A device for providing information on the positioning of a moveable coupling which is located on a movable end of a fluid transfer line of a marine loading system and is adapted for connection to a target duct, the other end of the fluid transfer line being fixed to a base. The device comprises a first apparatus for providing information on the positioning of the coupling. The first apparatus is positioned on the coupling or on a member Immediately neighboring the coupling and includes a first GPS device which provides information on the absolute positioning of the coupling in space. The device comprises a second apparatus adapted to cooperate directly with the first apparatus and provides information on the positioning of the base. The second apparatus is disposed on the base or on a member immediately neighboring the base and provides, on the basis of the information on the positioning of the base and the information on the positioning of the coupling, information on the relative positioning of the coupling directly relative to the base. Alternatively, the first means is adapted to provide information on the absolute positioning of the coupling in space, the base has a fixed position in space, and the device comprises a calculator for calculating, on the basis of the information on the absolute positioning of the coupling and data on positioning of the base, information on the relative positioning of the coupling directly relative to the base.