Method and laboratory system for handling sample tube racks

A method of operating a storage section (14) of a laboratory system, the storage section (14) comprising (a) a plurality of shelves (110) for storing a plurality of sample tube racks, the shelves including a top shelf and a bottom shelf, the top and bottom shelves having a first end and an opposite second end, and (b) a robotic transfer system (510) for loading sample tube racks into the storage section (14) and retrieving sample tube racks from the storing section (14), comprising the following steps:

• the robotic transfer system (510) moving along the top shelf or the bottom shelf from the first end thereof to the opposite second end thereof, identifying a plurality of markings defining a plurality of individual storage rack end positions, and measuring a plurality of distances between the individual storage rack end positions defined by such markings;
• and
• storing absolute coordinates of the individual storage rack end positions from the identified markings and measured distances.