A garden-based robotic system including a robot and data storage operable to store data defining the boundary of a working area within the garden, the robot comprising: a payload actuable to perform work on a portion of the garden adjacent the robot; one or more positioning systems (49A, 49B); wherein the robot is programmed to operate in at least the following two modes: (i) a perimeter coverage mode, wherein the robot, using said one or more positioning systems, moves within a perimeter area with said payload active, said perimeter area being defined within the robot's programming such that it is adjacent to and generally follows the path of said boundary; (ii) an internal area coverage mode, wherein the robot, using said one or more positioning systems (49A, 49B) and said data defining the boundary of the working area, moves within an interior area with said payload active, said interior area being defined within the robot's programming such that it is generally located within said perimeter area; wherein the accuracy of said one or more positioning systems (49A, 49B) is greater during said perimeter coverage mode than during said internal area coverage mode; characterised in that: said interior area and said perimeter area are further defined within the robot's programming such that the interior area approaches to or overlaps with said perimeter area sufficiently to substantially avoid gaps between the area that is in practice covered by said payload during said internal area coverage mode, taking into account the accuracy of said one or more positioning systems (49A, 49B) during said internal area coverage mode, and the area that is in practice covered by said payload during said perimeter coverage mode, taking into account the accuracy of said one or more positioning systems (49A, 49B) during said perimeter coverage mode; and said interior area is further defined within the robot's programming to be sufficiently distant from the boundary of the working area to substantially avoid the robot in practice moving beyond the boundary during said internal area coverage mode, taking into account the accuracy of said one or more positioning systems (49A, 49B) during said internal area coverage mode. a payload actuable to perform work on a portion of the garden adjacent the robot; one or more positioning systems (49A, 49B); wherein the robot is programmed to operate in at least the following two modes: (i) a perimeter coverage mode, wherein the robot, using said one or more positioning systems, moves within a perimeter area with said payload active, said perimeter area being defined within the robot's programming such that it is adjacent to and generally follows the path of said boundary; (ii) an internal area coverage mode, wherein the robot, using said one or more positioning systems (49A, 49B) and said data defining the boundary of the working area, moves within an interior area with said payload active, said interior area being defined within the robot's programming such that it is generally located within said perimeter area; (i) a perimeter coverage mode, wherein the robot, using said one or more positioning systems, moves within a perimeter area with said payload active, said perimeter area being defined within the robot's programming such that it is adjacent to and generally follows the path of said boundary; (ii) an internal area coverage mode, wherein the robot, using said one or more positioning systems (49A, 49B) and said data defining the boundary of the working area, moves within an interior area with said payload active, said interior area being defined within the robot's programming such that it is generally located within said perimeter area; wherein the accuracy of said one or more positioning systems (49A, 49B) is greater during said perimeter coverage mode than during said internal area coverage mode; said interior area and said perimeter area are further defined within the robot's programming such that the interior area approaches to or overlaps with said perimeter area sufficiently to substantially avoid gaps between the area that is in practice covered by said payload during said internal area coverage mode, taking into account the accuracy of said one or more positioning systems (49A, 49B) during said internal area coverage mode, and the area that is in practice covered by said payload during said perimeter coverage mode, taking into account the accuracy of said one or more positioning systems (49A, 49B) during said perimeter coverage mode; and said interior area is further defined within the robot's programming to be sufficiently distant from the boundary of the working area to substantially avoid the robot in practice moving beyond the boundary during said internal area coverage mode, taking into account the accuracy of said one or more positioning systems (49A, 49B) during said internal area coverage mode.