Hovering question....... please dont laugh

[Meta4]

Similar kind of question if I may... if I take off and hover at say 50ft.. and then fly over a quarry where the quarry floor is 400ft below... what happens to the drone? I have a Mavic Air. Does the height of the drone then become 450ft.. and now flying higher than permitted?!

What happens is the same as what would happen if a plane took off from the top of a high cliff and flew over the edge.

 

[Meta4]

How does it “know” what it’s height is when it takes off? GPS?
Why doesn’t it update it’s altitude when the terrain changes?

Its height at startup is always zero because that's how it is programmed to work
Your drone uses a barometric sensor to calculate altitude by measuring changes in air pressure - not GPS.
It doesn't update because it doesn't have any sensors to tell what's below (past 10 metres). just like most light aircraft.
It updates when there's a change in air pressure indicating a change in altitude relative to the launch point.
.

Anyone actually have real life experience flying off a cliff?

I'm pretty sure that someone, somewhere must have launched from a high point and flown below it.

 

[Starz]

If you take off from “x”, and you fly over a cliff and drop below point of “x”, your altitude will read a negative number.

 

[knewt]

If you take off from “x”, and you fly over a cliff and drop below point of “x”, your altitude will read a negative number.

Correct, launched from the top of the cliff part way through this. Launch height is zero, descend down the cliff and you’ll get a minus reading - see screenshot below.

 

[StevieJ]

Its height at startup is always zero because that's how it is programmed to work
Your drone uses a barometric sensor to calculate altitude by measuring changes in air pressure - not GPS.
It doesn't update because it doesn't have any sensors to tell what's below (past 10 metres). just like most light aircraft.
It updates when there's a change in air pressure indicating a change in altitude relative to the launch point.
.
I'm pretty sure that someone, somewhere must have launched from a high point and flown below it.

Ok... many thanks for the many answers surrounding this. If someone from the authorities was standing at the base of the quarry and the quarry floor to the top was 400ft and the drone was flying 50ft higher... this is still 450ft up in the air... so where do we stand with how high we're allowed to fly, given common sense and wind speed/ direction allows us to safely fly? Who would be in the right?
In today's news... man stands on top of a bridge and flies his drone. Yes I get he was daft in his actions... but was he just trying to get a higher flight legally due to our restrictions (although he missed the point a bit...)
Hope this makes sense....
Here's another scenario.... if I took off from the top of Catbells and was able to fly over Keswick.... my height would still be 400ft or under from launch height... but in reality...
I know common sense plays a part and all that but would some drone pilots be tempted to push boundaries this way... and more importantly, could they get away with it if they launch from a higher vantage point?

 

[Meta4]

Ok... many thanks for the many answers surrounding this. If someone from the authorities was standing at the base of the quarry and the quarry floor to the top was 400ft and the drone was flying 50ft higher... this is still 450ft up in the air... so where do we stand with how high we're allowed to fly, given common sense and wind speed/ direction allows us to safely fly? Who would be in the right?

You have to apply a little common sense, just as the hypothetical man from the authorities would.
The regulations are concise and don't go into voluminous detail about every convoluted exception.
There won't be a man from the CAA on a very tall ladder with a long tape measure to check your height at the quarry.
There also won't be airplanes flying within 50 feet of the cliff edge.

In today's news... man stands on top of a bridge and flies his drone. Yes I get he was daft in his actions... but was he just trying to get a higher flight legally due to our restrictions (although he missed the point a bit...)

If your bridge climber was hypothetically flying a drone, his location wouldn't make any difference.
The regulations are about where the drone is relative to the ground below it - not relative to the launch point.

Here's another scenario.... if I took off from the top of Catbells and was able to fly over Keswick.... my height would still be 400ft or under from launch height... but in reality...
I know common sense plays a part and all that but would some drone pilots be tempted to push boundaries this way... and more importantly, could they get away with it if they launch from a higher vantage point?

Same as above.
There are no regulations about your height above your launch point because it is irrelevant.
Perhaps this highly detailed artwork will illustrate why this is:

 

[DanMan32]

I'm just imagining an official using a really long tape measure and checking on us. Makes me laugh.
I want one of those tape measures. Mine collapses after 10' vertical.

 

[DanMan32]

Actually, if you go far enough out from the cliff, like 400ft or more, you could be in violation.
The practical problem would likely be more with helicopters than fixed wing. They seem to think they own the airspace and they can physically go just about anywhere, just as we can.

 

[Flycaster]

Watch youtube vid after vid on boat launches, AND especially the "landings"......
You'll soon forget about it......

 

[Snowstorm]

This seems to be terrible idea. Most cruise ship move pretty fast, like close to 40kmph, meaning just standing still with the deck is moving at 2/3 max flying speed of the Mavic. Landing at that speed would be difficult at best, add a bit of headwind and it would be impossible to even approach the ship.

Also, a cruise ship is about as bad as it gets for magnetic interference. Most of the structure is steel. It may just screw with the compass and cause a fly away intake off if left on GPS mode. Better hope you have configured the ATTi mode.

