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IMU not allowing hand launch off moving vessel
1110 8 2021-6-29
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MTengineer
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Flight distance : 5722185 ft
United States
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Hi there,
I'm flying a Mavic 2 Pro and Zoom off of a moving vessel and more and more often the drone will not let me launch. It gives me an error saying "Navigation System Error" and when I go to the IMU page rather than Healthy, Unhealthy, etc it just shows "Moving" for all parameters and it won't let me take off. I calibrated my IMU on land but we are sailing all over the world often for weeks at a time without access to land so if it gets in this state I often don't have land nearby to do an IMU calibration.

I've been flying for 6 years with multiple variations of DJI hardware and would consider myself an advanced pilot. Only with the most recent Mavic 2 Pro and Zoom models have I had constant issues. I am doing hand launches and retrievals as it's required if I want to get any of the incredible footage of us under sail. The new Mavic 2 models seem to be too smart for their own good and I've missed out on numerous shots because the damn thing won't let me get into the air. The only way to trick it that I've discovered thus far is to hold onto the drone while inside the boat which forces it into No Position ATTI mode. I then "launch" the drone while still holding on tight (blades spinning) as it tries to fly out of my fingers, walk outside, and let it go off the back of the boat. I'm comfortable launching and landing in sketchy situations but this pushes my limits and I feel like there has to be a better way.

I tried the "hack" of forcing the drone into ATTI mode but unfortunately this ATTI mode isn't the same as the "No Position ATTI Mode" as it still won't allow takeoff because it sees the Moving IMU state. Are there any workarounds out there? I can't be the only mariner who is running into this, surely?

Lars
2021-6-29
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GaryDoug
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Flight distance : 1264639 ft
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United States
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I  can't answer your question because I have never tried to launch while underway. But have you tried to luff up to stop the boat temporarily? Not the ideal method I suspect.
2021-6-29
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Geebax
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Australia
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It certainly sounds like the software engineers at DJI have been drinking the Apple Koolaid. "We know better than you do, so we will protect you from yourself"
2021-6-29
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Labroides
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Flight distance : 9991457 ft
Australia
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so if it gets in this state I often don't have land nearby to do an IMU calibration.
Your IMU is already calibrated, recalibrating it won't make any difference.
Normally, there's no need to ever recalibrate the IMU unless the drone has been in a bad crash.

I tried the "hack" of forcing the drone into ATTI mode but unfortunately this ATTI mode isn't the same as the "No Position ATTI Mode" as it still won't allow takeoff because it sees the Moving IMU state. Are there any workarounds out there? I can't be the only mariner who is running into this, surely?

Hard to see how your indoor atti trick would allow takeoff if outdoor doesn't.
The accelerometers in the IMU should still sens the same thing.
I've launched Phantoms from moving boats by switching to atti mode to prevent the drone from fighting to hold position before launch.

How about heaving to, then launch, then sail away?

2021-6-29
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MTengineer
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Flight distance : 5722185 ft
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Labroides Posted at 6-29 21:19
so if it gets in this state I often don't have land nearby to do an IMU calibration.
Your IMU is already calibrated, recalibrating it won't make any difference.
Normally, there's no need to ever recalibrate the IMU unless the drone has been in a bad crash.

Neither my Mavic 2 Pro or Zoom have ever been in a crash but the IMU error still occurs and is much more frequent whenever I'm in swelly seas. Have you personally flown your drone much in the open ocean? Unfortunately what holds true on land doesn't play the same when you're talking about flying in 3-4m (9-12ft) swell.

As for the trick of "launching" the drone indoors and walking it outside I can only report that is is indeed the case that the No Position ATTI mode does ignore the IMU sensor state.  I have personally tested it between the "hacked" ATTI mode and the No Position ATTI mode at sea and one works and one doesn't. This is currently my only functioning workaround when I want to launch while in heavy swell.

Lastly, heaving to on the sailboat does not do anything about the swell of the ocean and it's impact on the IMU in my experience. I would even argue that a sailboat under way has far less motion when it's slicing through the water than when it's bobbing hove-to. Plus this is often far easier said than done if we have a spinnaker out or are on a big downwind run and I'm missing out on these shots because of this flaw in the firmware.

Lars
2021-6-30
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Labroides
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Flight distance : 9991457 ft
Australia
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MTengineer Posted at 6-30 20:53
Neither my Mavic 2 Pro or Zoom have ever been in a crash but the IMU error still occurs and is much more frequent whenever I'm in swelly seas. Have you personally flown your drone much in the open ocean? Unfortunately what holds true on land doesn't play the same when you're talking about flying in 3-4m (9-12ft) swell.

As for the trick of "launching" the drone indoors and walking it outside I can only report that is is indeed the case that the No Position ATTI mode does ignore the IMU sensor state.  I have personally tested it between the "hacked" ATTI mode and the No Position ATTI mode at sea and one works and one doesn't. This is currently my only functioning workaround when I want to launch while in heavy swell.

Neither my Mavic 2 Pro or Zoom have ever been in a crash but the IMU error still occurs and is much more frequent whenever I'm in swelly seas.
The IMU "error" is not indicating a fault in the IMU.
It's the IMU warning you that conditions are not suitable for launching.

Have you personally flown your drone much in the open ocean?

Yes ... it's only rarely that I fly on land.
2021-7-1
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FB: GeoDrone4K
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Flight distance : 1532264 ft
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Romania
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I have launched A2S without problems from hand from a moving boat. Was set to hoover if signal is lost, also was in back of boat without metal objects around. Was fine, no IMU or other errors received.
The boat was on sails at that moment, not engine, so probably advancing with 2-2.5 knots.
Cheers.
2021-7-1
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MTengineer
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Labroides Posted at 7-1 00:00
Neither my Mavic 2 Pro or Zoom have ever been in a crash but the IMU error still occurs and is much more frequent whenever I'm in swelly seas.
The IMU "error" is not indicating a fault in the IMU.
It's the IMU warning you that conditions are not suitable for launching.

Thanks for the reply. The strange thing is that this is happening with two separate DJI drones aboard and I've encountered it before with another drone that we briefly had aboard. Two of them were DJI Mavic Pro 2's and one was a DJI Mavic Pro Zoom. If it was specific to the IMU then I can't understand why it would be happening on so many different units. All had their IMUs calibrated on land following proper procedures.

Note that we had both a DJI Mavic Pro (not 2 Pro or 2 Zoom) on the vessel in the past and had no issues. Also the "Navigation System Error" is truly more of a warning as it will go away if we tuck into a bay and thus reduce the swell of the boat. It's labelled an Error on the main screen most likely because warnings typically still allow you to fly but this one is preventing launch.

The "Moving" status on the IMU calibration page is the cause of the "Nav System Error" and when this goes back to Healthy/Unhealthy with the status bar then I can fly again.
2021-7-1
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808_inspire
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Flight distance : 34259 ft
United States
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I have the same problem with a phantom 4 Pro v2.  The IMU won't initialize anymore when on a boat.  I can get it to fly from land, but not from a boat anymore.  I fly pretty much only from a boat, and this never happened before.  And older phantom 4 still can fly from a boat, as well as an Inspire...
Has a fix been found yet?
2021-7-5
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