Hi Guys , 

I've been using the APM 2.6 (No internal compass) with the NEO-M8N GPS+Compass via I2C. My compass directions are very inconsistent. I've done calibration several times but the direction is wrong. 

When I point north -> Heading shows north - 15 degrees

When I point south -> Heading shows south - 15 degrees

When I point East   -> Heading shows east but drifts until it shows South

You can see it in the attached YouTube video - https://www.youtube.com/watch?v=sD5MoYczz4g

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Assuming your APM and GPS are both pointing in the same direction my guess is your compass+GPS orientation is incorrect.

MP defaults to an orientation of 180 degrees which may not be correct for your particular module.

I had similar issues with an M8N and resolved them by selecting: ROTATION_ROLL_180_YAW_270

You can also try entering your declination manually.

Thank you, could you send me a picture of the forward facing direction for the orientation of roll 180, yaw 270? It'd be very helpful!

No need for a photo as you don't physically roll or yaw your GPS+compass module. The settings have to do with how the unit was assembled (assuming the module is pointing north). 

Start with the module mounted normally -- GPS antenna facing up and the arrow pointing north -- then try different orientations in the drop-down list.  Select an option, then return to the Flight Data screen to see what difference you made.

You'll know you have it right when you can rotate your plane and both the GPS and compass point north and rotate in the same direction. If the roll is set incorrectly then as you rotate your craft the GPS and compass will move in opposite directions.

After that you can re-calibrate and you should be good to go.


The reason I ask for a photo is because my m8n didn't come with an arrow :( I was wondering how you positioned yours.

Aha!  If yours was assembled like mine (and it seems to be) then viewed from the top, assume the wires plug into the 'south' end which places 'north' at the opposite end (ie your photo has W at the top, S to the right, and N to the left).

As an aside, you can make your own arrow by waiting until the GPS gets a lock and then seeing which way it points in MP ; )

Thanks Crady you've been super helpful, I got rol_180_yaw_45 work for me. I'll try out a flight today and let you know how it goes. Do you fly a wing too?

Huzzah! That is awesome. Really glad you got it sorted.

I don't currently have any fixed-wing aircraft but I'm planning to do a build in the Fall.

Was your test flight a success?

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