Flying in Iceland, mag interference, ATTI mode.

Pedro · Feb 21, 2017

I'm travelling to Iceland in just over 3 weeks tme and, subject to the weather, I shall be flying the Mavic, a lot..

I've heard from a number of sources that magnetic interference may be an issue in Iceland due to its latitude and ground make up, see here: SKYPIXEL.ORG - Aerial drone photography near the arctic circle. I...

This will be 5hit or bust trip for my Mavic as I don't see the point of not letting it spreads it wings and exploring its full potential, well and mine of course.

So if I'm a mile out and I get mag interference and she switches to ATTI (I believe that is what will happen in those circumstances), will I lose her location on the map? I'm quite happy to fly ATTI, that's all I've done for the past 3 years before getting a Mavic.

Should I consider blocking the GPS reception and just fly ATTI from the outset and just rely upon the video feed to fly? Avoid TBE, etc.?

Thanks.

Gernby · Feb 21, 2017

If you are able to block GPS mode somehow, that would be good for indoor flights too. I wonder if you could do it by taping a magnet somewhere on the body.

AlanTheBeast · Feb 21, 2017

Pedro said:
I'm travelling to Iceland in just over 3 weeks tme and, subject to the weather, I shall be flying the Mavic, a lot..

I've heard from a number of sources that magnetic interference may be an issue in Iceland due to its latitude and ground make up, see here: SKYPIXEL.ORG - Aerial drone photography near the arctic circle. I...

This will be 5hit or bust trip for my Mavic as I don't see the point of not letting it spreads it wings and exploring its full potential, well and mine of course.

So if I'm a mile out and I get mag interference and she switches to ATTI (I believe that is what will happen in those circumstances), will I lose her location on the map? I'm quite happy to fly ATTI, that's all I've done for the past 3 years before getting a Mavic.

Should I consider blocking the GPS reception and just fly ATTI from the outset and just rely upon the video feed to fly? Avoid TBE, etc.?

Thanks.

seems to be fine.
make that damned fine.

The latitude of Iceland should still make a magnetic compass useable for navigation (vice grid north).

This has nothing at all to do with GPS. GPS will give accurate location and very good altitude there. Indeed with the MP's SBAS receiver (EGNOS/GPS) it will be receiving corrections for both GPS and GLONASS making it pretty accurate most of the time (5m or better almost 100% of the time; 2m or better 90% of the time).

I don't think you'll have any issues other than possibly needing to calibrate mag from time to time due to localized effects.

AlanTheBeast · Feb 21, 2017

Gernby said:
If you are able to block GPS mode somehow, that would be good for indoor flights too. I wonder if you could do it by taping a magnet somewhere on the body.

GPS doesn't give a crap about magnets. You can (allegedly) block the GPS antenna with some tinfoil. Offhand I don't know where the GPS antenna is! (Front or back).

Pedro · Feb 21, 2017

AlanTheBeast said:
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seems to be fine.

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make that damned fine.

The latitude of Iceland should still make a magnetic compass useable for navigation (vice grid north).

This has nothing at all to do with GPS. GPS will give accurate location and very good altitude there. Indeed with the MP's SBAS receiver (EGNOS/GPS) it will be receiving corrections for both GPS and GLONASS making it pretty accurate most of the time (5m or better almost 100% of the time; 2m or better 90% of the time).

I don't think you'll have any issues other than possibly needing to calibrate mag from time to time due to localized effects.

Many thanks Alan, that's very reassuring.. I'll stop worrying (so much) now..

I just hope we get some decent weather too.

