Method of cleaning the bottom of a pool

A method of cleaning a bottom portion of a pool with the aid of a self-propelling, motorized pool cleaner, the pool cleaner travelling to and fro, with parallel movement at change of direction, in straight paths between two opposite walls of the pool while collecting material lying at the bottom of the pool, said pool cleaner comprising drive members governing movement of the pool cleaner and control means arranged to emit control signals to the drive members in order to change the direction of travel when encountering a wall, comprising moving the pool cleaner in a straight path towards one wall, turning the pool cleaner a half turn, and simultaneously displacing the pool cleaner laterally perpendicular to the initial direction of travel, driving the pool cleaner thereafter on a path parallel to the initial direction of travel to the opposite wall of the pool, again turning the pool cleaner a half turn and simultaneously displacing the pool cleaner laterally in the same direction as the lateral displacement at the previous turn, and thereafter moving the pool cleaner back to the opposite wall of the pool, and repeating the process until the bottom portion of the pool has been covered.