Seatbelt system and method for determining the extension length of a seatbelt system belt strap which is wound on a rotatable belt coil

A method for determining the extension length of a webbing (18) of a seat belt system (10) wound on a rotatable belt reel (28), the belt reel (28) having a fully extended position and a ghost position,

• a) detecting whether a locking tongue (24) of the seat belt system (10) is inserted in the belt buckle (22) of the seat belt system (10),
• b) measuring, when the locking tongue (24) is inserted in the belt buckle (22), the angular position (a) of a measuring element (34) that is coupled to the belt reel (28) by means of a gear unit (36), the rotation of the belt reel (28) being reduced, when the belt reel (28) is adjusted from the ghost position to the fully extended position, by the gear unit (36) to a maximum of 1.0 revolutions of the measuring element (34), and
• c) determining the extension length of the webbing (18) based only on the measured angular position (a) of the measuring element.