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Compasses and GPS
792 13 2017-1-12
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GeoffN
lvl.4
Flight distance : 89564 ft
United Kingdom
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Phantom 3 Standard...............I'm a bit confused with GPS and Compass....................... flying drone today.....only the 2nd time...................In beginners mode and it was all working well and keeping me nearby............. the drone then gave up on me and it started running away from me.  A fast panic..... not a good thing!....... and desperately tried to get the thing to come back which resulted in me landing in some trees and having to go home and fetch a ladder!!

The log on the CJI app showed "magnetc field interference" and exiting GPS mode (after about 10 minutes flight)  which  I guess is why everything went wrong.

Any idea why this would happen as it was all working fine up to that point? I hadn't calibrated the compass as I was taking off from the same area I  have done before.

Am I right in thinking that if you lose the GPS, the return function/beginners mode just won't function and you have to bring it back manually, assuming you can still see it? If you can't see it, have you lost the drone for good? Will that little circular "radar like" symbol help guide you back if the gps fails or does that rely on it too?

What exactly does the compass do?  Can that help retrieve the drone if the GPS fails?

Sorry if these are daft questions!! I've studied the manuals and watched the videos.............. still don't quite get it I'm afraid.

Many thanks


2017-1-12
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Microcyb
First Officer
Flight distance : 1095955 ft
United States
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Did you insure the controller was in fact switched to GPS mode?
If you fly your bird around cell towers or places with a lot of steel and like power lines and buildings, you might lose your signal.
A1EFVior9BL._SL1500_.jpg


2017-1-12
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GeoffN
lvl.4
Flight distance : 89564 ft
United Kingdom
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Microcyb Posted at 2017-1-12 07:15
Did you insure the controller was in fact switched to GPS mode?
If you fly your bird around cell towers or places with a lot of steel and like power lines and buildings, you might lose your signal.
[view_image]

Defintely in  GPSmode to start with...... as I said, it was all working fine for the first 10 minutes when  it decided to abandon beginners mode and GPS.  The good thing is it had a softish landing in some trees that weren't too high. No building, anything nearby..... an open field with trees round the edge.
2017-1-12
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Vikassi
lvl.2
Flight distance : 17516 ft
United States
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Unfortunately, I had this happen in my backyard, lots of times.  I am near power lines, trees, and other houses.  From what others have told me, power lines do NOT affect the compass, supposedly that's a myth?  I have lost GPS with 10-11 Satellites, which I am also not sure how that's possible.  Are you flying in dense, populated areas?  
2017-1-12
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Vikassi
lvl.2
Flight distance : 17516 ft
United States
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Microcyb Posted at 2017-1-12 07:15
Did you insure the controller was in fact switched to GPS mode?
If you fly your bird around cell towers or places with a lot of steel and like power lines and buildings, you might lose your signal.
[view_image]

Did all those stickers come with your RC?  Mine does not have that and feel like that would be a HUGE plus if DJI added those by default.  Shocking that they don't considering how "dangerous" and "fragile" these things can be.
2017-1-12
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GeoffN
lvl.4
Flight distance : 89564 ft
United Kingdom
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Vikassi Posted at 2017-1-12 08:03
Did all those stickers come with your RC?  Mine does not have that and feel like that would be a HUGE plus if DJI added those by default.  Shocking that they don't considering how "dangerous" and "fragile" these things can be.

I was impressed with those too................. very handy for beginners like myself, in "panic mode"!!
2017-1-12
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Microcyb
First Officer
Flight distance : 1095955 ft
United States
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Vikassi Posted at 2017-1-12 08:03
Did all those stickers come with your RC?  Mine does not have that and feel like that would be a HUGE plus if DJI added those by default.  Shocking that they don't considering how "dangerous" and "fragile" these things can be.

You can get them here
Sticker Set ID Marking Decal for DJI Phantom 3 Standard Multifunction White
2017-1-12
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Microcyb
First Officer
Flight distance : 1095955 ft
United States
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GeoffN Posted at 2017-1-12 08:07
I was impressed with those too................. very handy for beginners like myself, in "panic mode"!!

Whole bunch of fun stuff on the web.
Sticker Set ID Marking Decal for DJI Phantom 3 Standard
2017-1-12
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GeoffN
lvl.4
Flight distance : 89564 ft
United Kingdom
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Microcyb Posted at 2017-1-12 08:12
Whole bunch of fun stuff on the web.
Sticker Set ID Marking Decal for DJI Phantom 3 Standard

found them in the uk here  http://www.ebay.com/itm/Sticker- ... Black-/262292941399                  must get some
2017-1-12
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solentlife
Captain
Flight distance : 1087530 ft
United States
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Basically when you lose GPS - the orientation and positional reference of the aircraft goes to crap.

