How high

[Peter mavic air]

May seem a silly question but...
If we are only allowed to fly 120 mtrs high,, is this above ground or above see level ?

 

[fmiroslav]

Above ground even if it’s below sea level[emoji26]

 

[DanMan32]

If it was based on sea level, a lot of us wouldn't have a place to fly.

 

[calmar81]

I live on about 430 meters... needed a huge excavator for flying, if it was above sea level

 

[FoxhallGH]

May seem a silly question but...
If we are only allowed to fly 120 mtrs high,, is this above ground or above see level ?

Hi @Peter mavic air - welcome to the Forum. You have not told us what country you are flying in, but here in the UK, you can think of it like this:

 

[Montana John]

Hi @Peter mavic air - welcome to the Forum. You have not told us what country you are flying in, but here in the UK, you can think of it like this:
View attachment 57406

In the diagram why is the height above the slope of the hill not measured vertically? Isn't a vertical measure required for AGL? What would AGL look like if the hillside were very steep, say 80 degrees?

 

[FoxhallGH]

What the diagram is telling me, is that you have an allowance for a maximum of 400ft (120 m) from the surface of the earth, over the range of the surface angles that you will see ... This means that if you fly out over e.g. a 500 ft cliff face, you can go out 400 ft from it, before you have to drop 100 ft in height (to be 400' above the surface at the base of the cliff). I've heard this talked about in terms like ... "Imagine the world was wrapped up in a 400 ft thick blanket That blanket represents the airspace that Drones are allowed to fly in."
It could catch on - but if we needed a scientific term for the first 120 metres of atmosphere, we could call it the "Dronosphere" ...

 

[Montana John]

And isn't the blanket metaphor erroneous? Do we not always want a vertical measurement from any given point on the planet. Lateral measure is not altitude, right?

 

[calmar81]

The new UAV legislation in our country always speaks of distances upwards and sideways from restricted areas (highways, power generation, hospitals, correctional facilities, etc.).

That's why it would make sense in such a "blanket" model, of course, when it comes to height specifications.

Let’s say I fly up a cliff with a complete vertical wall, it would make sense (also for lawmakers who want to ensure safety) that I‘m allowed to stay away sideways for a safe ascent / descent.

 

[FoxhallGH]

And isn't the blanket metaphor erroneous? Do we not always want a vertical measurement from any given point on the planet. Lateral measure is not altitude, right?

Correct - Lateral measure is not altitude ... Just like the height figures on your RC controller & Go 4 are not altitude either.
The blanket analogy is not really erroneous, because instead of thinking vertical, you need to be thinking about 'clearance' from ground and obstacles. In essence, the CAA reg's for light aircraft are trying to keep them clear of the ground and obstacles by a distance of 500 ft. The CAA are then allowing us clearance to fly our drones from the surface of the ground - or the obstacle - up to a distance of 400 ft - which should maintain a 100 ft 'separation' (not height-difference), between drones and light aircraft.
If you take your 'vertical measurement' literally, then you just would not be able [permitted] to fly out over the void from that 500 ft cliff face.

 

[FoxhallGH]

The new UAV legislation in our country always speaks of distances upwards and sideways from restricted areas (highways, power generation, hospitals, correctional facilities, etc.).

That's why it would make sense in such a "blanket" model, of course, when it comes to height specifications.

Let’s say I fly up a cliff with a complete vertical wall, it would make sense (also for lawmakers who want to ensure safety) that I‘m allowed to stay away sideways for a safe ascent / descent.

In the UK - we have a 'Dome-like' approach ... We are asked to keep 50 metres separation from buildings or people - and that's illustrated as a dome. To show why that's important, if I were to hover my Mavic 50 metres from a person, and 50 metres above launch zero, then (according to rules of trigonometry), the actual distance between the drone and the person, would be 70 metres. We are also asked to keep 150 metres separation from built up areas and/or crowds - and the only reason this doesn't work the same as a 'dome' is that we can't fly higher than 120 metres (400 ft) and therefore can't over-fly.
In regard to the vertical wall - yes - we should be able to fly from zero to 400 ft out from the vertical surface (be careful at the zero end tho').

 

[cyeung]

In United States Class G (uncontrolled) airspace, it is 400 ft. There are a few caveats:
1. For commercial operators, if you are within 400 ft. of a structure, you get the height of that structure in addition to the 400 ft.
2. For controlled airspace, you need to visit here: UAS Facility Maps for the specific limit. This limit, unlike the above, is hard and cannot be added to the height of any structure.

 

[FoxhallGH]

In United States Class G (uncontrolled) airspace, it is 400 ft. There are a few caveats:
1. For commercial operators, if you are within 400 ft. of a structure, you get the height of that structure in addition to the 400 ft.
2. For controlled airspace, you need to visit here: UAS Facility Maps for the specific limit. This limit, unlike the above, is hard and cannot be added to the height of any structure.

Thanks @cyeung ... What's the rules in regard to horizontal separation though ... e.g. if you come up against that 400 ft wall, and you want to go up and over it, are you allowed to do that within 400 ft horizontal of that wall??

 

[cyeung]

Thanks @cyeung ... What's the rules in regard to horizontal separation though ... e.g. if you come up against that 400 ft wall, and you want to go up and over it, are you allowed to do that within 400 ft horizontal of that wall??

From my understanding, yes, you can go up to 800 ft. above ground to scale the wall. To emphasize, that privilege applies only to uncontrolled airspace.

 

[FoxhallGH]

From my understanding, yes, you can go up to 800 ft. above ground to scale the wall. To emphasize, that privilege applies only to uncontrolled airspace.

Sorry - not making myself clear ... If for example, I was [in the USA] wanting to check out a communications tower that was 400 ft tall - OK - I can ascend to 400 ft above the top of that (i.e. to 800 ft above take-off), but how far away from the tower can I come horizontally, before I'm once again bound by the 400 ft rule and have to drop down again??

Or to put that another way - is there a cylinder of airspace 800 ft tall and 800 ft diameter around that communications mast I'm allowed to fly inside of??

 

[cyeung]

Sorry - not making myself clear ... If for example, I was [in the USA] wanting to check out a communications tower that was 400 ft tall - OK - I can ascend to 400 ft above the top of that (i.e. to 800 ft above take-off), but how far away from the tower can I come horizontally, before I'm once again bound by the 400 ft rule and have to drop down again??

That would be 400 ft. horizontal, so imagine a 800 ft. tall cylinder of 400 ft. radius.

 

[FoxhallGH]

That would be 400 ft. horizontal, so imagine a 800 ft. tall cylinder of 400 ft. radius.

Or even 800 ft diameter ... got it - Thanks for that @cyeung

 

[Peter mavic air]

Hi @Peter mavic air - welcome to the Forum. You have not told us what country you are flying in, but here in the UK, you can think of it like this:
View attachment 57406

I am from south Australia

 

[FoxhallGH]

I am from south Australia

Hi Peter - well - after all that ... I've told you what the reg's are here in the UK, but I'm not sure if they are interpreted the same in Australia?

 

[calmar81]

Here’s some information to be found: Flying drones or model aircraft recreationally