Lastly, almost all cruise line prohibit this activity. At sea, the captain’s demands is the law of the land (ship). Don’t want your bird or you to be confined to the brig.

 

[MArco-1]

I’m sitting on the fantail of a cruiseship which is underway....... aprox 20mph
I launch and hover my drone at ....... say 50 feet.
Will the drone be left hovering in place as the cruiseship moves away OR will it stay in place ......... hovering over me and the fantail

As others already mentioned, ask the cruise line for permission.. But to be honest, I launched and landed on a ship (during diving), and it is already difficult to land in my hand even if the ship is anchored, just moving a little bit... Overall a bad idea. At 20 or even 5 mph, you would be struggling controlling one handed and landing in your palm. Landing on a surface that is moving at 5 mph or 20 mph is just crazy and dangerous.

 

[bartjes]

A cruise ship is no polyester sailing boat but made of slot of steel that can interfere with your drone's compass and other sensors. A ship that size will still move pretty fast having a lot of wind up front making a drone launch treacherous. Landing via hand catch could be preferred. I was on such a boat and just left the drone in the cabin, not worth the risk.
If you're still a place where flying a drone in the harbour is allowed, why not do that ?

 

[Don Renaud]

Why not get a buddy with a pick up truck to try this out
You could try it at different speeds.
I would like to know the results

 

[ViperPilot]

Are you sure the Mavic w0uld even take off?? I'm thinking the algorithms for flight control would sense position movement based on the GPS info and not allow take off!

 

[Epp1983]

One more thing... whatever you do (theoreticaly) in this scenario, DO NOT PRIME THE MOTORS!
Doing so would cause the drone to auto-takeoff and if one wouldn't be expecting this, some injury could ocur.
Launching from the "Scroll to launch" option would be advised.

 

[pacsi]

OK, now I'm curious about the opposite end of the ship. Since the drone will stay stationery based on GPS, what will happen if you take off from the front of the ship? I assume the drone will stay still, but will the sensors do anything to try to prevent the superstructure of the ship from running into it?

I have experienced this situation myself. The boat was a 20 meters cruising boat and sailing no faster than 12 kts. The tallest part of the boat was only 6 meters over the deck where I was. I launched my Mavic Pro from the bow of the boat and suddenly she was flying to me (@ 12 kts, I guess), I avoided and collided with the cockpit. Fortunately, the drone flipped after the collision and ended up capsized on the deck. Only two props broken.

I changed the damaged propellers, I went to the stern of the boat to try it again. This time I position myself in a safe place, the Mavic took off and remained hovering, though the feeling was like the Mavic was flying away at high speed. I have to say that the Mavic was hovering in the place where she took off and was over the boat no more than two seconds.

After testing some Active Track modes was time to land. Forget about hand catch: it's too dangerous for your friends finger; not yours because you'll be very busy with the remote. At the end, I landed by crashing the drone over some mattresses I distributed on the deck.

The conclusion is, as WithTheBirds says, the Mavic doesn't know she was launched from a moving vessel and she was happily hover in position, but I was not. To land you have to fly at the speed of the boat plus the wind you have in that moment, which is not an easy manoeuvre. It was an exciting experience but too dangerous for the people around and with a high risk of end up with the drone in the bottom of the sea.

 

[Prmath]

Why not get a buddy with a pick up truck to try this out
You could try it at different speeds.
I would like to know the results

Our buddy Ken Heron already did. (in a big Boxtruck)..... Youtube clip. Very interesting

 

[BangkokFlyBoy]

I’m sitting on the fantail of a cruiseship which is underway....... aprox 20mph
I launch and hover my drone at ....... say 50 feet.
Will the drone be left hovering in place as the cruiseship moves away OR will it stay in place ......... hovering over me and the fantail

As most guys have said or inferred, this is a really BAD idea.

I did this once on what I thought was on a super slow ferry which turned out to be quite fast. Also there's the wind component to add to it and lastly, I was a newbie so panic (forgetting to switch of obstacle avoidance) compounded my situation.

I accidentally (And luckily) crashed my drone on the boat after fighting with it until it had 3% battery left!

Never doing that again even from a stationery boat. Not worth what these drones cost.

 

[BanditsRoost]

Why not get a buddy with a pick up truck to try this out
You could try it at different speeds.
I would like to know the results

I have landed (not launched) my MP on the bed of a truck and also through the open hatchback of a Honda CRV. Niether were hand caught and i was riding in a seperate vehicle. I've also launched and landed my P3SE from a moving 26' pontoon boat. The pontoon boat went fairly easy. If you try the moving vehicle route, I firmly believe these things "have" to happen in order to succed. First you must be prepared to make repairs. Next you must turn off all avoidance features. Then you must fly atti mode and lastly it ain't for the faint of heart. All repairs were due to trying it in GPS mode. I quickly grew out of that phase and now enjoy a much more relaxed flying method. To the original question....if you don't want me to laugh, you shouldn't ask humorous questions. ;-)

 

[Meta4]

Then you must fly atti mode and lastly it ain't for the faint of heart. All repairs were due to trying it in GPS mode.

Can you explain this?
I'm having trouble trying to imagine how that helps.