I’m sorry to delve into the 120m AGL debate again but I was thinking about a scenario last night as I was trying to get off to sleep.
I appreciate that we have to stay within 120m of the ground at all times but what would happen in the case of the attached graphic?
In theory, if you flew over the cliff (black arrow) would there be any restrictions besides a legal one?
Many thanks
Hi Barry, as far as I understand it you have to be 120m (400ft) from the closest point to earth which would be the cliff face not sea level.
Thanks Jason. Yes I was aware of the 400ft restriction, I was just wondering if there was a physical restriction, like the drone suddenly dropping to 120m once it had gone over the cliff for example.
surely if you have taken off from the edge of a cliff,the closest point of the earth is still where you have taken off from? i.e The closest point to the drone,vertically that is not horizontally
No, its the height from your take off point on you controller. Its quite possible for you to take off climb to 120m then fly out to sea for 600m as long as you take off height is not above 120m (which is restricted now on C0/UK0 drones). Although this would be illegal as you must not be more than 120m from the nearest point to earth.
I was thinking that as well! Does the drone measure it’s height from the controller or the ground?
Its measured from the controller, which is zero when you take off. So if you take off from the base of a cliff, and the cliff is 125m heigh you cannot fly over it, yet if you take off from the top of the cliff you can fly 120m above your take off point and also fly down to the base of the cliff. Which is why so many people are saying the forced 120m limit is wrong. Its a bit confusing but hope you get my point.
Many thanks for the explanation.
Soooo, if I can labour the point, am I right in thinking that (in my graphic) I could take off from the top of the cliff - fly out over the sea maintaining the same height (although it would be well above 120m) - then return to my take off point at the top of the cliff?
that would be my interpretation
that’s how I would see it as well but can you imagine flying somewhere like Beachy Head,you’ve got some great footage or photos of the lighthouse there and then you press RTH only for the drone to happily hover 100ft below the cliff edge until the battery gives out lol no wonder people get nervous about it!
OK lets say you took off from the very edge of the cliff,(please don’t), climb to 120m, then flew out to sea, you could only fly out 120m out then you would have to drop the drone to 120m from sea level, remember you must not be more than 120m away from the earths surface, so for the first 119m you would be 120m plus cliff height above the beach then the sea. but at 120m you would need to drop the drone to be 120 from the sea level. Wow harder to write than understand.
Ha ha ha you got that right, but I do get it. Thank you SO much for the great comments 
hopefully it would return back to its take-off point!
