Classification and Equipment Requirements of Ship Compasses
Many sailors, when they first board a ship, will find various types of compasses on board, such as magnetic compasses, standard compasses, steering compasses, electric compasses, repeater compasses, and gyro compasses. These compasses have different names and functions. However, distinguishing them carefully, there are only two types of compasses widely purchased and used in the mainstream market: magnetic compasses and electric compasses. Understanding the classification of compasses and the international regulatory requirements for their equipment will help you quickly find the compass suitable for your vessel when purchasing ship compasses.
Overview
Classification of Magnetic Compasses:
Based on Structure:
Liquid Compass: A compass in which the compass card is immersed in a mixture of alcohol and distilled water. Due to the damping effect of the liquid when the vessel swings, the directional stability of the compass is good. Liquid compasses are widely used in the market.
Dry Compass: The directional system is not immersed in liquid, and its directional stability is unstable. It has been phased out.
Based on Purpose and Installation Position:
Standard Compass: Installed on the fore-and-aft line of the open deck above the bridge, with a high position, good visibility, minimal magnetic interference on the ship, and high accuracy. The compass card and baseline can be projected onto the bridge for the helmsman to read the heading with the help of shading and projection devices.
Helm Compass: Installed directly in front of the steering wheel inside the bridge for steering.
Emergency Compass: Installed on the fore-and-aft line in front of the emergency rudder at the stern, used when the steering gear fails.
Boat Compass: A small liquid compass used on yachts and lifeboats, with the compass card coated with a fluorescent substance.
Based on Construction:
Table Compass: A small liquid compass used as a helm compass for small vessels such as wooden sailing fishing boats and non-steel small boats.
Stand Compass: Used as a standard magnetic compass for large and medium-sized vessels.
Reflector Compass and Projection Compass: Standard compasses installed on the open deck above the bridge that can project and reflect compass cards into the bridge.
Electric Compass:
The electric compass, also known as a gyro compass, typically consists of a master compass, repeater compass, power transformer, control box, and operating box. The repeater compass repeats the heading of the master compass and can be directional or heading repeater compasses. Directional repeater compasses are located on both sides of the bridge to display directions, while heading repeater compasses are located in the wheelhouse to indicate headings.
SOLAS Convention Requirements for Ship Compass Equipment:
Ships below 300 gross tons are required to be equipped with a steering magnetic compass or a reflector magnetic compass.
Ships of 300 gross tons and above are required to be equipped with a standard magnetic compass and a spare standard magnetic compass. Ships equipped with a steering magnetic compass or gyro compass may not need a spare standard magnetic compass.
Passenger ships of 3000 gross tons and above and cargo ships of 5000 gross tons and above are required to be equipped with a gyro compass.
If directional repeater compasses are set on both wings of the bridge outside the wheelhouse and the top of the bridge deck is shaded, an additional repeater compass should be installed on the open deck above the wheelhouse.
Heading repeater compasses should be installed at least at the main steering position and the emergency steering position.
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