Method of estimating a position variation of a motion of an apparatus between a first instant and a second instant, said motion including a rotation of the apparatus and said position variation, said position variation including a position and a velocity, wherein estimating said position variation comprises performing a particles filtering for estimating said position and velocity from the probabilistic-weighted average of the particles, said particles filter using a known estimation of said rotation and being parameterized for taking into account a quality of said rotation estimation.