Unable to launch drone in the dark

djiuser_p1MHy4hMCWi7

Hi guys

Yesterday I wanted to test some things with a Lume Cube attached to my Mavic 3.
Close to the house, there was a light on the terrace and I could launch my drone.
But when I turned off the light, the drone would not start.

On my controller I got the message to calibrate the compass?! Now my question is, does the darkness have anything to do with calibrating the compass?
Are those two related?

Thank you in advance.

JJB*

Hi,

No not related in any way !!

Most likely the Lume Cube disturbed the compass.

cheers
JJB

djiuser_p1MHy4hMCWi7

JJB* Posted at 9-24 00:49
Hi,

No not related in any way !!

Thank you, for your quick reply!
I had the Lime Cube attached on top of the drone. Can there be a difference if I mount it "under" the drone?

JJB*

djiuser_p1MHy4hMCWi7 Posted at 9-24 00:55
Thank you, for your quick reply!
I had the Lime Cube attached on top of the drone. Can there be a difference if I mount it "under" the drone?

i have no idea

Wow, on top....really close to the compass.

But an internal magnet (inside cube) close to a compass is not a good idea!
You can always give it a try bottom side ( mayby remove the cube magnet ? )

Good compass functioning in a DJI drone is vital for god flight, so be carefull...

cheers
JJB

djiuser_p1MHy4hMCWi7

JJB* Posted at 9-24 01:00
i have no idea

Wow, on top....really close to the compass.

Thanks JJB, I'm going to give It another try attached under the drone.
I'll keep you posted.

Labroides

On my controller I got the message to calibrate the compass?! Now my question is, does the darkness have anything to do with calibrating the compass?
Are those two related?

The message is completely fake news and DJI should be ashamed to give users incorrect information like that.
There is nothing at all wrong with your compass and it does not need recalibrating.
It also has nothing to do with the accessory you have fitted.

I've run into this a couple of times and eventually worked it out.

If you get a strong flashlight and light the area around the drone, you'll find the false warning doesn't appear and you can launch without problems.

djiuser_p1MHy4hMCWi7

Labroides Posted at 9-24 01:16
On my controller I got the message to calibrate the compass?! Now my question is, does the darkness have anything to do with calibrating the compass?
Are those two related?

Okay!!!
Thanks, that's new to me.
I'm going to try it out - thanks man.

JJB*

Labroides Posted at 9-24 01:16
On my controller I got the message to calibrate the compass?! Now my question is, does the darkness have anything to do with calibrating the compass?
Are those two related?

True, mounting external items to a drone does not effect the compass.
But what if this light has a internal magnet and was put on top of his drone?

FlyApp has no eyes to check if something is on or near the drone ....So if the software shows a compass calibration message it means that something has changed to the previous flights.
Not surprised to read that the software shows a compass calibration message (if that light has a magnet in the housing, as i read on the www)

cheers
JJB

Sean-bumble-bee

With regards to taking off in darkness, aside from illuminating the ground with a torch etc, have a look at the first sentence of the second paragraph of post #2 in the thread https://forum.dji.com/forum.php?mod=viewthread&tid=297892 . If the link does not work the thread is in Mavic Mini forum and entitled "The Mini flashes red".

If the Mavic 3 behaves in the same way as a Mavic 2 it will probably switch its "auxiliary bottom light" on soon after take off.
Be aware that if the ground is NOT illuminated, by whatever means, the drone will be relying on GPS position holding ALONE and GPS position holding IS NOT as accurate as VPS position holding i.e. the drone may drift somewhat.
DO NOT launch the drone with poor GPS since, without sufficient illumination of the ground i.e. no VPS, the drone will enter ATTI flight mode.

Labroides

JJB* Posted at 9-24 01:59
True, mounting external items to a drone does not effect the compass.
But what if this light has a internal magnet and was put on top of his drone?

True, mounting external items to a drone does not effect the compass.
Mounting accessories could affect the compass, but in this case I don't believe it's the issue.

FlyApp has no eyes to check if something is on or near the drone ....So if the software shows a compass calibration message it means that something has changed to the previous flights.
You would think so, but I have had similar experiences to the OP, except without any modification of my Mavic 3 and 3 pro.
In both cases, I had flown in late afternoon and could not launch later after dark from the same places which I knew had no magnetic interference.
Because of the magnetic interference message, I tried moving to other nearby locations and each time, I had the same fake message about the compass.
Checking the orientation of the drone vs the drone icon on the map, confirmed there was no magnetic issue.

The only thing that had changed was the ambient light.

The second time I ran into this problem, I tapped on the compass calibration warning and looked into the actual message and found the clue that it was all about the lighting, not the compass.
DJI's screen warning message is worse than misleading.

