sed in <a href="https://wadpac.github.io/GGIR/articles/chapter1_WhatIsGGIR.html">chapter
1</a>, we favour the approach were we try to use our knowledge of the
sensor. Our knowledge of the sensor tells us the an acceleration signal
comes with three components that need to be separated:</p>
<ol style="list-style-type: decimal">
<li>The acceleration related to the gravitational acceleration. In the
absence of movement the three acceleration signals inform us about the
orientation of the accelerometer relative 