Robotic mower and a method for navigating the robotic mower

A robotic mower (2) for performing navigating within a work area (4), wherein the work area (4) is limited by a boundary (6), the robotic mower (2) comprising a satellite-based positioning receiver, a dead reckoning sensor (10), a controller (12) comprising a processor (14) and a memory (16), the memory (16) comprising instructions which when executed by the processer (14) causes the mower to:

• repeatedly determine a position of the robotic mower (2) the satellite-based positioning receiver comprising at least one of a Real-Time Kinematic (RTK) receiver, a Global Positioning System (GPS) receiver, or a Differential Global Navigation Satellite System (DGNSS) receiver,
• navigate the robotic mower (2) within the work area (4) based on the determined position,
• determine that a new position of the robotic mower (2) cannot be accurately obtained,
• determine a position uncertainty distance (R) based on the positions obtained by the satellite-based positioning receiver and the dead reckoning sensor (10),
• generate a trajectory (X) of the positions (pp1 . . . n) determined by the satellite-based positioning receiver while the robotic mower (2) navigates,
• generate a trajectory (Y) of the positions (pd1 . . . n) determined by the dead reckoning sensor (10) while the robotic mower (2) navigates,
• align by moving at least one of the generated trajectories (X, Y) within a 2D or 3D coordinate system for minimisation of the distance between the trajectories (X, Y) resulting in aligned trajectories (X, Y′),
• calculate a metric of difference (MOD) between the aligned trajectories (X, Y′) for quantifying the alignment quality of the aligned trajectories (X, Y′),
• determine the position uncertainty distance (R) as the metric of difference (MOD) between the aligned trajectories (X, Y′),
• calculate a distance (D) to the closest boundary (6),
• determine a navigation margin as the difference between the distance (D) to the closest boundary (6) and the position uncertainty distance (R), and
• execute a safety operation if the navigation margin equals a predetermined value.