I tried illuminating the launch spot with a flashlight and that solved the issue.

DJI Tony

Hello there. Thank you for reaching out. JJB* is correct. The compass does not relate to the light. We have not optimized the Mavic 3 to be used with third-party accessories and we don't advise it because we cannot guarantee flight safety. We appreciate your valued support and understanding.

JJB*

Labroides Posted at 9-24 12:25
True, mounting external items to a drone does not effect the compass.
Mounting accessories could affect the compass, but in this case I don't believe it's the issue.

Why this conclusion?

True, mounting external items to a drone does not effect the compass.
Mounting accessories could affect the compass, but in this case I don't believe it's the issue.
If this, see pic, is mounted on top of a drone, than ofcourse a compass calibration is seen in the app.
The housing of this cube light has a magnet in it, handy to attach to iron objects.
Magnets close to the compass of a drone isn`t a good idea.
Curious to know why you do not think it`s the issue, more bc you think than mounting accessories could affect the compass (uh?) but not in this case while a magnet was close to the DJI compass.

But agree on this 'incorrect ' warning text, DJI should explain this.
cheers
JJB

JJB*

DJI Tony Posted at 9-24 20:21
Hello there. Thank you for reaching out. JJB* is correct. The compass does not relate to the light. We have not optimized the Mavic 3 to be used with third-party accessories and we don't advise it because we cannot guarantee flight safety. We appreciate your valued support and understanding.

Hi Tony,

Your text : "The compass does not relate to the light"

So can you explain this warning?

Compass error + Unable to take off in low light environment.

cheers
JJB

DJI Tony

JJB* Posted at 9-24 23:03
Hi Tony,

Your text : "The compass does not relate to the light"

Hello, JJB.This just simply means you can't fly in a lowlight environment and a compass error. Have a great day ahead.

Labroides

JJB* Posted at 9-24 22:55
Why this conclusion?

True, mounting external items to a drone does not effect the compass.

Why this conclusion?
I made an effort to explain that quite clearly.

JJB*

Labroides Posted at 9-25 02:19
Why this conclusion?
I made an effort to explain that quite clearly.

No, imo you did not explain why in his case you don`t believe it is the issue.
You just assume that your experience with such error equals his error.

cheers
JJB

Labroides

JJB* Posted at 9-25 05:02
No, imo you did not explain why in his case you don`t believe it is the issue.
You just assume that your experience with such error equals his error.

You are the one assuming that the issue I dealt with and solved isn't the same as what the OP encountered.
You mightn't be able to understand that, but I don't care.

bjr981s

JJB* Posted at 9-25 05:02
No, imo you did not explain why in his case you don`t believe it is the issue.
You just assume that your experience with such error equals his error.

Hi JIB,

Here is some input from a 40 year RC Pilot, Fixed wing, Helicopter and turbine, and a DJI pilot for 10 years and an electronics engineer.

Some rules and some observation on the OP issues.

Never attempt to takeoff from an area that is close to metal. E.g. the roof of a car. It will impact the compass at time of launch and you will get compass errors for the remainder of the flight. Steel rods in concrete slabs will do the same. The error in the compass is small enough that your flight will be OK but the heading of the drone at low speed will be off by a few degrees. It can cause the drone on a RTH flight to miss the waypoint radius and fly away. Many issues like this have happened and been reported over the years on this forum. Less however since DJI have been enhancing the technology and FW logic in the drones.

You will also see this same error happing if you have not calibrated your drone for your physical location on the planet. The GPS coordinates do not correlate to a correct vector, if the compass is in error.

The GPS map north, points to True North the compass to Magnetic North.

Doing hyperlapses and waypoint based slow flight will be out of location as the GPS only provides a true north heading when flying at speed. The compass is used in these conditions and if you have not done a local calibration it will be many degrees out depending on your location. I can post you a link to the online documentation of this if required and you can determine the compass error for your location. The compasses are calibrated at the factory. You should always do one for your home location. IMU calibration is not necessary unless you have crashed your drone.

The Compass error displayed by the App is when you have a gross compass error, it advises for a recalibration. In most cases moving away from the interference source is enough for the drone to recover its bearings after a power reset.

On some previous models DJI implemented a timer to force a compass recalibration after a specific set time. I don't believe that is done on recent generation drones.

These is where its hard to provide advice as the factors change between drone generations.

Now as to the OPs issues. He has many.

Firstly he has placed a strong magnet directly over the GPS / IMU this will cause the compass to complain and request that it be recalibrated.

Secondly he has placed a RF shield directly over the GPS antenna.Blocking the acquisition of satellites.

