A method of performing simultaneous localization of a mobile body and mapping of its environment, the method comprising the following steps, carried out by a data processor: a) defining: - an occupancy grid on a region of said environment, the grid comprising a plurality of cells, an occupancy probability by an obstacle being associated to each cell of the occupancy grid, and - a pose grid (Π) comprising a plurality of cells, each representing a position and orientation of the mobile body, a pose probability being associated to each cell of the pose grid; b) receiving a first time series of a plurality of distance measurements (z 1, z 2), each of said measurements being representative of a distance between a point of the mobile body and at least one nearest obstacle and, upon reception of a distance measurement: either b1) updating the occupancy probabilities of the occupancy grid as a function of present values of said occupancy probabilities, of the received distance measurement and of the pose probabilities of the pose grid; or b2) updating the pose probabilities of the pose grid as a function of present values of said pose probabilities, of the received distance measurement and of the occupancy probabilities of the occupancy grid; and c) receiving a second time series of odometry measurements (u 1, u 2), each of said measurements being representative of a motion of the mobile body in the environment and, upon reception of an odometry measurement, updating the pose probabilities of the pose grid as a function of present values of said pose probabilities and of the received odometry measurement; part of the distance measurements being used for carrying out sub-step b2 of updating the pose probabilities of the pose grid and part of the distance measurements being used for carrying out sub-step b1 of updating the occupancy probabilities of the occupancy grid. a) defining: - an occupancy grid on a region of said environment, the grid comprising a plurality of cells, an occupancy probability by an obstacle being associated to each cell of the occupancy grid, and - a pose grid (Π) comprising a plurality of cells, each representing a position and orientation of the mobile body, a pose probability being associated to each cell of the pose grid; - an occupancy grid on a region of said environment, the grid comprising a plurality of cells, an occupancy probability by an obstacle being associated to each cell of the occupancy grid, and - a pose grid (Π) comprising a plurality of cells, each representing a position and orientation of the mobile body, a pose probability being associated to each cell of the pose grid; b) receiving a first time series of a plurality of distance measurements (z 1, z 2), each of said measurements being representative of a distance between a point of the mobile body and at least one nearest obstacle and, upon reception of a distance measurement: either b1) updating the occupancy probabilities of the occupancy grid as a function of present values of said occupancy probabilities, of the received distance measurement and of the pose probabilities of the pose grid; or b2) updating the pose probabilities of the pose grid as a function of present values of said pose probabilities, of the received distance measurement and of the occupancy probabilities of the occupancy grid; and b1) updating the occupancy probabilities of the occupancy grid as a function of present values of said occupancy probabilities, of the received distance measurement and of the pose probabilities of the pose grid; or b2) updating the pose probabilities of the pose grid as a function of present values of said pose probabilities, of the received distance measurement and of the occupancy probabilities of the occupancy grid; and c) receiving a second time series of odometry measurements (u 1, u 2), each of said measurements being representative of a motion of the mobile body in the environment and, upon reception of an odometry measurement, updating the pose probabilities of the pose grid as a function of present values of said pose probabilities and of the received odometry measurement;