Real agl ?

[Bbarr]

I’m new so tell me if I am stupid. So the altitude in the app is the agl from where I took off ? Not very useful. No way to know the agl of the AC ?

 

[RonW]

The app shows AGL above where take off point is, not above sea level.
In other words, if your take off point is 100 ft above sea level, then if you take the drone up 100ft, the app will show 100ft, not 200ft. Max height legally is usually 400ft above take off point.
Hope this clears it up for you.

 

[RonW]

To know height above sea level, you would need to consult Google Earth perhaps, and see what height your take off point is. Then add this to screen reading.

 

[Bernie707]

Bbarr, you’re exactly right, it’s the altitude above where you take off. This means if take off ftom a cliff and fly out a ways and descend you may get a negative altitude reading. Hence, you’re not stupid!

 

[bumper]

RonW, I respectfully disagree on the method for determining drone legal altitude. That altitude, typically 400' in the USA in non-controlled airspace, is measured vertically from the ground directly below the drone, or the the drone's AGL (Above Ground Level). When flying in hilly or mountainous terrain, legal altitude has little to do with the elevation of the takeoff point. Current drone AGL is not currently displayed on the controller. The drone would have to have a topo map database or a radar altimeter of some sort to provide that info.

MSL has little bearing for most drone flight, but it does when flying aircraft of course. The floor of Class A airspace is measured from Mean Seal Level and is 18,000. Above 18K one must normally* be equipped and licensed for IFR (instrument flight rules) and have a clearance from Air Traffic Control.

*At Minden NV we can sometimes get a variance, or Wave Window, for glider flight above 18K. I've been to 28K in my glider - it was cold. (picture of my glider at about 12K) - not taken with a drone! called a Wave

 

[Bbarr]

Thank you
Thats what I thought. Flew in flight

RonW, I respectfully disagree on the method for determining drone legal altitude. That altitude, typically 400' in the USA in non-controlled airspace, is measured vertically from the ground directly below the drone, or the the drone's AGL (Above Ground Level). When flying in hilly or mountainous terrain, legal altitude has little to do with the elevation of the takeoff point. Current drone AGL is not currently displayed on the controller. The drone would have to have a topo map database or a radar altimeter of some sort to provide that info.

MSL has little bearing for most drone flight, but it does when flying aircraft of course. The floor of Class A airspace is measured from Mean Seal Level and is 18,000. Above 18K one must normally* be equipped and licensed for IFR (instrument flight rules) and have a clearance from Air Traffic Control.

*At Minden NV we can sometimes get a variance, or Wave Window, for glider flight above 18K. I've been to 28K in my glider - it was cold. (picture of my glider at about 12K) - not taken with a drone! View attachment 92271called a Wave

 

[Bbarr]

Wow must of had oxygen...

 

[bumper]

Wow must of had oxygen...

Yes . . . I use O2 above 10K (5K at night) and a pulse oxymeter on my finger to make sure I didn't go stupid on that flight.

 

[RonW]

Bumper, read you comments, no offence taken. Maybe I didn't explain correctly - what I meant was that usually the max legal height is 400ft directly below drone to ground. I am aware that as the drone moves, the actual height relative to take off point may vary according to actual ground surface level, if that makes sense.
In the UK, the max height is 400ft vertically above ground level.
I stand corrected in that the display only reads height above take off point.
Again, sorry for any confusion.

 

[TDZHDTV]

 

[BigAl07]

View attachment 92316

It's important to note that graphic is NOT for the US/FAA regulations. It's very similar to US/FAA but all measurements are assuming a straight line between aircraft and ground.

 

[sar104]

View attachment 92316

But just to clarify - that's the UK CAA interpretation, not the FAA interpretation, which is true AGL.

 

[The Editor]

But just to clarify - that's the UK CAA interpretation, not the FAA interpretation, which is true AGL.

View attachment 92319

That’s an old graphic representation which has subsequently been removed to avoid the very confusion which has sparked from posting it.
@TDZHDTV - this is no longer used by the CAA to promote the agl requirements under ‘The Drone Code’

 

[DanMan32]

Bumper, read you comments, no offence taken. Maybe I didn't explain correctly - what I meant was that usually the max legal height is 400ft directly below drone to ground. I am aware that as the drone moves, the actual height relative to take off point may vary according to actual ground surface level, if that makes sense.
In the UK, the max height is 400ft vertically above ground level.
I stand corrected in that the display only reads height above take off point.
Again, sorry for any confusion.

But you did initially say legal limit is based from takeoff point.

 

[sar104]

That’s an old graphic representation which has subsequently been removed to avoid the very confusion which has sparked from posting it.
@TDZHDTV - this is no longer used by the CAA to promote the agl requirements under ‘The Drone Code’

So the CAA interpretation is now the same as the FAA's?

 

[Airborne_Aircrew]

There are two measures of altitude, QFE and QNH...

QFE is the altitude above "Field Elevation" and QNH is altitude above "Nautical Height"...

In normal aviation they both rely upon atmospheric pressure but you'll notice that you don't get a chance to enter the current pressure for the QFE or QNH... Your drone simply knows where it is in altitude as it takes off and works from there which is, effectively, QFE or where it took off from.

Neither one of these will give you your AGL, (Above Ground Level), because the ground changes height/atltitude but the pressure can remain the same... It'll be a while before a drone can give you true AGL data because it needs a Radar Altimeter that will cost a lot in weight and performance...

 

[sirbadger]

So the CAA interpretation is now the same as the FAA's?

This is what it currently says:

 

[sar104]

This is what it currently says:

View attachment 92341

Well there's a nice contradictory message. "Your drone or aircraft must never be more than 400 ft from the surface of the earth" is not the same as "never fly more than 400 ft above the surface", by which they clearly do mean AGL.

 

[The Editor]

So the CAA interpretation is now the same as the FAA's?

Yup

 

[Meta4]

Well there's a nice contradictory message. "Your drone or aircraft must never be more than 400 ft from the surface of the earth" is not the same as "never fly more than 400 ft above the surface", by which they clearly do mean AGL.

Without having an inspector up there on a long ladder with a long measuring tape, no-one is likely to ever be able to tell the difference anyway.