[Alan Anderson]

The yaw rate "gyro" senses turn rates. To track the absolute angle, you need to know at which angle it starts, integrate the sensor signal to turn rate into position, and account for bias and drift.

For a vertical angle, the dual-axis accelerometer would be more appropriate. If it's stationary or moving at a constant velocity, it measures gravity quite well, and can tell you the angle it is at with respect to "down".

For your application, however, I'd use a potentiometer connected to the tilt mechanism to sense the throw angle directly.