<p>The method involves computing positions and alignments of particles (6) based on previously computed position of an automatic movable apparatus. One of the particles is assumed as a new location of the automatic movable apparatus according to movement of the apparatus with respect to one position depending on measurement results of optical units. The computation of the particles is limited regarding solid angle (alpha) determined by preset moving direction (r) and moving width and/or speed of the apparatus and a spacing region (a).</p>
