Is 400 feet from sea level or from where u take off from ?

A DJI aircraft has no idea where sea level is, it has a barometer type altitude sensor, and measures from where you started the motors.

It is the relative altitude and the take-off point will be recorded as 0.

If you fly it downhill from where you took off, the altitude will read a negative number.

So in usa the height restriction is 400 feet. Faa don't make it clear . Im at 1800 feet above sea level where I live so i can fly at 2200 ft

Titanbot 4 Posted at 2017-10-12 18:23
So in usa the height restriction is 400 feet. Faa don't make it clear . Im at 1800 feet above sea level where I live so i can fly at 2200 ft

Yes, you can fly 400 feet above your starting point, but you must respect any other air traffic around you.

Cool, its the other air craft im worried about, dam eagles keep coming after it,

Titanbot 4 Posted at 2017-10-12 18:36
Cool, its the other air craft im worried about, dam eagles keep coming after it,

Remember that eagles can't fly straight up like you can and find it hard to fly straight down - set your height limit high so that you can always avoid them, they will learn not to bother after a while.

And don't change the colour of your Phantom to eagle prey colour!

Titanbot 4 Posted at 2017-10-12 18:36
Cool, its the other air craft im worried about, dam eagles keep coming after it,

Aloha Titan,

     There is also another factor that determines altitude in the USA.  Structures.  The FAA regulations allow Pt. 107 flight within 400 feet of structures.  Structures are towers, tall trees, bridges, buildings, mountains and hills, etc.  If you live near a mountain with an altitude over 1640 feet (500 meters), you can fly within 400 feet of the mountain all the way up to the max altitude of your Phantom, 1640 feet.  I live next to approximately 2000 foot cliffs (Pali) and do it all the time.



     Hope this helps!

Aloha and Drone On!

Geebax Posted at 2017-10-12 18:06
A DJI aircraft has no idea where sea level is, it has a barometer type altitude sensor, and measures from where you started the motors.

Hi Geebax

I know you have a lot of knowledge regarding those things, but somehow it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?
That it don't work very well is another thing, at 09.09.2017 my stats now claim that Top Altitude should be 1675.0 m, i am sure nothing in Denmark would make this possible at all ...

Not that i know of the US rules but i would suppose that the 400 limit would be relative to ground level and not take off level so actually one is supposed to descend as ground get lower if tex. taking off from a mountain, is that a wrong understanding i have here?
I think that if taking off from a very high point and raise to your 400 limit and take to all i can reach of distance you would be way to high or ?

If you're talking about FAA guidelines, the key acronym is "AGL."  AGL = Above Ground Level.  If you're flying recreationally, you should fly within 400' of the ground immediately below your AC regardless of whatever towers or buildings are around you.  If you're flying 107, you can add height relative to the buildings and towers around you.  

All good answers to what can be a confusing thing!

Nigel_ Posted at 2017-10-13 00:11
Remember that eagles can't fly straight up like you can and find it hard to fly straight down - set your height limit high so that you can always avoid them, they will learn not to bother after a while.

And don't change the colour of your Phantom to eagle prey colour!

Just the other day only 30 feet above river was just hovering and one came within a few feet , i stopped flying cause i didn't want to get him/her hurt

KedDK Posted at 2017-10-13 02:18
Hi Geebax

I know you have a lot of knowledge regarding those things, but somehow it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?

'but somehow it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?'

I have no idea how DJI calculate 'Top Level', it always seems to be wrong anyway, so I ignore it. But the aircraft has no idea where 'sea level' is. As I stated earlier, it uses a barometric pressure sensor to measure its altitude, just like a real aircraft does, so it only knows its altitude above the take-off point. This is because it resets the altitude to zero when you start the motors.

'Not that i know of the US rules but i would suppose that the 400 limit would be relative to ground level and not take off level so actually one is supposed to descend as ground get lower if tex. taking off from a mountain, is that a wrong understanding i have here?'

The 400 foot limit is relative to the ground you are flying over, and in certain circumstances, relative to a structure that rises above ground level.

'I think that if taking off from a very high point and raise to your 400 limit and take to all i can reach of distance you would be way to high or ?'

If, for example, you took off from a point 100 feet lower than the summit of a mountain, you can then fly upwards 500 feet so you are now 400 feet about the summit. That puts you at 400 feet AGL ( Above Ground Level).

