title: iPhone - What does the gyroscope measures? Can I get an absolute degree measurement in all axis?
body: <p>I am relatively new to iPhone development and I am playing with the gyroscope, using Core Motion. After a few tests, this is my question.</p>
  
  <p>What information is exactly the gyroscope measuring? absolute angles? I mean, suppose I hold my phone in portrait, at exactly 90 degrees and start sampling. These may be not the correct values, but suppose that at this position, the gyroscope gives me 0, 0 and 0 degrees for yaw, pitch and roll.</p>
  
  <p>Now I throw my iphone in the air and as it goes up it rolls at random a high number of full turns in all axis and returns to my hand at the same position as before. Will the gyroscope read 0,0,0 (meaning that it has the same position as before = absolute angle) or not? </p>
  
  <p>If not, there's a way to measure absolute degrees in all axis? As absolute degrees I mean assuming 0,0,0 as the position it was when the sampling started.</p>
  
  <p>thanks</p>