title: Forward and backward movement detection with IMU
body: <p>We have an embedded device mounted in a vehicle. It has accelerometer, gyrosopce and GPS sensors on board. The goal is to distinguish when vehicle is moving forward and backward (in reverse gear). Sensor's axis are aligned with vehicle's axis.
  Here's our observations:</p>
  
  <ul>
  <li>It's not enough to check direction of acceleration, because going backwards and braking while moving forward would show results in the same direction.</li>
  <li>We could say that if GPS speed decreased 70 -> 60 km/h it was a braking event. But it becomes tricky when speed is &lt; 20 km/h. Decrease 20 -> 10 km/h is possible when going both directions.</li>
  <li>We can't rely on GPS angle at low speeds.</li>
  </ul>
  
  <p>How could we approach this problem? Any ideas, articles or researches would be helpful.</p>