Geebax Posted at 2017-10-13 16:20'Not that i know of the US rules but i would suppose that the 400 limit would be relative to ground level and not take off level so actually one is supposed to descend as ground get lower if tex. taking off from a mountain, is that a wrong understanding i have here?'

Gound level and take off level are considered the same, as ground level is assumed to be where you took off from.

Where in the world do you come up with this nonsense?  Please do not mislead the membership.  

OP - See my post above.

KedDK Posted at 2017-10-13 02:18
Hi Geebax

I know you have a lot of knowledge regarding those things, but somehow it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?

it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?

The Top Altitude shown does come from GPS altitude.  It's the altitude inmetres of the higherst point you've launched from.
GPS gives altitude data as well as position but the Phantom completely ignores this and only uses the barometer for all in-flight data.
In-flight, your Phantom only knows one height and that is Home = zero.

Mark The Droner Posted at 2017-10-13 17:04
Where in the world do you come up with this nonsense?  Please do not mislead the membership.  

OP - See my post above.

I have modified my post, it was not intended to confuse, and keep it civil, there is no need for rude posts.

Geebax Posted at 2017-10-13 16:20
'but somehow it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?'

I have no idea how DJI calculate 'Top Level', it always seems to be wrong anyway, so I ignore it. But the aircraft has no idea where 'sea level' is. As I stated earlier, it uses a barometric pressure sensor to measure its altitude, just like a real aircraft does, so it only knows its altitude above the take-off point. This is because it resets the altitude to zero when you start the motors.

Thank you for clearing out the rules, also thanks to Mark for specifying different licenses different limits.

Still confused about that "Top Level" thing and how wrong it can be as i always have plenty of Sats (11+) before even starting the motors. 1675m is some of a miss from an actual takeoff around 20m above sea.

Labroides Posted at 2017-10-13 17:25
it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?

The Top Altitude shown does come from GPS altitude.  It's the altitude inmetres of the higherst point you've launched from.

Thank you, yes i also think that the GPS signal is used for the Top Altitude thing and somehow happy it is not used for the general height measurement during flight as it seem to be way off sometimes.

Also i believe that the barometer get it wrong but only within some few meters, often my landing height is wrong and i suspect the heating of the craft during flight does influence the barometer readings due to change of pressure warm vs cold.

KedDK Posted at 2017-10-13 02:18
Hi Geebax

I know you have a lot of knowledge regarding those things, but somehow it must know something about sea level as the "Top Altitude" from Flight Stats seem to refer to this value?

Aloha Ked,

     Could you check if the "Top Altitude" 1675 measurement is actually in feet?  1640 feet is 500 meters.  If the reading is in feet, it would translate that the measurement is taken from 35 feet above sea level somehow.  The map software often has height above sea level included in any designated spot.  500 meters is the max altitude that the Phantom is computer-regulated to fly.  Please understand that this suggestion is a long-shot.

     In the USA, the 400 foot altitude limitation is a FAA regulation, not a physical limitation.  Before I set my max altitude to 500 meters (1640 feet), I used to fly up 100 feet and land on a "flats" and shut off the motors.  When the Phantom restarted, it would declare the flats as the home point and I would have another 400 feet to fly.  When I flew home from the flats, I would land at my original location and the altirude would read a negative 100 feet.

     Hope this helps!

Aloha and Drone On!

Cetacean Posted at 2017-10-13 20:51
Aloha Ked,

     Could you check if the "Top Altitude" 1675 measurement is actually in feet?  1640 feet is 500 meters.  If the reading is in feet, it would translate that the measurement is taken from 35 feet above sea level somehow.  The map software often has height above sea level included in any designated spot.  500 meters is the max altitude that the Phantom is computer-regulated to fly.  Please understand that this suggestion is a long-shot.

Hi

No it is not in feet, from my old thread here you can see i was confused of the 72.3m value.
at first i thought that top altitude was my max flight height but according mods it is displaying the "Take Off" altitude but i have done no takeoffs from that altitude and for sure also not from 1675m as it now claim i did on 9th of September.

I am convinced that it has to do with the GPS issues experienced among other after the 01.04.0602 June upgrade. Unstable GPS interpretation also would explain the unstable hoovering a lot of us has got.

KedDK Posted at 2017-10-13 21:28
Hi

No it is not in feet, from my old thread here you can see i was confused of the 72.3m value.

Aloha Ked,

     OK, well I guess I live on the lucky side of the world.  My sattelites provide steady and proper readings.  Maybe my humid (most of the time) emvironment keeps my barometer on its toes to.  Good luck.

