> For the complete documentation index, see [llms.txt](https://docs.theseus.us/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.theseus.us/cyclops/uav-integration/mounting-your-compass.md).

# Mounting your compass

Cyclops fuses magnetometer data for its heading estimate. An accurate compass reading is critical for correct position updates from Cyclops. Mounting the compass in a location that is far from electromagnetic interference from motors, wires, etc. is extremely important, as even a \~5 degree heading offset can cause position estimates to drift.

For more information on how to calibrate and mount your compass to reduce interference, please read [this page ](https://ardupilot.org/copter/docs/common-magnetic-interference.html)on Magnetic Interference.

Depending on the platform, it may be difficult to mount the compass far from interference. For our testing platforms we mount the compass on the wing so that it is far from interference, seen below:

<figure><img src="https://2060891120-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhzvlBbeiwnrjdGDAaBcQ%2Fuploads%2FMsZiIzzZFGmsQwkTMZd6%2Fwing_compass%20(1).png?alt=media&amp;token=0c35e3ba-b43e-4c01-94d2-818623aa973e" alt=""><figcaption></figcaption></figure>

After mounting your compass, it is best practice to do a test flight and review the ArduPilot logs after. These logs will have data showing the motors interfere with the compass. If interference is high, a [MagFit](https://firmware.ardupilot.org/Tools/WebTools/MAGFit/) could be useful. Read [this page](https://ardupilot.org/copter/docs/common-magfit.html) for information on the MagFit tool.

We provide an extended compass calibration script for calculating the compass extrinsics which can improve compass readings to \~1 deg of error. More information can be found [here](/cyclops/autopilot-integration/ardupilot/fine-tune-magnetometer.md).

{% hint style="info" %}
Extended compass calibration will only be effective if interference is minimal and the error is small.
{% endhint %}