title: Compare device 3D orientation with the sun position
body: <p>I am working on an app that requires the user to aim his iPhone to the sun in order to trigger a special event.</p>
  
  <p>I can retrieve the device 3D orientation quaternion based on the gyroscope and CoreMotion framework, from this I can get the yaw, roll and pitch angles.
  I can also compute the sun's azimuth and zenith angle based on the current date and time (GMT) and the latitude and longitude.
  What I am trying to figure out next is how to compare these two sets of values (phone orientation and sun position) to accurately detect the alignment of the device with the sun.</p>
  
  <p>Any ideas on how to achieve that?</p>