Fixing DJI's Compass Problem

[Pazz]

The following Official DJI NAZA Manual details how to calibrate and solve the drifting and TBE.http://team-blacksheep.freshdesk.com/he ... s/12145075
Page 11, details compass calibration.
Page 29, fixing the TBE.
PDF
NAZA-M_Quick_Start_Guide_v1.20_en.pdf
1.2 MB
This problem is across all DJI NAZA auto pilot systems & all air frames. Solution is to rotate gps module, but how do you do that with phantoms. Also as pointed out by many other rc forums, we are only dealing with a hobby level system. Get what you pay for.[/quote]

I

really think that you need to read up on the background to this issue, as detailed here and in several other threads, before posting further. The points that you are raising have all been beaten to death previously, and it's not very helpful to start all over again from scratch with this discussion.

[/quote]
Sorry you feel that way. I have read the threads & GPS rotation has not really been examined. If you read other threads of different airframe users (here & on other forums) these issues are being looked at differently. The problem with the phantom is that the GPS unit is glued in under the top of the shell, so no one is prepared to pull it apart & see whether it works( love to hear if anyone has). Easier on other airframes where GPS unit is external & adjustable.Just looking for a software fix may not be the answer.[/quote]

 

[xtonex]

other naza != phantom naza's. rotating gps will do nothing for you but rotating a gps puck that has the compass inside will do the same as rotating the phantoms compass on its leg. the difference being in other naza's you can tell the system you rotated the COMPASS. The phantoms compass orientation is hardcoded and cant be adjusted so this is why when the learning/corrections happen after you rotate the phantom compass you just end up with tbe and hooks to the opposite side of what the person was originally experiencing.

 

[Pazz]

other naza != phantom naza's. rotating gps will do nothing for you but rotating a gps puck that has the compass inside will do the same as rotating the phantoms compass on its leg. the difference being in other naza's you can tell the system you rotated the COMPASS. The phantoms compass orientation is hardcoded and cant be adjusted so this is why when the learning/corrections happen after you rotate the phantom compass you just end up with tbe and hooks to the opposite side of what the person was originally experiencing.

So that means a software fix will not work????

 

[xtonex]

other naza != phantom naza's. rotating gps will do nothing for you but rotating a gps puck that has the compass inside will do the same as rotating the phantoms compass on its leg. the difference being in other naza's you can tell the system you rotated the COMPASS. The phantoms compass orientation is hardcoded and cant be adjusted so this is why when the learning/corrections happen after you rotate the phantom compass you just end up with tbe and hooks to the opposite side of what the person was originally experiencing.

So that means a software fix will not work????

Yes and DJI is working on said software fix...

 

[Pazz]

other naza != phantom naza's. rotating gps will do nothing for you but rotating a gps puck that has the compass inside will do the same as rotating the phantoms compass on its leg. the difference being in other naza's you can tell the system you rotated the COMPASS. The phantoms compass orientation is hardcoded and cant be adjusted so this is why when the learning/corrections happen after you rotate the phantom compass you just end up with tbe and hooks to the opposite side of what the person was originally experiencing.

So that means a software fix will not work????

Yes and DJI is working on said software fix...

How do you know the compass orientation is hardcoded in?.Or do you mean hard wired in? Serious question

 

[riblit]

He means its orientation is coded into the firmware.

If you have a look at other flight controllers such as APM, there is a field where you can enter the local magnetic declination. The firmware uses this to convert the magnetic north direction as pointed to by the compass to the true north position as used by the GPS system. The NAZA FC doesn't have this and they have opted to, in some of their controllers, rotate the compass to the magnetic declination in order that it points to true north. The phantom doesn't have this facility as it's compass isn't designed to be rotated.

This is the same as adding or subtracting the local magnetic declination when reading a ( paper ) map when you convert the bearing from your compass to one you can plot on the map.

 

[ianwood]

Pazz, you need to read the thread. Everything you're talking about has been discussed, debated and answered. Several times. Start with the first post which summarizes most all of it.

 

[Pazz]

Pazz, you need to read the thread. Everything you're talking about has been discussed, debated and answered. Several times. Start with the first post which summarizes most all of it.

