title: Acceleration from device's coordinate system into absolute coordinate system
body: <p>From my Android device I can read an array of linear acceleration values (in the device's coordinate system) and an array of absolute orientation values (in Earth's coordinate system). What I need is to obtain the linear acceleration values in the latter coord. system.</p>
  
  <p>How can I convert them?</p>
  
  <p><strong>EDIT</strong> after Ali's reply in comment:</p>
  
  <p>All right, so if I understand correctly, when I measure the linear acceleration, the position of the phone completely does not matter, because the readings are given in Earth's coordinate system. right?</p>
  
  <p>But I just did a test where I put the phone in different positions and got acceleration in different axes. There are 3 pairs of pictures - the first ones show how I put the device (sorry for my Paint "master skill") and the second ones show readings from data provided by the linear acc. sensor:</p>
  
  <ol>
  <li>device put on left side</li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/blmpu.png" alt="first position">
  <img src="https://i.stack.imgur.com/UBPwF.png" alt="first readings"></p>
  
  <ol start="2">
  <li>device lying on back</li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/IU0AQ.png" alt="second position">
  <img src="https://i.stack.imgur.com/HjLx0.png" alt="second readings"></p>
  
  <ol start="3">
  <li>device standing</li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/7o1sz.png" alt="enter image description here">
  <img src="https://i.stack.imgur.com/M23fC.png" alt="enter image description here"></p>
  
  <p>And now - why in the third case the acceleration occurs along the Z axis (not Y) since the device position doesn't matter?</p>