Pedro · Feb 28, 2017

Being a worrier, I just read the article linked in my first post above again and read this part:

"Further complicating the magnetic environment is the huge amount of volcanic rock, which basically makes up the entire island. The minerals spewed by volcanos can end up being incredibly magnetic, which can also influence compass readings. The way the complex magnetic environment manifests itself during GPS-based multicopter flight is that GPS hold becomes less effective. In a few locations around the island, my Phantom 2 began to “toilet bowl,” which means that it started to drift in a circle even when it was supposed to be holding position. This drift was easy to correct because I am a competent pilot, and helping the Phantom to stay in the same place by manually piloting kept it under control. However, if the drifting was left uncorrected, the Phantom would start to drift in wider and wider circles, flying faster and faster. I hate to imagine what would have happened if I had been unable to correct for this! In the worst case, which happened on a large plain on the Snæfellsnes peninsula, I had to switch into ATT mode to control the quadcopter, which instantly stopped the toilet bowling, but of course prevented GPS-assisted flight. The point here is that you should be a good pilot before attempting to fly any multicopter in GPS-assisted modes in magnetic environments like this. At a minimum, you shouldn’t have to think to convert desired muticopter motion into radio stick movements, and you should be very comfortable flying in ATT mode, even in wind."

So if I do experience mag interference, firstly she won't take off so I guess I just move about a bit until she does. But if I do experience bad mag in flight, as I can't switch to ATTI with the Mavic, I suppose I'll have no choice but to try to bring her back to land. The article implies that by coming out of GPS mode it cures the issue but as Alan states above, GPS is different to the magnetometer so why would that help? Prevents contradicting signals maybe?

I just want to be aware of what if any options I have to prevent her disappearing down a volcano. Thanks for any input.

AlanTheBeast · Feb 28, 2017

Pedro said:
Being a worrier, I just read the article linked in my first post above again and read this part:

"Further complicating the magnetic environment is the huge amount of volcanic rock, which basically makes up the entire island. The minerals spewed by volcanos can end up being incredibly magnetic, which can also influence compass readings. The way the complex magnetic environment manifests itself during GPS-based multicopter flight is that GPS hold becomes less effective. In a few locations around the island, my Phantom 2 began to “toilet bowl,” which means that it started to drift in a circle even when it was supposed to be holding position. This drift was easy to correct because I am a competent pilot, and helping the Phantom to stay in the same place by manually piloting kept it under control. However, if the drifting was left uncorrected, the Phantom would start to drift in wider and wider circles, flying faster and faster. I hate to imagine what would have happened if I had been unable to correct for this! In the worst case, which happened on a large plain on the Snæfellsnes peninsula, I had to switch into ATT mode to control the quadcopter, which instantly stopped the toilet bowling, but of course prevented GPS-assisted flight. The point here is that you should be a good pilot before attempting to fly any multicopter in GPS-assisted modes in magnetic environments like this. At a minimum, you shouldn’t have to think to convert desired muticopter motion into radio stick movements, and you should be very comfortable flying in ATT mode, even in wind."

So if I do experience mag interference, firstly she won't take off so I guess I just move about a bit until she does. But if I do experience bad mag in flight, as I can't switch to ATTI with the Mavic, I suppose I'll have no choice but to try to bring her back to land. The article implies that by coming out of GPS mode it cures the issue but as Alan states above, GPS is different to the magnetometer so why would that help? Prevents contradicting signals maybe?

I just want to be aware of what if any options I have to prevent her disappearing down a volcano. Thanks for any input.

I think it's because DJI do not integrate the GPS with the compass very well. The GPS can give direction of movement at all times. Coupled with the IMU they should not only be able to ignore a wonky compass, but also re-calibrate on the fly. Indeed we (at the co. I worked) calibrated out mag compass errors on helicopters using a Kalman filter and GPS (CF-UTTH program) [Peter H. was the engineer]. This made the Doppler radar nav system more accurate.

Reading that article is indeed sobering. So maybe rehearse your navigation skills and ability to bring the bird back in ATTI. Don't let it get too far out.

Pedro · Feb 28, 2017

Thanks Alan. I'm quite happy flying in ATTI as long it does what I tell it to. All my other dozen or so drones I've built and flown have all been flown in attitude mode, this is the first DJI product I've had since my very first multirotor 3 or so years ago, a Phantom 1. Since then I've flown all sorts of FCs, Pixhawk, Brainfpv, CC3D, Revo Nano, etc.

