To Those Who've Experienced Compass Errors.....

Im just saying in an environment like that, there is good probability you will encounter compass errors and then PGPS and RTH will not work. Being ready for that just means that, be ready to fly in attitude mode.

What does a phantom do when you attempt RTH during a compass error ? I dont know actually. Hover until the battery drains and then land in place I assume?
 
*Aircraft Model- P3A
* Aircraft Firmware- Latest
*Remote Controller Firmware- Latest
*GO App Version or SDK App Version- Latest android version of DJI app
*Startup Sequence- Tablet, controller, P3A
*Calibration Technique- 360 horizontal turn, then 360 frontside down turn.

These questions may or may not be relevant, but there might be a response from you that clearly stands out as possible cause to a compass issue. Proper calibrations are important.

How fast or slow are you going through the calibration process?

How well do you keep the aircraft level to insure a accurate calibration?

When rotating the aircraft which direction are you turning; CC or CCW?

When completing step 1 the 360 degree stage rotation; what color is the light and is it solid or blinking? (If you are not sure which it is and have to go through the process or look up the answer, be sure to include that info in your response here.)

When setting up the aircraft for step 2 to do the nose down vertical process; do you continue on and complete the process, or do you allow the camera & gimbal to finish resetting before starting step 2?

Once the calibration process is complete; do you continue on and fly, or do you power cycle the aircraft?
 
Do you remember about what time (UTC) you were flying? Maybe there was something up with the sun. My problems occurred about 11:20am aug 1st (UTC). I used to not calibrate after every flight. I started doing so again because sometimes when I try to fly a straight line it wants to yaw to one side or another. It seems it isn't as bad when I calibrate before flight.

I'll see if I can find a place to upload the DAT from the flight then post.
Yes my problems were around the same time and the same problems. They were in affect till about 4:50. But I flew at around at night at 9:30 and took some shots of a storm .
Do you remember about what time (UTC) you were flying? Maybe there was something up with the sun. My problems occurred about 11:20am aug 1st (UTC). I used to not calibrate after every flight. I started doing so again because sometimes when I try to fly a straight line it wants to yaw to one side or another. It seems it isn't as bad when I calibrate before flight.

I'll see if I can find a place to upload the DAT from the flight then post.
Yes I was flying around those times and my compass was affected around 5 or 6 pm But the problems seemed to go away at night. Earlier in the day my phantom wouldn't stay straight either but I had no compass error than later In the day around 2 pm I had the Compass error and the phantom veered to the left. Luckily RTH was still working. I am trying to look at different website for solar activity and try to post a link
 
Im just saying in an environment like that, there is good probability you will encounter compass errors and then PGPS and RTH will not work. Being ready for that just means that, be ready to fly in attitude mode.

What does a phantom do when you attempt RTH during a compass error ? I dont know actually. Hover until the battery drains and then land in place I assume?

I'm on board with what you said in the previous post. I had thought by adding what could happen would be like icing on the cake to what you already mentioned.


What does a phantom do when you attempt RTH during a compass error ? I dont know actually. Hover until the battery drains and then land in place I assume?
Not necessarily. What if GPS is part of the problem and the Aircraft is confused, and then the aircraft takes off after selecting RTH cause it thinks Home Point is 20 miles away?

My point is if a Pilot receives an Compass Error of any kind, they need to know that there NO possibility that Error will fix itself and continue on. The Pilot should switch over to A-Mode asap and get the Aircraft safely back to Home Point right away. If the Pilot has strong to deal with in such a case, then the best action might be to land the Aircraft and go retrieve it.
 
Yes my problems were around the same time and the same problems. They were in affect till about 4:50. But I flew at around at night at 9:30 and took some shots of a storm .

Yes I was flying around those times and my compass was affected around 5 or 6 pm But the problems seemed to go away at night. Earlier in the day my phantom wouldn't stay straight either but I had no compass error than later In the day around 2 pm I had the Compass error and the phantom veered to the left. Luckily RTH was still working. I am trying to look at different website for solar activity and try to post a link

...and you also should go buy a lottery ticket because after receiving a compass error and continuing on with all that flying....you are Lucky! These type of stories usually have a different ending.
 
If RTH is initiated while there is a compass error the P3 will attempt to fly towards home based on the value of Yaw. If Yaw isn't correct then it flies in the wrong direction.

