Container crane comprising reference marker

A container crane comprising:

• a spreader configured to controllably attach to a container;
• a container trolley to which the spreader is attached via cables, the container trolley being provided on an upper part of the container crane and being horizontally movable along a first direction;
• a first sensor arrangement mounted on the container trolley, the first sensor arrangement being usable to determine a position of the container;
• a second sensor arrangement being usable to determine a position of a target;
• and
• at least one reference marker provided fixed, in at least two dimensions, to a horizontal support provided along the first direction between vertical structures of the container crane, the at least one reference marker being provided vertically lower than the first sensor arrangement and the at least one reference marker being detectable by the first sensor arrangement, and
• wherein the second sensor arrangement is provided on a sensor trolley, being movable along the horizontal support, and wherein the at least one reference marker is provided on the sensor trolley, or
• wherein the second sensor arrangement comprises a plurality of sensors fixed to the horizontal support and wherein the at least one reference marker is provided fixed to the horizontal support.