A positioning tool for determining the position of the tool in a case downhole. The positioning tool utilizes a detecting unit which includes at least a first magnet and a first sensor in a first plane as well as a second sensor also arranged in the first plane. The first and second sensors are configured to detect changes in a magnetic field generated by the first magnet. The first sensor is arranged at a first distance from the first magnet and the second sensor is arranged at a second distance from the first sensor in the first plane.