So can anyone tell me if my understanding for the FAA rule is correct: I am allowed to fly on a roof top (assume it's 800 feet high already) within 400 feet, right? But I'm not allowed to climb down(say, 100 feet) below the roof top since then the AGL would be like 700 feet from the ground.

Please educate. Thank you!

It's 400 AGL top of your roof is not the ground it's a roof 800ft above the ground, it's easy to work that out."

If you remain within 400' of the structure you can go 400' above it under part 107
https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=20516

As a hobbyist it's strickly 400' AGL
https://www.faa.gov/news/updates/?newsId=85264

As a hobbyist it is recommended you stay below 400' Above Ground Level, but there is no law / requirement. Just guidelines.

Alright I'll argue this I fly on the Iowa bottom right next to me is a 600 foot tall bluff so I want a better view I go to the top of the bluff and go 400 feet don't see a problem.

rydfree41 Posted at 2017-3-25 14:42
If you remain within 400' of the structure you can go 400' above it under part 107
https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=20516

Thank you for the reply. But I just thought of another thing.....I get that flying among structures is already bad practice. I won't do that then. But mountains are different from buildings, right? I can fly on top of a mountain(that mountain might be like 1000 feet high) since the "ground" would be the take-off point on the mountain

geofox784 Posted at 2017-3-25 15:09
As a hobbyist it is recommended you stay below 400' Above Ground Level, but there is no law / requirement. Just guidelines.

yeah....I know...sometimes I just don't want to do something they don't suggest and give them reasons to get me into trouble you know? Even though I don't think I have ever exceeded 200 feet

It's a guideline based on where in the airspace other traffic is. they set 400' as a guideline as normal airlines have to fly way above that, so you should never be in the path of any other commercial or domestic flights, thats not set in stone though and i myself have witnessed a helicopter flying well below the minimum that they should be flying.

You just have to use common sense and if you ever hear another aircraft, land asap.

I remember my parents setting guidelines . They quickly became law when broken

Don't mean to re-bump this but it was never really addressed. I had a similar issue today flying over a large "hill" near my place in the country side.
By the 400 foot argument, the skiers on that hill are in violation of FAA rules as they pose risk to airplanes.

Logically you need to be above the object height you are filming, but once that object is passed you can descend to a safe height.
Alternatively if I take off from a 400 foot hill and continue flight path to lower altitudes I will be 800 feet above the ground and app reading will still show only 400.

Linuxglobal Posted at 2018-6-21 06:37
Don't mean to re-bump this but it was never really addressed. I had a similar issue today flying over a large "hill" near my place in the country side.
By the 400 foot argument, the skiers on that hill are in violation of FAA rules as they pose risk to airplanes.

The rule/regulation is 400ft AGL(above ground level) not above sea level.    If you are on a mountain, and you are at 1000' altitude, your flight can go up to 1400' altitude because it is still only 400ft AGL.

There is also the FAA reg that states that you can go above 400ft AGL if you are within 400 ft of a structure.  which means that if you take off from the roof you can go up to 400 ft above the structure, but only as long as you are within 400ft distance.

So if you are flying 400 ft above buildings, then you are flying within the regulation.

In your example, If you fly from a hill that is 400 ft and you fly over the valley below, which puts your aircraft 800 ft above the ground, you are still within the rules because you are flying 400ft AGL from your take off spot.

I hope this clears it up for you

I am on 300 feet takeoff and fly to a hill over 600 feet above me. So I fly to maximum 1000 feet high from sea level and my flight record show maximum high is 700 feet. Did I break any rule? No, I just fly around 100 feet above the ground all the way. It’s different with fly the drone over 400 feet directly above your head.

Going up by following the terrain you can fly much higher than 400 feet. Just need to ensure the ground below you drone is less than 400 feet away.

3-D Posted at 2018-6-21 07:45
The rule/regulation is 400ft AGL(above ground level) not above sea level.    If you are on a mountain, and you are at 1000' altitude, your flight can go up to 1400' altitude because it is still only 400ft AGL.

There is also the FAA reg that states that you can go above 400ft AGL if you are within 400 ft of a structure.  which means that if you take off from the roof you can go up to 400 ft above the structure, but only as long as you are within 400ft distance.

If you fly from a hill that is 400 ft and you fly over the valley below, which puts your aircraft 800 ft above the ground, you are still within the rules because you are flying I400ft AGL from your take off spot.


The only thing I would disagree with you here is the rule is 400' AGL from you take off point whether a roof top or mountain extends out from your takeoff point only 400'. So if you take off from a hill that is 1000' elevation you can fly up to 1400' but the minute you fly more than 400' away in distance and the hillside slopes down you must lower your altitude to maintain the 400' rule. Pilots (mainly smaller AC) in mountainous areas often fly within valleys to escape winds, the 400' AGL / 400' Distance rule applies at all times during flight. One of the Part 107 questions.

QuadKid Posted at 2018-6-21 08:35
If you fly from a hill that is 400 ft and you fly over the valley below, which puts your aircraft 800 ft above the ground, you are still within the rules because you are flying I400ft AGL from your take off spot.

point taken.  Thank you

Important thing to remember whether to use ASL (above sea level) or AGL (above ground level). DJI aircraft do not have barometric pressure sensors to provide measurements that would indicate altitude in ASL. The only sensors are getting information from satellite and ground relay stations which only provide altitude measurements in AGL. In the US, you can fly commercially above 400 feet AGL as long as you are within 400 feet of a structure. But this does not include things like bluffs, cliffs, hills, etc. That being said, if you were to be at the bottom of a cliff, for example, and you flew 400 feet above the top of the cliff, you would not be in compliance for commercial flights, but that would unlikely be an issue with any authority. Rather, you would need to be more concerned with maintaining VLOS (visual line of site). At 400 feet plus the additional height of the cliff, you would unlikely be able to see your aircraft without the aid of binoculars. Hope this helps!

DJI Flight Ops Posted at 8-10 10:59
Important thing to remember whether to use ASL (above sea level) or AGL (above ground level). DJI aircraft do not have barometric pressure sensors to provide measurements that would indicate altitude in ASL. The only sensors are getting information from satellite and ground relay stations which only provide altitude measurements in AGL. In the US, you can fly commercially above 400 feet AGL as long as you are within 400 feet of a structure. But this does not include things like bluffs, cliffs, hills, etc. That being said, if you were to be at the bottom of a cliff, for example, and you flew 400 feet above the top of the cliff, you would not be in compliance for commercial flights, but that would unlikely be an issue with any authority. Rather, you would need to be more concerned with maintaining VLOS (visual line of site). At 400 feet plus the additional height of the cliff, you would unlikely be able to see your aircraft without the aid of binoculars. Hope this helps!

DJI aircraft do not have barometric pressure sensors to provide measurements that would indicate altitude in ASL.
Every DJI drone has a barometric sensor which is its primary altitude sensing device.
It gives height relative to home = zero.
The drone does use GPS for altitude.

Important thing to remember whether to use ASL (above sea level) or AGL (above ground level).

You will only confuse by mentioning sea level as it has no relevance in drone flying.