altitude read out continues to read 10ft although the bottom of the ravine is now way below the drone, lets say 100 ft.. I have always assumed the drone was reading pressure altitude. Am I all wet?

This was my understanding, starting point is zero. No matter where you are.

Though now with UK law if you fly out over a drop/ravine/cliff and that is over 120m you're breaking the law. So the altitude reading can lull you into a false sense of height.
Though with my Air if I fly below starting height then a minis height is displayed.