This post is a continuation with my unhealthy obsession with why the compass API on Windows Phone 7 doesn't actually point north.
I captured the following data rotating my Nokia Lumia 800 a full 360 degrees. Admittedly the rotation by hand so there is a fair bit of noise in the readings.
What it does show is:
- the Magnetic Heading drastically changing when it reaches 256°
- the declination changing from -129° to +127°
Magnetic versus True Heading
![Windows Phone 7 Magnetic versus True Bearing](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOF4hqIUrPHHyGOe73W5PQklKa6pyK-RLmPLftZ_xRZzjx6X8011ikxTUtGtsQ_lvdsf1CEudLidTLtck_BVmKPTgujo0Bnzkik2sejGTTwxL4w5zF3Awnh0g4L_RcenvYieB04kHMWejd/s1600/DataGraph.png)
Scatter plot of magnetometer readings
Magnetometer Axis Readings by Bearing rotation - radar
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlHQVrEDdr7zTQXvEdJfBPC4a2BcGtZITs_2CBZcei0uSKJ9g7Cl1PwfKRxka9t0f4hQrNaC1mIberWogirwNE7XF4GXJWevGqQ-yTSQg-gvzH6UIRdSgro8C4k9Hwd3nAUi8zfCmsSjho/s1600/chart_1+%25282%2529.png)
Magnetometer Axis Readings by Bearing rotation - line
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXH9VBdffHJVNdGXY90ySnCefbw6bdaZuTMQCtvtc5J9KrBU2y9Sfq1WG6noV92CzMvuUEZaq5U1jyaUyjW1s56UA_xRqCGddmNaGJDlox1lZ9LKuAimg2UPzWkmJEHMmf995tuJaCCH4s/s1600/MagnetometerReading.png)
See also: