PT 7, Ch 9, Section 3.1.11 states that a speed log or alternative means of indicating the ship's speed and distance through water is to be provided. The speed through water measurement is to be used directly by the ARPA as an aid to collision avoidance. PT 7, Ch 9, Section 3.1.12 states that a speed log or alternative means of indicating the ship’s speed and distance over ground is to be provided, which is to be separate from the device required by Pt 7, Ch 9, 3.1 Navigation workstation 3.1.11. Speed over ground is to be indicated in both the fore-aft and athwartships directions.

To satisfy the requirements of PT 7, Ch 9, Section 3.1.11, M/S MERSol is outfitted with an electromagnetic speed log, often referred to as EM log. The EM log can measure the speed of the vessel by using the effects of magnetism in moving water, the EM log has a single transducer mounted inside a gate valve connected to the hull. The EM log is powered by main and emergency power sources and is connected to both X and S ARPA/radars.

To satisfy the requirements of PT 7, Ch 9, Section 3.1.12, M/S MERSol is outfitted with (D)GPS systems as earlier described. The (D)GPS systems are connected to both ARPA systems and provide it with information regarding speed and distance measured over ground.


Speed log system electrical drawing, M/S MERSol.

Last modified: Saturday, 18 March 2023, 5:09 AM