Abstract: The apparatus includes transmitter-receiver units (10, 20) for emitting acoustic signals in the form of beams (F1, F2) directed rearwardly of the stern and for receiving acoustic signals reflected by the fixed structure (B, C). The number of transmitter-receivers and the beam angles of the respective beams are determined so as to include substantially the entire area behind the stern in their field of view. Each transmitter-receiver includes a transducer for converting input electrical signals into output acoustic signals and for converting reflected acoustic signals into output electrical signals which are supplied to an electronic processor unit. On the basis of electrical input and output signals, the processor unit determines the instantaneous distance between the vessel and the fixed structure. A visual and/or acoustic signalling device is connected to the processor unit for emitting a visual and/or acoustic signal in real time indicating the instantaneous distance determined.

Abstract: A boat has installed therein a primary propulsion system to produce a thrust at least in the longitudinal direction, manual controls for controlling the primary propulsion system, a transverse propulsion system for producing a transverse thrust, and a joystick control for controlling the primary and transverse propulsion systems for navigation at slow speed or in docking manoeuvres. An electronic control unit controls the propulsion systems and receives information on the instantaneous speed of the boat and on the instantaneous distance between the boat and an obstacle such as the coast, the bottom or floating or half-submerged bodies. The electronic unit is so arranged that when the boat is located at a distance from an obstacle less than a predetermined distance it controls the propulsion systems to reduce the speed of the boat to below a predetermined limit, disables the manual controls of the primary propulsion system and enables the joystick control.

Abstract: A boat has installed therein a primary propulsion system to produce a thrust at least in the longitudinal direction, manual controls for controlling the primary propulsion system, a transverse propulsion system for producing a transverse thrust, and a joystick control for controlling the primary and transverse propulsion systems for navigation at slow speed or in docking manoeuvres. An electronic control unit controls the propulsion systems and receives information on the instantaneous speed of the boat and on the instantaneous distance between the boat and an obstacle such as the coast, the bottom or floating or half-submerged bodies. The electronic unit is so arranged that when the boat is located at a distance from an obstacle less than a predetermined distance it controls the propulsion systems to reduce the speed of the boat to below a predetermined limit, disables the manual controls of the primary propulsion system and enables the joystick control.

Abstract: The apparatus includes transmitter-receiver units (10, 20) for emitting acoustic signals in the form of beams (F1, F2) directed rearwardly of the stern and for receiving acoustic signals reflected by the fixed structure (B, C). The number of transmitter-receivers and the beam angles of the respective beams are determined so as to include substantially the entire area behind the stern in their field of view. Each transmitter-receiver includes a transducer for converting input electrical signals into output acoustic signals and for converting reflected acoustic signals into output electrical signals which are supplied to an electronic processor unit.