A robotic work tool system for defining a working area in which a robotic work tool is subsequently intended to operate, the robotic work tool system comprising: a robotic work tool comprising at least one sensor unit configured to collect sensed input data, wherein the at least one sensor unit is configured to collect the sensed input data while the robotic work tool is driven at least a portion of a lap around the working area to preliminarily define a perimeter around the working area; at least one controller configured to establish a preliminary working area perimeter; and at least one memory configured to store a perimeter adjustment function and further including instructions that, when executed by the at least one controller, cause the at least one controller to adjust the perimeter of the working area by applying the stored perimeter adjustment function to the established preliminary working area perimeter and thereby produce an adjusted working area perimeter, wherein the perimeter adjustment function is based on the collected sensed input data and wherein the sensed input data corresponds to terrain features, characterized in that the at least one sensor unit comprises an imaging device and wherein the at least one memory further includes instructions that, when executed by the at least one controller, cause the at least one controller to: detect one or more terrain feature edges in the working area, wherein the collected sensed input data comprises imaging data and wherein the one or more edges are detected based on processing of the imaging data; and align the preliminary working area perimeter in parallel with the one or more terrain feature edges by applying the stored perimeter adjustment function to the established preliminary working area perimeter and thereby produce the adjusted working area perimeter. a robotic work tool comprising at least one sensor unit configured to collect sensed input data, wherein the at least one sensor unit is configured to collect the sensed input data while the robotic work tool is driven at least a portion of a lap around the working area to preliminarily define a perimeter around the working area; at least one controller configured to establish a preliminary working area perimeter; and at least one memory configured to store a perimeter adjustment function and further including instructions that, when executed by the at least one controller, cause the at least one controller to adjust the perimeter of the working area by applying the stored perimeter adjustment function to the established preliminary working area perimeter and thereby produce an adjusted working area perimeter, wherein the perimeter adjustment function is based on the collected sensed input data and wherein the sensed input data corresponds to terrain features, characterized in that the at least one sensor unit comprises an imaging device and wherein the at least one memory further includes instructions that, when executed by the at least one controller, cause the at least one controller to: detect one or more terrain feature edges in the working area, wherein the collected sensed input data comprises imaging data and wherein the one or more edges are detected based on processing of the imaging data; and align the preliminary working area perimeter in parallel with the one or more terrain feature edges by applying the stored perimeter adjustment function to the established preliminary working area perimeter and thereby produce the adjusted working area perimeter. detect one or more terrain feature edges in the working area, wherein the collected sensed input data comprises imaging data and wherein the one or more edges are detected based on processing of the imaging data; and align the preliminary working area perimeter in parallel with the one or more terrain feature edges by applying the stored perimeter adjustment function to the established preliminary working area perimeter and thereby produce the adjusted working area perimeter.