Method for ascertaining a closed trajectory by means of a laser and a laser light sensor with a plane measurement field, wherein the measuring field has a coordinate system with an X-coordinate axis and a Y-coordinate axis at right angles to the X-coordinate axis, wherein the laser light sensor is configured to detect on the measurement field the X-coordinate and Y-coordinate of the position of the laser light spot of a laser light beam of the laser striking the measuring field, wherein the method comprises the following steps: arranging the measuring field in a circular cylindrical bore of a body and transferring the measuring field into a first orientation, irradiating the measuring field with a laser light beam produced by the laser and detecting the X-coordinate and the Y-coordinate of the position of the laser light spot of the laser light beam, which the laser light spot adopts on the measuring field, transferring the measuring field successively in time into at least two further orientations, irradiating the measuring field with the laser light beam in each of the further orientations and detecting the X-coordinate and the Y-coordinate of the positions of the laser light spot of the laser light beam, which the laser light spot adopt on the measuring field in each of the further orientations, wherein the X-coordinate axis and the Y-coordinate axis are oriented at right angles to the centre axis of the bore in the first orientation and also in each of the further orientations and the centre of the coordinate system has a predetermined distance from the inner surface of the bore in the direction of the X-coordinate axis or the Y-coordinate axis, wherein the further orientations differ in terms of the magnitude of the orientation angle (φ R) by which the Y-coordinate axis or the X-coordinate axis is inclined in a predetermined sense of rotation in relation to the Y-coordinate axis or the X-coordinate axis of the measuring field in the first orientation, and wherein the measuring field is transferred into the at least two further orientations in step in such a temporal successive fashion that the orientation angle of each of the further orientations is greater than the orientation angle of each orientation adopted earlier in time, wherein, in the orientation adopted last in time, the magnitude of the orientation angle is at least 90 degrees, assigning the orientation angle value of zero degrees to the X-coordinate and Y-coordinate detected in the first orientation of the measuring field, ascertaining the closed trajectory by means of the X-coordinates detected in step and and/or the Y-coordinates detected in step and, wherein, further, a representation of the trajectory is ascertained in step on the basis of the detected X-coordinates and/or the detected Y-coordinates, said representation of the trajectory being parameterized by the orientation angle of the measuring field, which is measured in the direction of the predetermined sense of rotation, proceeding from the orientation angle value of zero degrees. arranging the measuring field in a circular cylindrical bore of a body and transferring the measuring field into a first orientation, irradiating the measuring field with a laser light beam produced by the laser and detecting the X-coordinate and the Y-coordinate of the position of the laser light spot of the laser light beam, which the laser light spot adopts on the measuring field, transferring the measuring field successively in time into at least two further orientations, irradiating the measuring field with the laser light beam in each of the further orientations and detecting the X-coordinate and the Y-coordinate of the positions of the laser light spot of the laser light beam, which the laser light spot adopt on the measuring field in each of the further orientations, wherein the X-coordinate axis and the Y-coordinate axis are oriented at right angles to the centre axis of the bore in the first orientation and also in each of the further orientations and the centre of the coordinate system has a predetermined distance from the inner surface of the bore in the direction of the X-coordinate axis or the Y-coordinate axis, wherein the further orientations differ in terms of the magnitude of the orientation angle (φ R) by which the Y-coordinate axis or the X-coordinate axis is inclined in a predetermined sense of rotation in relation to the Y-coordinate axis or the X-coordinate axis of the measuring field in the first orientation, and wherein the measuring field is transferred into the at least two further orientations in step in such a temporal successive fashion that the orientation angle of each of the further orientations is greater than the orientation angle of each orientation adopted earlier in time, wherein, in the orientation adopted last in time, the magnitude of the orientation angle is at least 90 degrees, assigning the orientation angle value of zero degrees to the X-coordinate and Y-coordinate detected in the first orientation of the measuring field, ascertaining the closed trajectory by means of the X-coordinates detected in step and and/or the Y-coordinates detected in step and, wherein, further, a representation of the trajectory is ascertained in step on the basis of the detected X-coordinates and/or the detected Y-coordinates, said representation of the trajectory being parameterized by the orientation angle of the measuring field, which is measured in the direction of the predetermined sense of rotation, proceeding from the orientation angle value of zero degrees.