This paper describes an autonomous, wearable location awareness system that determines a user's location within a building given a map of that building. The system uses a moderate number of ultrasonic range transceivers as the sensing elements. Given a set of range readings from these sensors, the system attempts to match those actual readings to expected readings associated with a set of candidate locations for the wearer. These expected readings are calculated using a simulation model of the propagation of ultrasonic signals within a building. A complementary algorithm is given for determining the wearer's movement between rooms, allowing for the uncertainty associated with sensor readings in complex, multiroom environments. A wearable prototype system is described and results from this system in a range of scenarios are presented and analyzed