A localization and obstacle detection system includes a first signal projector configured to project a first signal into an environment and a robot configured to move in the environment. The robot includes a second signal projector configured to project a second signal into the environment; a signal receiver configured to receive the first signal and the second signal; a localizer configured to determine a location of the robot in the environment based at least in part on the received first signal; and a detector configured to determine the presence of an obstacle in the environment based at least in part on the intensity and bearing of the received second signal and without touching the obstacle; wherein the second signal is distinct from the first signal in at least one characteristic.