DatCon computes magYaw that is derived from the current values of the magnetometers and then corrected with the current roll and pitch from the FC.

In this flight a compass error had occurred. When the RC connection was lost at time 18 secs the P3 initiated RTH. Yaw had a value of -139 and magYaw had a value of 14. The magYaw value was confirmed to be correct based on the recorded video.The direction of home was about -90 so the P3 turned CW from -140 to -75. That actually turned the P3 from 14 to 58, not in the direction of home.
upload_2016-8-2_9-15-9.png


In this flight the pilot initiated RTH at 71.5 after there had been a compass error. Again, the P3 turned in the direction it thought was home based on Yaw, not the correct value which is indicated by magYaw.
upload_2016-8-2_9-15-28.png
 
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Not necessarily. What if GPS is part of the problem and the Aircraft is confused, and then the aircraft takes off after selecting RTH cause it thinks Home Point is 20 miles away?


Compass error and GPS error are not the same thing. Granite mountains wouldnt impact the GPS, just the compass. And there is no way a GPS fault would put the position off by 20 miles. Or 2 miles for that matter. Either you have a fix or you dont.

My point is if a Pilot receives an Compass Error of any kind, they need to know that there NO possibility that Error will fix itself and continue on.

I disagree. Just climbing a few 100ft may resolve both GPS errors (if caused by obstruction) and compass errors if they are caused by the underground. I can easily prove that too, by flying over a large concrete slab with rebar, nearby where I live. Below ~4m I will have problems, above its fine. Fully reproducible.

I have no idea if the case of the OP climbing higher will actually help, but its the first thing I would try upon getting a compass error near granite mountains or other sources of magnetic interference.
 
Im just saying in an environment like that, there is good probability you will encounter compass errors and then PGPS and RTH will not work. Being ready for that just means that, be ready to fly in attitude mode.
I agree but my phantom did return to home
What does a phantom do when you attempt RTH during a compass error ? I dont know actually. Hover until the battery drains and then land in place I assume?
The phantom properly returned to home and I manually landed inattitude to prevent a fly away. You can still fly the drone but only in attitude which means you loose retur
I'm on board with what you said in the previous post. I had thought by adding what could happen would be like icing on the cake to what you already mentioned.



Not necessarily. What if GPS is part of the problem and the Aircraft is confused, and then the aircraft takes off after selecting RTH cause it thinks Home Point is 20 miles away?

My point is if a Pilot receives an Compass Error of any kind, they need to know that there NO possibility that Error will fix itself and continue on. The Pilot should switch over to A-Mode asap and get the Aircraft safely back to Home Point right away. If the Pilot has strong to deal with in such a case, then the best action might be to land the Aircraft and go retrieve it.
...and you also should go buy a lottery ticket because after receiving a compass error and continuing on with all that flying....you are Lucky! These type of stories usually have a different ending.
Hahaha yes I was luck indeed
 
It blows my mind that the phantom would actually attempt to navigate (home) when it knows, or even thinks, its compass data is invalid. I certainly would never attempt it. Only exception being if it actually used GPS ground track to assess its heading, like a pixhawk can, but we've seen ample evidence that it doesnt do that (or if it tries, fails miserably).
 
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It blows my mind that the phantom would actually attempt to navigate (home) when it knows, or even thinks, its compass data is invalid. I certainly would never attempt it. Only exception being if it actually used GPS ground track to assess its heading, like a pixhawk can, but we've seen ample evidence that it doesnt do that (or if it tries, fails miserably).
Yeah I agree. I had no control over the phantom even tried putting it in attitude mode and all that. I only got signal when it was about 30 meters away. I then proceeded everything manually
 
Compass error and GPS error are not the same thing. Granite mountains wouldnt impact the GPS, just the compass. And there is no way a GPS fault would put the position off by 20 miles. Or 2 miles for that matter. Either you have a fix or you dont.



I disagree. Just climbing a few 100ft may resolve both GPS errors (if caused by obstruction) and compass errors if they are caused by the underground. I can easily prove that too, by flying over a large concrete slab with rebar, nearby where I live. Below ~4m I will have problems, above its fine. Fully reproducible.

I have no idea if the case of the OP climbing higher will actually help, but its the first thing I would try upon getting a compass error near granite mountains or other sources of magnetic interference.

That is what I or most other pro pilots would do that have flown for sometime. But when explaining to the mass newer pilots here which are the majority, and that only have looked at the manual, rather then panic and go into a frenzy they should take a compass error seriously and return to home point.

