Compass Issue on Bridge

[bkushner]

Two times I attempted to fly my drone from a location on top of a bridge. There is a visitors center on the bridge and you can fly from the parking lot.

First time I did not get GPS lock and had calibrate compass. Today I tried again. I had GPS but the compass warning again. Lifted off the ground and the bird went nuts. Almost impossible to control. Just going every which way imaginable. I was only at about 20 feet. After a crazy struggle I got it down on the ground.

I'm assuming the bridge has heavy metal content. However, others fly there...is there something I can be doing wrong?

I can't calibrate compass there it fails..

 

[Fly Dawg]

Calibrating the compass has nothing to do with GPS lock. But calibrating the compass any where near the metallic structure does. I have flown through old covered bridges before, in ATTI of coarse, but all that metal does affect the compass significantly.

 

[lickitysplit11111]

Two times I attempted to fly my drone from a location on top of a bridge. There is a visitors center on the bridge and you can fly from the parking lot.

First time I did not get GPS lock and had calibrate compass. Today I tried again. I had GPS but the compass warning again. Lifted off the ground and the bird went nuts. Almost impossible to control. Just going every which way imaginable. I was only at about 20 feet. After a crazy struggle I got it down on the ground.

I'm assuming the bridge has heavy metal content. However, others fly there...is there something I can be doing wrong?

I can't calibrate compass there it fails..

This sounds like what happened to me at the same location on two separate days I was in GPS at launch then right after take-off I received 4 error messages and the copter went into Atti mode the alarms were goin off pop-ups the first time it happened once I got about 100 ft away from the launch point it went back into GPS and I flew a normal flight and landed without issue , I just dont launch at that spot no more the risk ain't worth it .
Here's a pic of the object on the pier of what I believe cause it. A sundial.

 

[With The Birds]

Calibrating the compass at your launch point in these circumstances is ill advised. You would likely have found that had you stuck to your existing calibration all would have been good once you were in the air clear of the bridge. Hand launching and catching can be helpful. All is happening here is that the AC compass is influenced by the bridge and senses the change when it moves away from it.

 

[Meta4]

First time I did not get GPS lock and had calibrate compass. Today I tried again. I had GPS but the compass warning again. Lifted off the ground and the bird went nuts. Almost impossible to control. Just going every which way imaginable. I was only at about 20 feet. After a crazy struggle I got it down on the ground.
...
I can't calibrate compass there it fails..

Any time your Phantom brings up the calibrate warning, it's 99% sure that you have placed the Phantom somewhere close to a lot of iron or steel or electrical cables.
Your compass is telling you that it has detected a magnetic field that's significantly different from the earth's normal field - you are close to a bunch of steel etc.
You should never calibrate the compass in that sort of environment and you should never launch from there.
The correct thing to do whenever you see that message is to move away from the source of the magnetic interference.

Here's a technical explanation of what the problem is with launching from a steel surface:
Looking for Trouble ??

 

[ianwood]

If you are flying on or near structures made of metal, do yourself a favor and check the compass value before taking off. And if it's bad or you get prompted to calibrate compass, DO NOT CALIBRATE it! You need to find a different spot to take off.

 

[bkushner]

This sounds like what happened to me at the same location on two separate days I was in GPS at launch then right after take-off I received 4 error messages and the copter went into Atti mode the alarms were goin off pop-ups the first time it happened once I got about 100 ft away from the launch point it went back into GPS and I flew a normal flight and landed without issue , I just dont launch at that spot no more the risk ain't worth it .
Here's a pic of the object on the pier of what I believe cause it. A sundial.View attachment 86337

Was the drone out of control? That's what made me panic. As soon as I lifted off the drone started to take off on it's own. I panicked and brought it back. Went into ATTI mode no different, bird wanted to take off on it's own.

 

[bkushner]

Calibrating the compass at your launch point in these circumstances is ill advised. You would likely have found that had you stuck to your existing calibration all would have been good once you were in the air clear of the bridge. Hand launching and catching can be helpful. All is happening here is that the AC compass is influenced by the bridge and senses the change when it moves away from it.

I didn't try to calibrate compass 2nd time. I lifted off and the drone took off on it's own, I panicked and brought it back. Are you saying what I suspected is right, I should have just let it go until it cleared the bridge and it would have corrected it's self?

 

[bkushner]

If you are flying on or near structures made of metal, do yourself a favor and check the compass value before taking off. And if it's bad or you get prompted to calibrate compass, DO NOT CALIBRATE it! You need to find a different spot to take off.

