A directed beam emitter system for robot navigation in which a light beam emitter emits a modulated directed light beam of a first modulation and an omnidirectional diffuse light region emitter emits a modulated diffuse light region of a second modulation. The modulated directed light beam and the modulated diffuse light region overlap in a plane parallel to ground level such that a light beam receiver on a robot may detect either one or both of the modulated directed light beam and the modulated diffuse light region. The light beam emitter is responsive to a control system used to control one or more light beam emitters.