AlanTheBeast · Feb 28, 2017

Pedro said:
Thanks Alan. I'm quite happy flying in ATTI as long it does what I tell it to. All my other dozen or so drones I've built and flown have all been flown in attitude mode, this is the first DJI product I've had since my very first multirotor 3 or so years ago, a Phantom 1. Since then I've flown all sorts of FCs, Pixhawk, Brainfpv, CC3D, Revo Nano, etc.

Then you're way ahead of me! I just see the sole "magnetic" issue in Iceland to be high variability and the MP should be able to cope but I guess DJI depend an awful lot on the mag compass for heading and don't take advantage of all their other magnificent sensors. (S/w is expensive to design, code and especially test).

What I found comforting (and I'm sure you do too) is those videos. So doable - with appropriate caution and backup plans(s).

I envy you - I'd love to go there!

Pedro · Feb 28, 2017

Thanks again, yes the videos look great.. Am super excited about going.

gregw · Feb 28, 2017

I remember reading a post in that ultra-long thread over at RCGroups, someone tested that doing a complete 360 degree yaw when encountering TBE is a possible solution to weird/problematic compass during flight... Not sure if that will absolutely cure the problem, but just something to keep in mind just-in-case of a worse case scenario...

Tried looking for that post, but can't find it at the moment... I'll update this post if/when I find it.

Pedro · Mar 1, 2017

Thanks for that Greg, have filed it in the emergency/panic/wtf memory bank.

Tanguy · Mar 25, 2017

Hello Pedro any feedback on your flying experience in Iceland? I am going next week and hope I can get nice shoot with my MP.

mlaczek · Mar 25, 2017

AlanTheBeast said:
GPS doesn't give a crap about magnets. You can (allegedly) block the GPS antenna with some tinfoil. Offhand I don't know where the GPS antenna is! (Front or back).

i found some informatin from here about the GPS antenna.

he said: "it's at the back of the aircraft on the top half of the shell behind the battery compartment."

Pedro · Mar 25, 2017

Tanguy said:
Hello Pedro any feedback on your flying experience in Iceland? I am going next week and hope I can get nice shoot with my MP.

You'll have a superb time IF the weather is favourable.. We were so lucky to have 3 beautifully sunny days with good but variable winds but when it blows you know about it. I had no mag interference whatsoever despite kp being up to 4 on a couple of occasions. Your main issue is likely to be wind. My Mavic coped admirably with the wind and cold, one on occasion we stopped on our way back to our cabin and it was blowing at least 20mph with gusts a lot higher and it was -3C and she did just fine. Stupidly I forgot to put my gloves on and after 4 or 5 minutes they were killing.

In hindsight I regret not being a little more daring with some of my flying but when your Mavic is a mile or more away from you over a massive glacier lagoon 600 feet up, at the time it did feel pretty daring!

I'm doing some editing of the videos now so I will start a thread once done and give a longer account of our trip. Suffice to say we absolutely love Iceland now and cannot wait to go back.

This is a little taster, just a few ungraded clips:

AlanTheBeast · Mar 25, 2017

Green with envy here! Well done!

mlaczek · Mar 25, 2017

Pedro said:
You'll have a superb time IF the weather is favourable.. We were so lucky to have 3 beautifully sunny days with good but variable winds but when it blows you know about it. I had no mag interference whatsoever despite kp being up to 4 on a couple of occasions. Your main issue is likely to be wind. My Mavic coped admirably with the wind and cold, one on occasion we stopped on our way back to our cabin and it was blowing at least 20mph with gusts a lot higher and it was -3C and she did just fine. Stupidly I forgot to put my gloves on and after 4 or 5 minutes they were killing.

In hindsight I regret not being a little more daring with some of my flying but when your Mavic is a mile or more away from you over a massive glacier lagoon 600 feet up, at the time it did feel pretty daring!

I'm doing some editing of the videos now so I will start a thread once done and give a longer account of our trip. Suffice to say we absolutely love Iceland now and cannot wait to go back.

This is a little taster, just a few ungraded clips:

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WOW!!!

AJMavicpilot · Mar 25, 2017

Was flying my Mavic in Iceland this January had no problems other than being spoilt for choice in what to film. As mentioned before when the wind blows it blows hard! Other than that enjoy and be sure to do the golden Circle.