Yeah the area to fly from is all the same on the bridge..no where to move to.

 

[With The Birds]

I didn't try to calibrate compass 2nd time. I lifted off and the drone took off on it's own, I panicked and brought it back. Are you saying what I suspected is right, I should have just let it go until it cleared the bridge and it would have corrected it's self?

If you had a calibration from elsewhere it should have been fine once you were ckear of the bridge. You may have needed to land in ATTI mode however and in some instances the heading will be off when you are close in and you have to temporarily reassign the sticks. I had one occasion wher straight ahead on the elevator caused the AC to fly almost straight backwards.

 

[bkushner]

If you had a calibration from elsewhere it should have been fine once you were ckear of the bridge. You may have needed to land in ATTI mode however and in some instances the heading will be off when you are close in and you have to temporarily reassign the sticks. I had one occasion wher straight ahead on the elevator caused the AC to fly almost straight backwards.

A thought comes to mind. What if you did a RTH would the aircraft land itself as usual or no?

 

[With The Birds]

A thought comes to mind. What if you did a RTH would the aircraft land itself as usual or no?

RTH needs sufficient satellites in view to determine a Location fix and valid heading data from the compass. It wouldn't fly far into the area of magnetic disturbance before an anomaly was detected and ATTI mode entered (as always seems to be the case when compass and GPS don't correlate as expected).

 

[shockwave199]

I had the same behavior taking off from a concrete sidewalk which I'm sure was laced with rebar. This was with a P3 but the same thing happened - a complete dump out to atti mode and major compass error. Like you, I wasn't high or far away but it was windy enough to make it a challenge to land. Doesn't the p4p have two compasses? In any case, don't take off there again. Asking for major trouble.

 

[neven]

Calibration should always be done in non-metal enviroment. Check Sensor status in App before takeoff to see if there is possibility of compass error. Some compass errors and ATTI mid-flight are scary AF. If you are taking off from location like that you can avoid them if you have someone holding a drone above his head and then power on and take off. Be extra carefull when landing.

 

[Meta4]

I had the same behavior taking off from a concrete sidewalk which I'm sure was laced with rebar. This was with a P3 but the same thing happened - a complete dump out to atti mode and major compass error. Like you, I wasn't high or far away but it was windy enough to make it a challenge to land. Doesn't the p4p have two compasses? In any case, don't take off there again. Asking for major trouble.

Two compasses doesn't help when both have been screwed up by launching from on top of steel.
See the link in post #5 to see what that does to your Phantom.

 

[lickitysplit11111]

Was the drone out of control? That's what made me panic. As soon as I lifted off the drone started to take off on it's own. I panicked and brought it back. Went into ATTI mode no different, bird wanted to take off on it's own.

Yeah it went totally bonkers on me I had to counter what it wanted to do which only lasted 5-10 seconds but felt longer because of the surprise Atti mode on a windy pier with a drone that has a mind of its own is a recipe for disaster...
Take a peek at your flight records and see what they say, mine had a total of 4 errors ,speed,yaw,compass, and I forget the other maybe magnetic interference ..

 

[bkushner]

Yeah it went totally bonkers on me I had to counter what it wanted to do which only lasted 5-10 seconds but felt longer because of the surprise Atti mode on a windy pier with a drone that has a mind of its own is a recipe for disaster...
Take a peek at your flight records and see what they say, mine had a total of 4 errors ,speed,yaw,compass, and I forget the other maybe magnetic interference ..

I looked at my records and there are NO ERRORS at first but in the midst of fighting to get the drone back the cable came undone from the controller so I lost most of the record as I fought to gain control of the drone.

 

[Calsun]

Interesting problem as many commercial applications involve inspections of towers and buildings and other structures (like a bridge) where magnetic interference is probable. The more accurate the compass the more vulnerable it will be to such interference and the more important to have a way to turn it off completely for a flight and using a different means to control its orientation.

 

[Meta4]

Interesting problem as many commercial applications involve inspections of towers and buildings and other structures (like a bridge) where magnetic interference is probable. The more accurate the compass the more vulnerable it will be to such interference and the more important to have a way to turn it off completely for a flight and using a different means to control its orientation.

You have to be very close to large steel objects to cause problems.
It's impossible to fly without the compass.

 

[KevMo Photog]

Anytime I am on concrete of any kind I am always thinking possible issue. I always use my Case Club Case to take off on top of and have not had any issues with metal or Rebar. Just enough of an insulator to get you off the metal. Parking garages are notorious for Rebar in the pavement.