A computer-implemented medical method of automatically determining an orientation of a medical instrument base (206, 303) in relation to a robotic system (200, 300), the method excluding any method of surgery excluded from patentability according to Article 53 (c) EPC, the method comprising the following steps: - acquiring first movement data associated with a movement of the robotic system from an initial to a final position relative to a first reference; wherein the step of acquiring first movement data comprises recording at least an initial position and a final position of the robotic system; - acquiring second movement data associated with a movement of a marker device from an initial to a final position relative to a second reference, wherein the step of acquiring second movement data comprises recording at least an initial position and a final position of the marker device; - wherein the marker device is attached to the medical instrument base, - wherein the medical instrument base is movably attached to the robotic system, - determining a relative movement of the robotic system from its initial to its final position, - determining a relative movement of the medical instrument base from its initial to its final position, - comparing the first and second movement data and determining a comparison result, wherein the step of comparing the first and second movement data comprises comparing the relative movement of the robotic system with the relative movement of the medical instrument base; - using the comparison result for determining the orientation of the medical instrument base in relation to the robotic system, - comparing the first movement data with a robotic minimum threshold regarding the amount of movement of the robotic system and quantifying the first movement data as significant if the comparison reveals that the first movement data are above the minimum threshold, - determining that the first and second movement data are consistent based on at least one predefined consistency criterion, and - determining that the first and second movement data are suitable for the orientation determination. - acquiring first movement data associated with a movement of the robotic system from an initial to a final position relative to a first reference; wherein the step of acquiring first movement data comprises recording at least an initial position and a final position of the robotic system; - acquiring second movement data associated with a movement of a marker device from an initial to a final position relative to a second reference, wherein the step of acquiring second movement data comprises recording at least an initial position and a final position of the marker device; - wherein the marker device is attached to the medical instrument base, - wherein the medical instrument base is movably attached to the robotic system, - determining a relative movement of the robotic system from its initial to its final position, - determining a relative movement of the medical instrument base from its initial to its final position, - comparing the first and second movement data and determining a comparison result, wherein the step of comparing the first and second movement data comprises comparing the relative movement of the robotic system with the relative movement of the medical instrument base; - using the comparison result for determining the orientation of the medical instrument base in relation to the robotic system, - comparing the first movement data with a robotic minimum threshold regarding the amount of movement of the robotic system and quantifying the first movement data as significant if the comparison reveals that the first movement data are above the minimum threshold, - determining that the first and second movement data are consistent based on at least one predefined consistency criterion, and - determining that the first and second movement data are suitable for the orientation determination.