1. A method of localizing a mobile robot, the method comprising: receiving sensor data of a scene about the robot, the sensor data comprising a three-dimensional point cloud; executing a particle filter having a set of particles, each particle having an associated variance occupancy grid map and a robot location hypothesis; accumulating cloud points in cells of the variance occupancy grid map based on first and second coordinates of the cloud points, each cell accumulating a height variance based on a third coordinate of the accumulated cloud points; updating the variance occupancy grid map associated with each particle based on the received sensor data; assessing a weight for each particle based on the received sensor data; selecting at least one particle based on its weight; and determining a location of the robot based on the at least one selected particle.