I know that FAA says 400' AGL. Most UAV's don't know what the surface is doing and the controller display shows height above "home" position where you launched from. If home isn't the lowest point during your flight, then the UAV will technically be more than 400' AGL assuming you went to the limit allowed. Of course some UAV's can do terrain following based on a loaded surface model, but not all. It would be cool if UAV's actually measured height AGL at all times.
Wondering about this, I emailed the FAA to get clarification, and here is direct quote; "The 400 ft AGL operating limitation is based on the altitude beneath the drone at any time".
To keep under the 400' AGL either fly way lower (to have a buffer) or launch from lowest point on the job (which is not usually what we want to do). Here in PNW where it isn't flatland usually the 400' AGL could be busted quite inadvertently when you have even a small valley, especially if you were on a hill so you can have VLOS.
Probably not going to get the FAA police chasing you, but something to keep in mind during planning.
PS, FAA was super responsive on answering e-mail, about seven hours, and that included some overnight hours as I emailed around 8pm PDT and received a response at 3am PDT. If you have a question it seems very good response times FYI.
SHG
It sounds like they expect you to fly using a radar altimeter.?ÿ Something similar to those described at https://integrated.ugcs.com/true-terrain-following .
Good luck.
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Well yes that would be best, then you could make sure to not bust the 400' AGL.
I suspect most either don't worry about it, or fly considerably under 400' above the launch point or project is such small area that relief doesn't come into play.
SHG
I can see where it would be a bid deal in mountainous terrain, maintaining 400' AGL would be impossible to do unless flying with a radar altimeter.?ÿ You are probably dead-on with your theory.?ÿ
Are you flying near a controlled airport where the FAA's radar could detect your UAV if you punched through the 400' ceiling??ÿ The only advise I can give, not being a UAV pilot, is to make every attempt to comply with the rules, be safe, and pray your vehicle and maned vehicles stay far apart from each other.?ÿ Good luck.?ÿ
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This is all theoretical, no specific project in mind, but do see where it could be an issue and why I asked the FAA. Bottom line is the pilot must never exceed 400" AGL under the UAV at any given moment and that is difficult to due if terrian isn't flat. I am a fairly new 107 pilot and just thinking about this for mision plans.
I am also thinking of this issue for our SAR unit where I am on the UAV team, almost always in the national forest for us and it would be very easy to violate the 400' AGL while on a mission. Obviously best to operate from a vantage point but that already puts the UAV potentially way above lower terrain surrounding you.
SHG
I almost always go to the highest point of the project and take off.?ÿ Saying that, I've never went to 400' AGL of my starting point.?ÿ I try to stay in the 150-200 range to maintain better data whether it's the P1 or L1.?ÿ Moreso the L1.?ÿ
I will have to look into this because I was under the understanding it was 400' AGL of your take-off point. I could be wrong.
We are flatlanders in the midwest compared to the PNW.?ÿ I may see 100-200 max of relief on a crazy site.
Based on the FAA exact response; "The 400 ft AGL operating limitation is based on the altitude beneath the drone at any time", I think it is obvious it is NOT 400' AGL at the launch point.
I agree, likely will NOT be 400' above the ground while mapping for accuracy reasons, BUT is definitely something to keep in mind even at 200' above take off point if the surrounding ground goes more than 200 feet lower, all of a sudden your UAV is more than 400' AGL at that particular point.
Maybe not for vertical mapping, but what about obliques of say of a cliff face at top of a canyon wall, around here that type of terrain is common and if standing on the rim, as soon as you go out over the edge you might be over 400' AGL. Not likely to be aircraft in that space to avoid, but it still breaks FAA rules.
This is something I have wondered for awhile, even during my course and testing and finally decided to ask the FAA.
SHG
For a specific project you can get a waiver from the FAA concerning the 400' limitation. ?????ÿ
@flga-2-2 true, but that seems impractical for every flight. I understand the 400' AGL and it is a good rule since other than take off landing cycles, manned aircraft generally are minimum of 500'AGL, keeps a vertical separation distance. A little harder to implement in undulating terrain, you definitely need to do more than just keep under 400' on your flight controller as that is likely to put you out of compliance. Just another thing to consider when planning a mission, where are you going to take off from and how high above the lowest point on project is that.
SHG
@pkm04558 yep, but not all UAV's are set up as nice as the Wingtra, definitely a nice platform and actually some thought into mapping by the engineers there.
SHG
400ft (120m) is pretty high. On a phantom rtk 20MP that??s something like 3-4cm gsd. You may find you almost never need to fly that high. I??m usually at 50-70m.?ÿ