Aloha and Drone On!

KedDK Posted at 2017-10-13 21:28
Hi

No it is not in feet, from my old thread here you can see i was confused of the 72.3m value.

'I am convinced that it has to do with the GPS issues experienced among other after the 01.04.0602 June upgrade. Unstable GPS interpretation also would explain the unstable hoovering a lot of us has got.'

Actually, hovering. Hoovering is used for cleaning carpets. No, the aircraft does not use GPS height for any of it's control operations, and that is primarily because of the extemely poor accuracy of GPS height measurements. Altitude is controlled in the main by the barometer, and also by the VPS system if it is within 10 Feet of the ground.

Geebax Posted at 2017-10-13 21:39
'I am convinced that it has to do with the GPS issues experienced among other after the 01.04.0602 June upgrade. Unstable GPS interpretation also would explain the unstable hoovering a lot of us has got.'

Actually, hovering. Hoovering is used for cleaning carpets. No, the aircraft does not use GPS height for any of it's control operations, and that is primarily because of the extemely poor accuracy of GPS height measurements. Altitude is controlled in the main by the barometer, and also by the VPS system if it is within 10 Feet of the ground.

Thanks for the correction, sorry that English is not my native language, hopefully it was better understood than hvis jeg havde skrevet mit indlæg på dansk. ;-)

KedDK Posted at 2017-10-13 21:56
Thanks for the correction, sorry that English is not my native language, hopefully it was better understood than hvis jeg havde skrevet mit indlæg på dansk. ;-)

Ok, it is a common error, although 'hoovering' might not have translated in Danish anyway

KedDK Posted at 2017-10-13 21:28
Hi

No it is not in feet, from my old thread here you can see i was confused of the 72.3m value.

as it now claim i did on 9th of September.
.... I am convinced that it has to do with the GPS issues experienced among other after the 01.04.0602 June upgrade. Unstable GPS interpretation also would explain the unstable hoovering a lot of us has got.

It's extremely unlikely that it has anything at all to do with a firmware update.
It's very uncommon but you can occasionally get a spurious GPS fix.  Perhaps that is the answer.
Since you have a date, it would be a simple matter to check the flight record for that flight and it might show something about the GPS sats during the flight.

KedDK Posted at 2017-10-13 21:56
Thanks for the correction, sorry that English is not my native language, hopefully it was better understood than hvis jeg havde skrevet mit indlæg på dansk. ;-)

Aloha Ked,

     As Labroides indicated, you could go into the flight records since you have a date and check your flight.  The Forum recently posted a new thread on reading the flight records;

https://forum.dji.com/thread-114810-1-1.html

Give it a look, maybe it can help you.  At least it can give you something to do when it rains and the wind is too strong - both of which are happening to me in Hawai'i right now!

Aloha and Drone On!

Titanbot 4 Posted at 2017-10-12 18:23
So in usa the height restriction is 400 feet. Faa don't make it clear . Im at 1800 feet above sea level where I live so i can fly at 2200 ft

There is no 400 feet height restriction in the USA for hobby drone pilots.

You can fly higher than that and many do.  If you are at 1800 feet already then you are clear to fly higher than that point.  

Re hobbyists, there is a 400' height restriction guideline per the FAA.   

https://www.faa.gov/uas/getting_started/fly_for_fun/

http://knowbeforeyoufly.org/for-recreational-users/

I don't know or hear of many UAS pilots who deliberately or routinely fly over 400' AGL - Taiwan excluded.  

But yes, technically, there is no law in the US that applies directly re the 400' AGL height restriction guideline.  The law applies when one flies high enough to endanger the national airspace system.  

Labroides Posted at 2017-10-14 00:23
as it now claim i did on 9th of September.
.... I am convinced that it has to do with the GPS issues experienced among other after the 01.04.0602 June upgrade. Unstable GPS interpretation also would explain the unstable hoovering a lot of us has got.

I hope OP has got answer for his question before this goes to far but ...

It is not that easy for me to check that record, it is not on my list anymore. To make it even more (not) funny it got worse after i tried to re-sync, some more got lost, seem to be my latest speed record and 5km/18 min. flight...
Both of those has been synced up to the DJI cloud, i think last sync was made on the 11-12th of September, very thrustverthy system ...

Edit: i can see from the sync log i synced on the 10th. but the record is not expected to disappear anyway.

Thx anyway, guess i just have to live with it or return this PoC if not they get the bugs fixed soon. :-(

Above the ground in which your drone is flying.