An autonomous robot system including a transmitter disposed within a working area and a mobile robot operating within the working area. The transmitter includes an emitter for emitting at least one signal onto a remote surface above the working area. The mobile robot includes a robot body, a drive system configured to maneuver the robot over a surface within the working area, and a navigation system in communication with the drive system. The navigation system includes a receiver responsive to the emitted signal as reflected off of the remote surface and a processor connected to the receiver and configured to determine a relative location of the robot within the working area in response to the receiver responding to the reflected signal.