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Going down a crater
242 9 2020-8-23
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mr.jipi_
lvl.2
Flight distance : 73248 ft
Canada
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There is a huge hole (like a crater) from an old mine. Is there anything I should know before trying to fly down that hole?  It’s at least 40 meters wide by 30 meters deep. I was wondering if having the drone going in the “minus” (like -8 meters) was a problem? I would stand on the edge of the crater with the controller facing the drone.
Thanks

2020-8-23
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Geebax
Captain
Australia
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Yes, you need to be prepared to fly the aircraft in full manual guidance mode (ATTI) as you will probably not see enough GPS satellites when the aircraft is down the hole.
2020-8-23
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gnirtS
Captain
Flight distance : 2993497 ft
United Kingdom
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Negative altitude is no problem but as above you may lose GPS or worse, get a weak or intermittent GPS means it bounces around all over the place.  Vision sensors may not work if the light isnt good either.
Id do the flight but using ATTI mode.
2020-8-23
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JJB*
Captain
Flight distance : 6621798 ft
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Netherlands
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Uh, if you fly into that hole, atti when your loose GPS or OPTI when there is still enough light.

Read the manual for this ; max height is limited to 5 or 30 meters. But this height is measured by the VPS sensor if enough light available ; 5 meter max from that point.
Worst case scenario ; not possible to fly drone UP again to fly out of this hole if VPS sensor is active and measure height (even if sensor measures a faulty height!)


cheers
JJB
2020-8-24
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mr.jipi_
lvl.2
Flight distance : 73248 ft
Canada
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Thank you for your help. Light shouldn't be a problem. It's a big hole and I can see the bottom without problem, but there is water.

On the Mavic 2 pro, ATTI mode I think must be enabled through the “debug mode”  using the Assistant App on a computer. This is something I haven’t done yet and I would need to train for that kind of flight.

If I enable this mode (let’s say I change the Tripod mode switch to toggle the ATTI mode), I could start my flight using regular GPS positioning and switch to ATTI mode if I see the GPS is weak or missing ?

I also read in the manual that “The aircraft automatically changes to Attitude (ATTI) mode when the Vision Systems are unavailable or disabled and when the GPS signal is weak or the compass experiences interference.”.  Does that mean I could just fly as usual (first safely, in the middle of the hole, far from the “walls”) and if the GPS signal ever gets lost the Mavic will switch automatically to ATTI mode ? This would allow me to avoid the “debug mode hack”…

So in short, could I just fly normally with a lot of caution, and be prepared that the drone my switch to ATTI mode at all time ?

Thanks!
2020-8-24
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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mr.jipi_ Posted at 8-24 04:59
Thank you for your help. Light shouldn't be a problem. It's a big hole and I can see the bottom without problem, but there is water.

On the Mavic 2 pro, ATTI mode I think must be enabled through the “debug mode”  using the Assistant App on a computer. This is something I haven’t done yet and I would need to train for that kind of flight.


So in short, could I just fly normally with a lot of caution, and be prepared that the drone my switch to ATTI mode at all time ?
If the pit is 40 metres wide and you stay well away from the sides, out in the open, you'll almost certainly have plenty of sats and there won't be any need to be concerned about atti mode.
The previous posts don't seem to realise how wide the pit is.

If you went down a narrow cut and lost most of the drone's skyview the number of sats your drone can see might drop past the minimum needed for maintaining GPS.
If that happens, your drone is in atti mode and has no horizontal position holding and no brakes.

If the pit has a vertical wall and you were close to that, you might lose enough sats to drop into atti mode, and you might not.
But if you are out in the open it should be no problem.
If you are concerned, just keep an eye on the number of sats the drone is connected to.

I've spent a lot of time in open cut coal mines and know there's unlikely to be any wind down there to worry about.
Take it easy, stay away from the sides and you'll have no problems.

Even if it did and you were well away from anything the drone could hit, it's still no problem as long as you use gentle input on the sticks.
And you could easily climb back to where GPS is available.
2020-8-24
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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mr.jipi_ Posted at 8-24 04:59
Thank you for your help. Light shouldn't be a problem. It's a big hole and I can see the bottom without problem, but there is water.

On the Mavic 2 pro, ATTI mode I think must be enabled through the “debug mode”  using the Assistant App on a computer. This is something I haven’t done yet and I would need to train for that kind of flight.

One final point, just because I can't see what it's like down there or know how far down you are going ...
Disable your downward facing sensors before the flight.
That will ensure you don't have any problem caused by this which is on p57 of your manual:
   Height is restricted to 16 ft (5 m) when the GPS signal is weak and Downward Vision System is activated.

   Height is restricted to 98 ft (30 m) when the GPS signal is weak and Downward Vision System is inactivated.

If the hole is as you described, there won't be any trouble at all.
I think when you mentioned the word mine, the others could only imagine a mineshaft tunnel and ignored the 40 metres width.

2020-8-24
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mr.jipi_
lvl.2
Flight distance : 73248 ft
Canada
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Labroides Posted at 8-24 06:39
One final point, just because I can't see what it's like down there or know how far down you are going ...
Disable your downward facing sensors before the flight.
That will ensure you don't have any problem caused by this which is on p57 of your manual:

Thank you very much for this in-depth answer Labroides,

When you say “Disable your downward facing sensors,” do you mean to turn off the “Enable Downward Vision Positioning” from the “Advanced Vision settings”? Or just turn off all the sensors at once ? Am I missing a more specific setting ?

I will still consider adding the ATTI mode to my controller as it seems a good safety measure and a great way to learn to fly like pros. I just wish I could keep both the sport and tripod mode at the same time.

Thanks
2020-8-24
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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mr.jipi_ Posted at 8-24 17:51
Thank you very much for this in-depth answer Labroides,

When you say “Disable your downward facing sensors,” do you mean to turn off the “Enable Downward Vision Positioning” from the “Advanced Vision settings”? Or just turn off all the sensors at once ? Am I missing a more specific setting ?

When you say “Disable your downward facing sensors,” do you mean to turn off the “Enable Downward Vision Positioning” from the “Advanced Vision settings”?
Yes
I was just being extra conservative in case the pit isn't as you described it.
But you probably won't be losing GPS anyway.

I will still consider adding the ATTI mode to my controller as it seems a good safety measure and a great way to learn to fly like pros.
You can if you really want to be able to access atti mode yourself.
But in the (unlikely) situation that you'd lose GPS, you don't have to switch to atti mode because atti mode is GPS mode without satellites.
2020-8-24
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DJI Paladin
Super Moderator
Flight distance : 318 ft

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Hi. Thank you for reaching out to DJI Forum. With regards to this matter. Please be cautious in this type of environment, there may be signal interference in the area that may affect the drone's GPS and remote's connectivity during flight. Thank you.
2020-8-25
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