Question about 400ft AGL on mountainous terrain

[TnDronePilot]

Strange question. When it comes to AGL maximums in areas with mountains or large hills, I'm assuming the drone's zero foot measurement is from the launch point correct? I brought my MA2 out to my cabin which is a few miles outside the Great Smoky Mountains boundary. The cabin is few hundred feet above and about 1/4 away from the main drag of Pigeon Forge, TN. As I was flying around, I had a thought. If I hypothetically flew down to the street level and landed, would I now be restricted to 400ft from that AGL after re-launch or my original launch point at the cabin?

 

[Phantomrain.org]

Strange question. When it comes to AGL maximums in areas with mountains or large hills, I'm assuming the drone's zero foot measurement is from the launch point correct? I brought my MA2 out to my cabin which is a few miles outside the Great Smoky Mountains boundary. The cabin is few hundred feet above and about 1/4 away from the main drag of Pigeon Forge, TN. As I was flying around, I had a thought. If I hypothetically flew down to the street level and landed, would I now be restricted to 400ft from that AGL after re-launch or my original launch point at the cabin?

Yes its from your launch point unless you remote land , shut down the motors and restart with a new home point.

Phantomrain.org
Gear to fly your Mavic in the Rain and Land on Water.

 

[MA2 317]

No its from your launch point unless you remote land , shut down the motors and restart with a new home point.

Phantomrain.org
Gear to fly your Mavic in the Rain and Land on Water.

It would be labeled ALP (Above Launch Point) and not AGL (Above Ground Level).

When I launch from the lake side in the valley and follow the terrain up the hill to the top, I'm under 400 feet AGL at the top of the hill but may be 1000 feet above my launch point.

I know I can't launch and go straight up to a thousand feet and then go over to the top of the hill, but if I follow the ground and remain under 400 feet AGL, I'm compliant.

 

[Phantomrain.org]

MA2 317" data-source="post: 1176676" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

It would be labeled ALP (Above Launch Point) and not AGL (Above Ground Level).

When I launch from the lake side in the valley and follow the terrain up the hill to the top, I'm under 400 feet AGL at the top of the hill but may be 1000 feet above my launch point.

I know I can't launch and go straight up to a thousand feet and then go over to the top of the hill, but if I follow the ground and remain under 400 feet AGL, I'm compliant.

Edited , Thank you.

 

[THE CYBORG]

 

[dronerdave]

View attachment 120801

That image is more related to 107 flights. IIRC in the US it's 400' directly below the aircraft for recreational flying. So that middle line must be straight down as the other two.

 

[robwas]

It's an interesting question I too had, however when you factor in needing visual line of sight to be legal unless you have a really big drone or fantastic vision I find it hard to see my drone very far from my launch point, I'd say about 2000' is the limit for my eyesight unless it's at dusk and I can see the lights. I know people really get into what's technically legal but personally if I launch from a higher location and feel there's any chance my drone might be up where a plane could collide with it I wouldn't go there. Where I live most planes seem to be at least 1000' up (I live in a populated area) so I'd be hard pressed to get into their airspace. One thing I will say is how can you know if you're under 400' AGL when your software on the controller only tells you how high you are in relation to where you took off? I guess you could study a top map or even guess but I think getting this right to any degree of accuracy would be very difficult.

 

[DanMan32]

That image is more related to 107 flights. IIRC in the US it's 400' directly below the aircraft for recreational flying. So that middle line must be straight down as the other two.

The structure bubble isn't what Cyborg is showing. UK has to be within 400ft diagonally of a hill as well as directly down. We don't, it's only down.

 

[dronerdave]

The structure bubble isn't what Cyborg is showing. UK has to be within 400ft diagonally of a hill as well as directly down. We don't, it's only down.

Yep. the OP is in the US so that image doesn't apply to FAA rec rules. It doesn't matter where you take off or land at. The aircraft must stay at 400' AGL or less directly below the aircraft. I often fly up a steep grade on a mountain side. I can fly up the side of the mountain VLOS and climb up to distances well beyond 500 feet and maintain below 400' AGL the whole way. I usually can fly above the tree tops and know I'm in compliance. If it's a sheer vertical cliff taller that 400 feet, I can't go above that if directly below is further than 400'. I do think rec fliers should be able to similar to what they can in the UK but we can't.

 

[jeff4smith]

I often fly up a steep grade on a mountain side. I can fly up the side of the mountain VLOS and climb up to distances well beyond 500 feet and maintain below 400' AGL the whole way.

To accomplish this I assume you must increase the maximum altitude in the DJI app since it is measuring from the original take off point? I'm actually surprised the software doesn't calculate actual AGL rather than the altitude from the take off point, seems like this would not only be more useful information especially in areas with varying terrain but also in sync with how AGL is defined in FAA regulations.

 

[Rich QR]

I'm actually surprised the software doesn't calculate actual AGL rather than the altitude from the take off point, seems like this would not only be more useful information especially in areas with varying terrain but also in sync with how AGL is defined in FAA regulations.

It would be nice, wouldn't it?

But to compute height AGL, it would need either some form of radar altimeter, or a digital model of the earth with sufficient detail. Airliners often do it with a radar altimeter, but that's too big, heavy, expensive, and power-hungry for a drone.

A digital elevation model of the USA is available from the USGS, but it would be many hundreds of gigabytes (depending on resolution), and would of course be useless outside the USA.

Map - 3DEP File Size | U.S. Geological Survey

www.usgs.gov

 

[Hokyfan]

The FAA regulations is ALWAYS 400' AGL - not fro, where you launch, but from where the drone is currently located. The only exceptions to that are when you are within 400' of a structure, then you can fly 400' above the structure and when you are in restricted airspace where you need to stay below the max ceiling for that location.

 

[Rich QR]

The FAA regulations is ALWAYS 400' AGL - not fro, where you launch, but from where the drone is currently located. The only exceptions to that are when you are within 400' of a structure, then you can fly 400' above the structure ...

But only if you have your Part 107 license and are flying under Part 107 rules. Recreational flyers are always supposed to stay below 400' AGL.

 

[BigAl07]

The FAA regulations is ALWAYS 400' AGL - not fro, where you launch, but from where the drone is currently located. The only exceptions to that are when you are within 400' of a structure, then you can fly 400' above the structure and when you are in restricted airspace where you need to stay below the max ceiling for that location.

As stated, the "Structure Allowance" is only for Part 107 operations. Recreational operations do not need nor allow for being within 400' of a structure.

 

[Thomas B]

Here’s one 2 miles south of my home where I used the within 400’ rule. But since the peak of Santan Mountain is 2200’ I had to find a place, land and take off again to see over the summit. Alas the land is leased now an the lessee does not allow drones.., don’t know when or if this flight will be possible again... a bit long at about 6 min..,,

 

[dronerdave]

To accomplish this I assume you must increase the maximum altitude in the DJI app since it is measuring from the original take off point? I'm actually surprised the software doesn't calculate actual AGL rather than the altitude from the take off point, seems like this would not only be more useful information especially in areas with varying terrain but also in sync with how AGL is defined in FAA regulations.

In that terrain I rarely go past the max limit of 1600 feet, but yes I have set ceiling altitude in the app to 500m. I'd rather not go too far and prefer being able to see obstructions visually. I don't know my actual altitude directly below the quad but between looking at the video feed and the quad itself, I know I'm not above 400' directly below my Mavic Pro.