The compass, when GPS is available is used in combination to guide in direction. GPS is unable to determine direction without 2 or more consecutive positions calculated. Imagine the aircraft trying to turn to direction without compass.

OK when GPS fails and you end up in plain mode - the trick is to try not panic. If you can see the aircraft - ease the stick forward to see which way she heads. You really have to just ease the stick and watch carefully. Since you have idea of which way - then rotate her slowly ... test again ... till you get her traveling back to you.
You may still have display of distance in your Go ... use this if sighting is too far. What you need to see is distance reducing. Do not worry about getting exact course back to you .... just get that distance to start reducing. Once you have that - maybe the map showing bottom left corner still has arrow and track ? That should help. Once distance starts coming down - and you bet better sight - you can then carefully rotate her to you.

This is where time spent learning yo fly the aircraft in good conditions pays off. Sorry to say it - but too many owners rely on the autonomous characteristics and never learn to fly it. When crap happens - they have no way to save it.

I practice this - even to flying in a room - which many say is not possible ... I suppose my history of normal RC fixed and rotary wing has instilled this in me.

Once people learn to fly the aircraft - I honestly believe their enjoyment increases. Their panic levels reduce.

Nigel
2017-1-12
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GeoffN
lvl.4
Flight distance : 89564 ft
United Kingdom
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solentlife Posted at 2017-1-12 10:27
Basically when you lose GPS - the orientation and positional reference of the aircraft goes to crap.

The compass, when GPS is available is used in combination to guide in direction. GPS is unable to determine direction without 2 or more consecutive positions calculated. Imagine the aircraft trying to turn to direction without compass.

Thanks Nigel..... that's really helpful...... don't panic seems a major thing!    Didn't realise the distance "monitor" or the map might still work without the GPS............. I just imagined that once out of sight, you'd were in trouble.  Once I'm a bit better with things, I'll try practicing without the GPS. In the mean time....I mustn't panic!   I think I just panicked and pulled the left stick down to try and get the drone down as quick as possible......... with hindsight, should have done the opposite and then slowly bought it back.   Thanks again
2017-1-12
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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GeoffN Posted at 2017-1-12 12:16
Thanks Nigel..... that's really helpful...... don't panic seems a major thing!    Didn't realise the distance "monitor" or the map might still work without the GPS............. I just imagined that once out of sight, you'd were in trouble.  Once I'm a bit better with things, I'll try practicing without the GPS. In the mean time....I mustn't panic!   I think I just panicked and pulled the left stick down to try and get the drone down as quick as possible......... with hindsight, should have done the opposite and then slowly bought it back.   Thanks again

You've been given confusing advice.
If you lose GPS your Phantom doesn't know where it is and so can't relay a distance to your app.

To get back to your original issue ....
If the Phantom has conflicting data from the compass and GPS, it drops the GPS data and leaves you in atti mode with no position holding ability, no brakes and able to drift with the wind if you don't control it.

That's what happened to your Phantom.
The Magnetic Field Interference warning is telling you that the compass has detected a magnetic field that is different from what it was calibrated for.
Unless you fly very close to a lot of steel (like descending to a metre above a steel roof) or close to a high voltage cable, the two causes of this are a bad compass calibration or a bad compass.

You mentioned calibrating the compass before the flight.
This may be the cause
of the incident.
Where did you calibrate it?
Was it close to a car, structural steel or reinforced concrete?
How far from calibration point did the error message appear?

And ... you shouldn't be recalibrating your Phantom every time you fly.
That only increases the risk of getting a bad compass calibration.
Get a good calibration and stick with it.

If you want more details of your problem flight Go to http://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions to upload your flight record.
2017-1-12
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solentlife
Captain
Flight distance : 1087530 ft
United States
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Labroides - I did say MAY STILL have distance display - based on losing compass not GPS.

Also it is advised by DJI to INCREASE altitude and hover if compass error - so that any influence is weaker and GPS can lock in .... the aircraft will then hopefully reset. Its in the manual.
Nigel
2017-1-12
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Vikassi
lvl.2
Flight distance : 17516 ft
United States
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solentlife Posted at 2017-1-12 16:40
Labroides - I did say MAY STILL have distance display - based on losing compass not GPS.

Also it is advised by DJI to INCREASE altitude and hover if compass error - so that any influence is weaker and GPS can lock in .... the aircraft will then hopefully reset. Its in the manual.

Yea, I would agree, if you're in a bad spot, and you get a compass error, take her up in the air.  
2017-1-12
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