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400' AGL

unless we are suddenly going to find patrols of rangers ,law enforcement,or the CAA ,FAA,going out with specialised equipment to determine the height of our UAVs during a flight then all we can do is use some common sense and do our best to conform to the 400ft rule, not an issue,if the area you are flying in is relatively flat, a somewhat different matter in mountainous terrain where i fly in Wales i probably inadvertantly fly above 400ft AGL without even realising it at the time, because of the terrain i am flying in,its all a matter of perspective its much easier to determine your height from your home point if you keep in VLOS which for me is around 1,200ft with my old eyes
 
I always have understood that your height above AGL is always above take off point as recorded by the DJI app and Drone log.
 
Let's say he takes off from the top of the hill and heads to the right in this illustration. How does he determine his exact height while flying over the "valley"?
There is no way of knowing the exact height in the situation you mention since the height the drone will be reporting is relative to the take-off point, a radio altimeter would help but there is none.
 
The hight is from the controller, there is no way of you knowing what hight you are from a surface which may be at right angles from you.
 
The hight is from the controller, there is no way of you knowing what hight you are from a surface which may be at right angles from you.
If you’re standing on the top of a three story building and your ac is below you at ground level, where is your altitude recorded from?
Think about it.
 
The hight is from the controller, there is no way of you knowing what hight you are from a surface which may be at right angles from you.
Nope, it’s from the surface where the drone takes off.
You should have a topo map or aviation map and calculate your AGL height from the reading on your drone controller and that map... of course you don’t want to make it close, and a good argument for VLOS.
 
If you’re standing on the top of a three story building and your ac is below you at ground level, where is your altitude recorded from?
Think about it.

Your altitude is always recorded from your takeoff point. If you take off from the third story and fly down to the ground level, your remote and display will show negative altitude.
 
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Your altitude is always recorded from your takeoff point. If you take off from the third story and fly down to the ground level, your remote and display will show negative altitude.
That’s exactly what I was attempting to pass on to lets fly in post number 45.
Some people struggle a bit with simple math, which is what AGL is based on.
 
The key to all of this is the term”AGL”
If that is not something that can be understood by the person with the rc in their hand, they should remove it from their hands and find a different hobby.

Hmmm...I really hate that statement. If I told you to get another hobby based on anything arbitrary would you like it. So, if I fly from the side of a mountain horizontally ~1/4 mile and vertically ~ -1/4 mile what good does AGL do me. AGL doesn't tell me that I'm still 1000 ft. above the valley floor and now flying illegally. I have no idea what my drones altitude is unless I take @Thomas B recommendation to carry topographical charts with me. But wait, I have to know exactly where I am and the drone is to use that map. The drone doesn't have an altimeter in it so the fact is you can't tell how high , AGL, you are flying anywhere but directly above you. Everything else is your best GUESS!
 
Hmmm...I really hate that statement. If I told you to get another hobby based on anything arbitrary would you like it. So, if I fly from the side of a mountain horizontally ~1/4 mile and vertically ~ -1/4 mile what good does AGL do me. AGL doesn't tell me that I'm still 1000 ft. above the valley floor and now flying illegally. I have no idea what my drones altitude is unless I take @Thomas B recommendation to carry topographical charts with me. But wait, I have to know exactly where I am and the drone is to use that map. The drone doesn't have an altimeter in it so the fact is you can't tell how high , AGL, you are flying anywhere but directly above you. Everything else is your best GUESS!

So are you complaining that the technology is inadequate to keep you legal, or are you complaining about the requirement to remain at or below 400 ft AGL? Remember that you are supposed to keep the aircraft in sight, and so presumably you would also have some idea of the topography within that area. That would be part of the required situational awareness to be flying at all. If the ground drops hundreds or thousands of feet off the side of a mountain, then don't just fly 1/4 mile out in that direction without first planning the flight path.
 
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Hmmm...I really hate that statement. If I told you to get another hobby based on anything arbitrary would you like it. So, if I fly from the side of a mountain horizontally ~1/4 mile and vertically ~ -1/4 mile what good does AGL do me. AGL doesn't tell me that I'm still 1000 ft. above the valley floor and now flying illegally. I have no idea what my drones altitude is unless I take @Thomas B recommendation to carry topographical charts with me. But wait, I have to know exactly where I am and the drone is to use that map. The drone doesn't have an altimeter in it so the fact is you can't tell how high , AGL, you are flying anywhere but directly above you. Everything else is your best GUESS!
Ok.
I didn’t “told” anyone in particular.
It’s possible that the last twelve words in post number twenty may be
applicable to more pilots than I originally thought.
 
