“…As shown in Figure A, the local gridmap contains noisy data owing to the multipath effect of sonar sensors, which need to be suppressed in order to acquire navigable areas in a reliable manner. To do this, a sonar sensor measurement is modeled to evaluate the grid confidence of each occupied grid cell :where s indicates a sensor measurement, S occ ( i , j ) is a set of sensor measurements that determine whether grid cell ( i , j ) is occupied, and P s is the sound pressure of a sonar sensor measurement . The grid confidence assesses the reliability of each occupied grid cell, as shown in Figure B.…”