In this paper, we describe a method for navigation and localization of a mobile robot using sonar sensors in an indoor environment. This is an enhanced version of our previous method (2001) which assumed a perfectly known environment and perfect sensor data. We remove these assumptions by computing a roadmap and selecting geometric features of the environment for localization that are robust in terms of known sensor limitations and uncertainty. In particular, our roadmap-based navigator and localizer have been redesigned to work cooperatively. To identify geometric features, a simple sensor data filter is designed. We present simulation and hardware experiments for a robot equipped with inexpensive sonar sensors in a real environment.