Abstract: A robot lawnmower includes a body and a drive system carried by the body and configured to maneuver the robot across a lawn. The robot also includes a grass cutter and a swath edge detector, both carried by the body. The swath edge detector is configured to detect a swath edge between cut and uncut grass while the drive system maneuvers the robot across the lawn while following a detected swath edge. The swath edge detector includes a calibrator that monitors uncut grass for calibration of the swath edge detector. In some examples, the calibrator comprises a second swath edge detector.

Abstract: An autonomous coverage robot system includes an active boundary responder comprising a wire powered with a modulated current placed along a perimeter of a property, at least one passive boundary responder placed on a property interior circumscribed by the active boundary responder, and an autonomous coverage robot. The robot includes a drive system carried by a body and configured to maneuver the robot across the property interior. The robot includes a signal emitter emitting a signal, where the passive boundary responder is responsive to the signal and a boundary responder detection system carried by the body. The boundary responder detector is configured to redirect the robot both in response to the responder detection system detecting an active boundary responder and in response to detecting a passive boundary responder.