Magnetometers and compass directions.

While setting up the Quads for my customers, I often wonder about the following (Jason, I think this my be yours).. ;-)


1. When you look at the dials in the planner, the heading is shown. Is that Heading supposed to be magnetic, or true north based?  When I put a compass next to the quad, must the dials correspond to the compass, or must it differ by the local declination amount?


2. I remember from before the screen where u set up the magnetic declination, a dialogue box appeared where it said " enter the MagDec, -15 to +15" ore something close to that.  By my calculations the MagDec figure for Cape Town, South Africa is -24.5.


2a. Is this correct?

2b. Can you confirm that the porgram will accept that value , less than -15?





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  • GPS nav will be True North.

    I would assume that the setup of the mag should offset it to display TN.

    Wessie, from my military days, half a lifetime away, Mag to Grid, you rid, Grid to Mag, you add. This would be for a Westerly declination.

    Checked that today with my watch, and the sun.

    What I do is to use cli to FIRST cal the offsets, then set -24.5 under declination.

    Set the compass I gave you to + 24.5 degrees, yes, +.

    Then align the compass with the front/aft axis of the aircraft.

    Turn the aircraft so that the needle now is on North on the dial.

    Go to the "Configuration" tab, play with the mag setting, until the screen compass in "Flight Data" shows North .

  • Developer

    Hi Wessie, 

    Try loading up Arduino and connecting via the CLI. I am absolutely sure the declination will accept and float value there. You can double check that the planner is working correctly by doing the same and comparing values. If not, please add it to the issues list at and put Mission planner in the subject line so Michael can see it.

    I can't say for sure your declination is accurate, it can vary quite a bit, even locally.



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