1. An autonomous mobile robot system for sensor-based and map-based navigation in a pipe network based on classification of landmarks, said system comprising: a vehicle for moving through the pipe network; a storage device for storing a topological map of landmarks; a planner for determining in advance an original path plan through the pipe network from a starting point to a destination point of said topological map; a motor for moving said vehicle in the pipe network according to said path plan; a tilt controller for controlling the tilt of said vehicle along its axis of motion and for controlling the position of the vehicle within the pipe of the pipe network at a pipe bottom; a sensor for sensing said vehicle's environment such that the sensor is capable of detecting the presence of the landmark that the vehicle passes while navigating through the pipe network; a classifier for classifying, said detected landmarks sensed by the sensor in terms of a defined landmark classes; a sequence generator for generating a sequence of landmark classes associated with the corresponding landmarks to be encountered while following said original path plan through the pipe network; an estimator for determining a currently plausible position of said vehicle with respect to the topological map based on the expected landmarks and on the classes of the detected landmarks recently passed; a trigger for triggering at least one additional reading of the sensor for detecting any landmark if the estimator cannot determine the currently plausible position in the pipe network according to currently available data on the expected landmarks and on the classes of the passed landmarks, and an updater for updating said path plan if said currently plausible position differs from an expected position expected according to the original path plan of the planner.