Read original post by Bary Nusz at Falafel Software Blog
In my last post I came up with a simple compass application and how to correct for sensor misalignments. In that application I had a blue arrow that always points up and a yellow arrow that always points North. Now I wanted to add another arrow showing the raw magnetometer readings. For the simple compass application, we just needed to use the Motion Sensor API. To get access to the raw magnetometer readings, we need to use the Compass API to get to the MagnetometerReading property.