Btw, I never said compass and gps errors were the same. I did mention if one had taken place and the other also became part of the problem.

(Just sayin.... The P3 does have the ability to try a repair a gps issue. It is setup if it loses gps signal after a set amount of time to start making 360 degree rotations as it is drifting. It will rotate in one direction stop and rotate to the other direction. It will continue doing this until it either receives a gps signal or the battery reaches the critical land point. This happened to me once is how I know. I was lucky and it located a signal before crashing. Once it connected to the signal it climbed to RTH altitude and flew home barely clipping a tree along the way. I actually thought I had lost it and was on the opposite side of my house near the home point mark when I nearly crapped myself when I heard it come past the roof. I was then amazed when watching the video back and seeing what had took place.)
 
If RTH is initiated while there is a compass error the P3 will attempt to fly towards home based on the value of Yaw. If Yaw isn't correct then it flies in the wrong direction.

DatCon computes magYaw that is derived from the current values of the magnetometers and then corrected with the current roll and pitch from the FC.

In this flight a compass error had occurred. When the RC connection was lost at time 18 secs the P3 initiated RTH. Yaw had a value of -139 and magYaw had a value of 14. The magYaw value was confirmed to be correct based on the recorded video.The direction of home was about -90 so the P3 turned CW from -140 to -75. That actually turned the P3 from 14 to 58, not in the direction of home.

So is MagYaw like the x.y.z. of Yaw, or?

Also, are you aware of any kind of tilted compensation in the P3 data, accelerometer?
 
So is MagYaw like the x.y.z. of Yaw, or?

Also, are you aware of any kind of tilted compensation in the P3 data, accelerometer?
magYaw is derived by first computing a vector based on the x, y and z magnetometers. In general, that vector doesn't lie in the xy plane due to the geomagnetic inclination and the roll and pitch of the AC. Using quaternion math that vector is then rotated into the xy plane by using the values of roll and pitch coming from the FC.

magYaw and Yaw will have (close to) the same value unless one of them is incorrect. At batteryOn Yaw gets set to something like magYaw. After that Yaw relies mostly on the IMU sensors (particularly the gyros) and the calculations done by the FC. If the magnetometers are compromised at batteryStart (like launching from a man hole cover) then the incorrect magYaw value will be what initializes Yaw. After launch magYaw becomes correct because the man hole cover is no longer close enough to cause a problem. BUT, Yaw continues to have the incorrect value because while magYaw has been correcting there hasn't been any rotation about the Z axis. This is what happened in the 2 example flights.

Just to be clear magYaw doesn't come from the P3, it comes from a calculation that DatCon does. It's a diagnostic that's useful when the Yaw value is suspect. The P3 may have it's own magYaw look-alike or something similar that's used to detect compass errors.

I didn't understand your second question.
 
Yes my problems were around the same time and the same problems. They were in affect till about 4:50. But I flew at around at night at 9:30 and took some shots of a storm .

Yes I was flying around those times and my compass was affected around 5 or 6 pm But the problems seemed to go away at night. Earlier in the day my phantom wouldn't stay straight either but I had no compass error than later In the day around 2 pm I had the Compass error and the phantom veered to the left. Luckily RTH was still working. I am trying to look at different website for solar activity and try to post a link
Ya, one of the first things I checked when I got home was solar activity and there was nothing unusual. Another poster suggested it might be due to the rock I took off from, which is partly composed of granite, but the problem didn't happen until midway in flight gar away from any terrain. I never really panicked about it, but that abrupt tilt to the Left was a concern for a few seconds.

Sent from my SAMSUNG-SM-N920A using PhantomPilots mobile app
 
magYaw is derived by first computing a vector based on the x, y and z magnetometers. In general, that vector doesn't lie in the xy plane due to the geomagnetic inclination and the roll and pitch of the AC. Using quaternion math that vector is then rotated into the xy plane by using the values of roll and pitch coming from the FC.

magYaw and Yaw will have (close to) the same value unless one of them is incorrect. At batteryOn Yaw gets set to something like magYaw. After that Yaw relies mostly on the IMU sensors (particularly the gyros) and the calculations done by the FC. If the magnetometers are compromised at batteryStart (like launching from a man hole cover) then the incorrect magYaw value will be what initializes Yaw. After launch magYaw becomes correct because the man hole cover is no longer close enough to cause a problem. BUT, Yaw continues to have the incorrect value because while magYaw has been correcting there hasn't been any rotation about the Z axis. This is what happened in the 2 example flights.

Just to be clear magYaw doesn't come from the P3, it comes from a calculation that DatCon does. It's a diagnostic that's useful when the Yaw value is suspect. The P3 may have it's own magYaw look-alike or something similar that's used to detect compass errors.

I didn't understand your second question.

Ok, interesting. So say we're looking a converted .DAT file and on line 1000 we are going to compare the data from that line between Yaw and MagYaw. My question is; what will signify a Good or No Good value reading in the Yaw column?

Something else that comes to mind, I'm going to point something out and I'll need you to tell me if it comes into play or not based on how you have the DatCon setup....

I'm not sure if you are aware of this or not. But let's use line 1000 again for reference. Based on line 1000 if the 1st column(Column A) of data is say Longitude, and if we added another Longitude column at say Column Z(26 columns away from Column A), the readings between the two Longitude columns will be different.

So why they are different is not important in this case. But the point is, they are different. So based on the fact that these two columns are different, my questions is; unless you are using data that comes from columns next to the Yaw Column, the data values are usable. Otherwise data being used from columns with a gap of other columns in between them...could be considered not that accurate.
(I hope you understand what I'm pointing out and asking. Because I don't think I can put it together any other way.)

Btw, at this point scratch the tilted question from earlier.
 
Ok, interesting. So say we're looking a converted .DAT file and on line 1000 we are going to compare the data from that line between Yaw and MagYaw. My question is; what will signify a Good or No Good value reading in the Yaw column?

Something else that comes to mind, I'm going to point something out and I'll need you to tell me if it comes into play or not based on how you have the DatCon setup....

I'm not sure if you are aware of this or not. But let's use line 1000 again for reference. Based on line 1000 if the 1st column(Column A) of data is say Longitude, and if we added another Longitude column at say Column Z(26 columns away from Column A), the readings between the two Longitude columns will be different.

So why they are different is not important in this case. But the point is, they are different. So based on the fact that these two columns are different, my questions is; unless you are using data that comes from columns next to the Yaw Column, the data values are usable. Otherwise data being used from columns with a gap of other columns in between them...could be considered not that accurate.
(I hope you understand what I'm pointing out and asking. Because I don't think I can put it together any other way.)

Btw, at this point scratch the tilted question from earlier.
Sorry but I don't have an answer for you about the Good or No Good value reading in the Yaw column. It's complicated. I'm still trying to figure it out.

On you second question I don't quite get the question, You seem to imply that the ordering of the columns is somehow significant. Is this right? Further, that the distance between two columns somehow affects the accuracy or usefulness of the two columns? I must be missing something. In your example involving two columns labelled Longitude are you saying that the values come from the same source but on the same line have different values?
 
Sorry but I don't have an answer for you about the Good or No Good value reading in the Yaw column. It's complicated. I'm still trying to figure it out.

On you second question I don't quite get the question, You seem to imply that the ordering of the columns is somehow significant. Is this right?

Further, that the distance between two columns somehow affects the accuracy or usefulness of the two columns?

I must be missing something. In your example involving two columns labelled Longitude are you saying that the values come from the same source but on the same line have different values?
Yes. Think of it as a timing situation. As in the position of the aircraft at the time the is able to be collected or written. Or, think of it as a data logger going down the list gathering info.

I used Longitude as an example because the aircraft is likely moving most of the time. Using hspeed might be one to use for the same reason. I just wanted you to know this info because you might want to put certain columns next to each other for a more accurate reading for the diagnostic tools you created.
 
....
Yes. Think of it as a timing situation. As in the position of the aircraft at the time the is able to be collected or written. Or, think of it as a data logger going down the list gathering info.

I used Longitude as an example because the aircraft is likely moving most of the time. Using hspeed might be one to use for the same reason. I just wanted you to know this info because you might want to put certain columns next to each other for a more accurate reading for the diagnostic tools you created.
The ordering of the columns isn't relevant and has no effect on the values or their accuracy. The values in a row all occur at the same time. Every converter that you've seen and any converter you will see works this way
 
Compass errors have recently become a common issue.
100% agreed. I only had 2 flights on a new P3A. Second one is Compass Error. No solution really. Bad product form DJI. They should recall all these drones.
 

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