I always have understood that your height above AGL is always above take off point as recorded by the DJI app and Drone log.
That is only true if you are flying where the earth is pancake-flat.
But there are places where the earth is not flat.
The height shown in your app is not your height AGL.
 
So are you complaining that the technology is inadequate to keep you legal, or are you complaining about the requirement to remain at or below 400 ft AGL? Remember that you are supposed to keep the aircraft in sight, and so presumably you would also have some idea of the topography within that area. That would be part of the required situational awareness to be flying at all. If the ground drops hundreds or thousands of feet off the side of a mountain, then don't just fly 1/4 mile out in that direction without first planning the flight path.


Actually neither one. I'm complaining about @Starz saying that someone should get another hobby over something that has nothing to do with the altitude of the drone after it leaves the homepoint. I've only had mine at 400 one time just to see what the drone looked like at that altitude. But, if I had flown it straight from my house over the water it would actually be over 400' AGL but my app would have told me that I was at 400' and I'm at one of the flattest places you will find, the coast. I agree that situational awareness is definitely needed but I was trying to just state that I had gone out 1/4 mile and down 1/4 mile, not in any special way. But the awareness of topography does not mean that I can look at a small drone at 1000 ft away and tell what its altitude is whether it is above me or below me with differing terrain. While having an altimeter in the drone would be great, especially in places with differing terrain, the fact is that there is not one and the only AGL any of us sees on our remotes is relative and means practically nothing unless you fly over completely flat land. Can you tell me that if you fly down the side of a mountain to the valley floor that you can tell me whether you are below or above 400' at a distance of any consequence. I say do your best to follow these limits but that you cannot always tell when they have been broken without an altimeter in the drone and that I will keep my hobby no matter who thinks I or others should give it up over an arbitrary number, AGL, that has nothing to do with the altitude of the drone. It is just a number that might help you stay legal.
 
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You have to know the relative elevations from a map.. piloting skill.
I have the same concern you express when I launch from the top of the Mogollon Rim.., it’s a 2000’ high 300 mile long cliff crossing north central AZ. When I take off the home point is on top and my relative (to home point) and absolute altitude is 4 ft. When I fly 25 feet south my absolute altitude is about 2004’ as I fly out beyond the edge of the Rim.
You can use the negative number registered by your drone when you fly to a point below home point along with either flight or topo maps to compute altitude from the ground below.
Sorry to change subject but dam. That just sounds awesome to fly. Nice area. Lol
 
What makes it worse is each drone has it own height. Lol. I take off phantom 3 standard is different t to the phantom 4 to the spark to the Mavic and to other drones I have the same spot. Lol. Good news is no one will get the ruler /tape measure out to make sure. Lol. Not saying go break the rules but do you best to stay within limits.
 
What makes it worse is each drone has it own height. Lol. I take off phantom 3 standard is different t to the phantom 4 to the spark to the Mavic and to other drones I have the same spot. Lol. Good news is no one will get the ruler /tape measure out to make sure. Lol. Not saying go break the rules but do you best to stay within limits.
Could be the reason FAA set 100’ between drone max and airplane min altitudes... to allow for variation in equipment.
 
I just want to be clear with everyone. I fly Mountain terrain and I have a hard time with some jobs getting the data i need while remaining 400 AGL. Here is one example. If I am doing a wide shot of a property on the mountain side which is very steep. And from the total height of the mountain side is 1,300” with a 60 degree slope. Say your target is in the middle at when you fly 400 above the site to get the widest shot directly above your at 400. But if you go out away from the slope within 100’ you could technically be over 800’+ AGL (Directly below.). This is just an example. Now I posed this question to my local FISDO and the answer I got was as long as I stayed within 400‘ of the mountain side I would never have any problems. Now I know answers vary by who you talk to on any given day. So that what I do. My DJI data says I was flying at 1000+ ft for that flight but usually I never go over 300 AGL. Also, keep in mind that the top of the mountain is still 500‘ above my drone and any manned aircraft that would come into my flight area has way bigger problems then my drone. I do get the occasional helicopter doing power line or chemical spraying. So VLOS is paramount in any situation. Where 400 I have inquired about a flight height waiver but last time I checked the probability was low to get anything general for the area and is more per flight specific. Hopefully the FAA will get the rules defined a little better for situations like mine.
 
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