Starting the drone without a good GPS lock it will rely on the optifow of the downward vision sensors. Doing this in the dark the sensors have no light. So it does not want to start on vision mode.

Activating the OEM downward light will assist but only at low altitude above the vision sensor limit the drone will badly drift in the wind.

Adding any non OEM DJI componentry is ill advised unless you understand the technology and the consequences fully.

i hope this little essay will assist.

Cheers

JJB*

bjr981s Posted at 9-25 06:50
Hi JIB,

Here is some input from a 40 year RC Pilot, Fixed wing, Helicopter and turbine, and a DJI pilot for 10 years and an electronics engineer.

Hi,

Thanks for your long essay ;-)

But nothing in your text is new knowledge for me, but thanks anyhow.
Never attempt to takeoff from an area that is close to metal. E.g. the roof of a car. It will impact the compass at time of launch and you will get compass errors for the remainder of the flight **. Steel rods in concrete slabs will do the same. The error in the compass is small enough that your flight will be OK but the heading of the drone at low speed will be off by a few degrees. It can cause the drone on a RTH flight to miss the waypoint radius and fly away

** when powering ON a DJI drone the compass heading is used also for gyro heading setting. If compass is offset due to magn interference than after takeoff the compass (away from that magn interference) compass is indication the correct heading. But the gyro is not resetted to this correct heading value!
If auto position corrections by software has to be made than the wrong motors are used for making the position correction. Thus drone is not correction towards the old position but steer/fly into to wrong direction, thus more offset from position, more incorrect corrections, etc etc. Fly Away !
This will for 98% happens shortly after takeoff. I never saw a flightrecord in wich during a RTH drone had a fly away.
What i have seen in fly aways in flightlogs ; when during a fly away (compass/yaw errors) RTH was selected, in some cases the yaw mismatch was 'repaired' and drone fly away was stoppend, drone into RTH and landed safely at HP.

IMO the most important check on DJI drones (for each flight always) is to check blue compass arrow heading in the map view FlyApp (default N up) and compare this heading with the actual heading. If not the same : Do NOT Fly ( power OFF drone, move to another location, power ON and check again)

cheers
JJB

Mobilehomer

JJB* Posted at 9-24 22:55
Why this conclusion?

True, mounting external items to a drone does not effect the compass.

I think you are looking at the wrong LumeCube. This is the one for drones. No magnet.

JJB*

Mobilehomer Posted at 9-25 07:26
I think you are looking at the wrong LumeCube. This is the one for drones. No magnet.[view_image]

thanks, mayby your are correct.

But these are called Lume Cube Strobe, OP writes only Lume Cube.
If this is the one than ofcourse no magnet to interfere with the drone compass, if this small light will interfere with compass (was mounted on top of his drone) i don`t know. (probably not)

cheers
JJB

Mobilehomer

JJB* Posted at 9-25 07:44
thanks, mayby your are correct.

But these are called Lume Cube Strobe, OP writes only Lume Cube.

This is the one lots of people use. I prefer the Firehouse Arc 5.

Labroides

I've read of many flyers using small strobes on their drones, but never seen a report of any of them having compass issues.
I've had the same issue that the OP posted about in two locations where there was no magnetic interference and initially believed the warning was about magnetic interference, but eventually looked into the warning message further and found that it's got nothing to do with magnetic interference and is all about low light levels.
I proved that illuminating the launch spot solves the issue.
It's very simple. - the wording on the full warning tells what it's about.
Why is it so hard for one or two experts (in their own minds) to understand?
They are completely distracted by the poor wording of DJI's message, but still can't see past that when the facts are handed to them on a plate.

djiuser_p1MHy4hMCWi7

JJB* Posted at 9-25 07:44
thanks, mayby your are correct.

But these are called Lume Cube Strobe, OP writes only Lume Cube.

I also have this light in my possession.
It's called the anti-collision light, not?

An advantage of the Lime Cube is that you can turn on or off the light using an app on your smartphone.
So you can fly to the required position, light the cube, do your thing while the shutter of your camera is open, turn off the light and return. So there's no other light interfering your photo...

That's unfortunately not possible with the anti-collision light.

JJB*

djiuser_p1MHy4hMCWi7 Posted at 9-26 00:44
I also have this light in my possession.
It's called the anti-collision light, not?

Hi,

so wich light did you mount on top of your drone, the anti coll light or the one as in post #12 ?

cheers
JJB

djiuser_p1MHy4hMCWi7

JJB* Posted at 9-26 03:08
Hi,

so wich light did you mount on top of your drone, the anti coll light or the one as in post #12 ?

The Cube.

JJB*

djiuser_p1MHy4hMCWi7 Posted at 9-28 00:19
The Cube.
[view_image]

thanks....that explains your compass issue