The telemetry value "Yaw" is different from the read analog compass value

ArduCopter Copter 4.1
1

Hello,
this is my first time posting on the copter forum. I usually post my questions in the “trad helicopter” forum.

I am using a Pixhawk Mini 4 with an external compass/GPS module. I have disabled the internal compass.

I wanted to configure a large scale helicopter using the “Large Vehicle MagCal” method, which caused problems (see here I need your help with "Large Vehicle MagCal").

I noticed that the telemetry value “Yaw” (which is displayed in the MP) differs from my analog compass by about 6 degrees. Unfortunately, I did not get any answers in the “Trad Heli” forum.

Therefore I ask my question here:

Is the telemetry value “Yaw” determined by the GPS signal or by the magnetic compass in the GPS module?

Why does the “Yaw” value deviate from my analog compass by 6 degrees?

I can manipulate the “Yaw” value by entering wrong values in the setup function of the “Large Vehicle MagCal”. Instead of the value “0” read from the analog compass, I enter e.g. “354” degrees, then the “Yaw” value changes from 6 degrees to 359 degrees.

I would be glad to get some explanations from this forum. Thank you very much.

BR

Heri

2

just google for “magnetic declination”
The magnetic north and the geographic north are two different things.

3

@amilcarlucas Thank you for your answer.
Yes, I know, there is a difference between these.

So, shows the value “Yaw” the geographic north? And therefore, comes the value Yaw" from the GPS?
And is this my solution for the difference between my analog compass an the Value “Yaw”?

If so, then my problems with my scale helicopter do not come from an incorrect entry by me in the input field for “Large Vehicle MagCal”?

Because that is the original intention for my questions.
Do I have an input problem or does my problem of a helicopter playing crazy come from some other cause?

Do I have to enter in the input field for “Large Vehicle MagCal” the value from my analog compass, or the one GPS value from a geographic north?

This is exactly my confusion.

BR

Heri