Abstract: An automatic robotic lawn sprinkler providing a water powered, articulated, actuation and control system aiming a continuous stream of water to all coordinates within a polar coordinate system comprising a manually programmable base assembly for anchoring to the ground and containing site specific range data, an azimuth rotor assembly rotatably mounted to the base in a horizontal plane, a range rotor assembly rotatably mounted in a vertical plane substantially perpendicular to the azimuth rotor, an azimuth actuation and control system, range actuation and control system, and a mechanism for variably controlling range rate and flow volume.