With all due respect, I reviewed all the posts & can not find the gps unit position has been debated/ resolved. The premise of this thread started with the presumption it is a compass problem & has not considered any real options.

 

[ianwood]

With all due respect, I reviewed all the posts & can not find the gps unit position has been debated/ resolved. The premise of this thread started with the presumption it is a compass problem & has not considered any real options.

OK. Well, it has been brought up several times in this thread. Maybe 6 times. Key thing to know is that unlike the GPS puck on other Naza units, the GPS unit in the Phantom doesn't have any compass in it and therefore has no notion of orientation whatsoever.

 

[N017RW]

Doono said:
"That's why I asked I'm in SE Aust. and my magnetic declination is +12. Paz may actually be referring to his deviation (as he posted). Correctly explained by droneranger."


So Doono, I asked earlier how to measure this DEVIATION so as to understand where his "Mag dev 22 deg." comes from.
One person, Dadcat, posted a link to look up DECLINATION. :roll:

It seems many use the two terms (Dec / Dev) to mean the same thing.
Thus, one must be ware of the context and that not everyone speaks [at] the same level of technical accuracy.

None the less, Declination is expressed as a difference of one system compared to another with both magnitude and polarity.
Difference is synonymous with Deviation.

 

[ianwood]

Deviation and declination should not be confused. They are indeed different. Pretty sure that's even a test question of the FAA's PPL written exam.

 

[xtonex]

Compasses are used to determine the direction of true North. However, the compass reading must be corrected for two effects. The first is magnetic declination, the angular difference between magnetic North (the local direction of the Earth's magnetic field) and true North. The second is magnetic deviation, the angular difference between magnetic North and the compass needle due to nearby sources of iron.

 

[N017RW]

No s#!t Ian!

I'm pointing put that not everyone may be as "up on things" as you or droneranger or whoever.

Due to context, grammar, tense, language, age, education, etc. differences, sometimes you have tor read between the lines and make the proper association yourself.

 

[sar104]

Sorry you feel that way. I have read the threads & GPS rotation has not really been examined. If you read other threads of different airframe users (here & on other forums) these issues are being looked out differently. The problem with the phantom is that the GPS unit is glued in under the top of the shell, so no one is prepared to put in apart & see whether is works. Easier on other airframes where GPS unit is external & adjustable.Just looking for a software fix may not be the answer.

No, it's clear that you have not read the thread, because this has been discussed. It's trivially obvious that this is not the issue - since the Phantom GPS unit does not contain the compass module it is totally orientation-independent, and there is absolutely no point in rotating it.

 

[Navman]

Is Phantom's Learning process a function of Time, Distance or maybe Both?

In John Shaw's telling video he travels considerable distance out & back.

Near Portland Oregon at +16 declination I'm using about 40% of each battery before it settles down.

But I've been staying close to lift off point.

Could we shorten the Learning time by flying as John did, out a distance & back?

 

[badbrad97]

It's not the GPS system Pazz, it's the magnetic declination. That's why it's only seen in areas of high magnetic declination. I'm now flying the beta firmware and can tell you the TBE is almost completely gone and the system is learning faster. There are still some problems with course lock to be sorted. If it was the GPS system it would be there irrespective of magnetic declination.

Any idea when beta 3.05 will be released?

 

[xtonex]

It's not the GPS system Pazz, it's the magnetic declination. That's why it's only seen in areas of high magnetic declination. I'm now flying the beta firmware and can tell you the TBE is almost completely gone and the system is learning faster. There are still some problems with course lock to be sorted. If it was the GPS system it would be there irrespective of magnetic declination.

Any idea when beta 3.05 will be released?

I would assume never since they've spoke of another beta firm coming to the beta teaters soon

 

[Dalite]

A question to the beta testers..... Are you flying 100% ATTI in your tests? So far, that seems to be the only way to isolate the compass data from the GPS Data cable where it is presented to the NAZA. I don't see a NAZA input for compass only data.

 

[John Shaw]

I do use NAZA
All of my testing with 3.05 has been done in GPS Mode (right switch up). I use both IOC off and in Course Lock (left switch).

 

[lucid111]

I am affected too as when I fly FPV straight line on a street it veers to the left at all times.