A robot must perform localization, that is, it must know its own position in the environment. It can compute its position relative to landmarks whose position is known using the techniques of classical land surveying. Accurate localization can be achieved using the satellite-based global positioning system (GPS). Probabilistic localization is used in environments where GPS cannot be used, for example, inside a building. Given a map of the environment the robot computes its most likely location based upon data from its sensors. The probabilistic computations can handle uncertainty in the sensors and in the motion of the robot.