Abstract: A laser head is placed roughly centrally in a hollow cylinder with the capacity to rotate. The pertinent rotation motion of the laser head takes place essentially around the lengthwise axis of the hollow cylinder, while the alignment of the laser beam agrees only approximately with the lengthwise axis of the hollow cylinder. When the laser head turns, a hyperboloid-shaped family of light beams is generated. These light beams produce an essentially circular projection pattern on a target attached outside of the hollow cylinder. The projection pattern with its center defines a point on an ideal axis (core) which is assigned to the hollow cylinder. The invention is suitable especially for measuring shaft tunnels of ships, but also for laying piping systems with large dimensions such as pipelines.