Compass is a navigational equipment used to get the directional sense with respect to a geographical reference point. Unlike a clock’s dial, on a compass, the dial has got a specific name. It’s called the compass rose. It is marked with the 4 cardinal directions namely North, East, South & West. For industrial uses such as found in the compasses on ships, we have intermediary angles that are laid down keeping the North on 0 Degrees and moving in a clockwise fashion we get East at 90 Degrees, South at 180 degrees and so on.
For better understanding, here we will discuss 2 important types of compasses that a sailor should be aware of –
- Magnetic Compass
- Gyro Compass
Table of Contents
What is a magnetic compass?
The magnetic needle on the compass aligns itself with the earth’s magnetic lines and points in the North-South direction. This property of the needle is used in a compass to indicate the magnetic north. Magnetic compasses were the only source of directional sense in ancient times when wooden ships were used for all ocean-going purposes but with advancements in shipbuilding technologies and navigational systems, the sole reliance on magnetic compasses came down heavily after that.
Still, magnetic compasses are highly popular among sailors and are one of the most tattooed designs. Ship compass tattoos are believed to bring luck to a seafarer and that’s why it still finds its place on the ship as well as on the sailor’s body.
In earlier ships, the magnetic compass was housed in a waist high wooden structure called a binnacle. Binnacle was placed on the deck in front of the helmsman and it was fitted with other navigational equipments too for a quick reference. The binnacle also used to be fitted with 2 iron balls to reduce the effects of other ferromagnetic substances on the ship.
Are magnetic compasses still used onboard ships?
No doubt magnetic compass is an ancient thing and gyrocompass is used as the primary compass on ships but still, a corrected magnetic compass can prove to be a lifesaver if the need arises because of the fact that we don’t need any power source or any inputs from satellites to use a magnetic compass on ships. In modern-day merchant vessels, a magnetic compass is fitted on the monkey island (The top of the ship superstructure) and is visible to the navigating crew on the bridge via periscope arrangements.
What are gyrocompasses?
It is an electrically powered navigational equipment that uses the earth’s rotation and a high rpm spinning wheel to point in a specific direction which is the earth’s true north. The biggest advantage of using a gyro compass on a ship is that it is not affected by the ferromagnetic material of which the ship’s hull is made.
Usage of Gyro Compass
The gyroscope is the heart of the gyrocompass. It can be considered as a spinning wheel that has the ability to maintain its orientation throughout. Nowadays it is widely used in electronic gadgets. If you are reading this article on a screen which you are holding in your hands, chances are that you are holding a gyroscope too. To know more about how gyroscopes work read here.
It has been observed that a gyrocompass shows deviation from the true north when it approaches the North and the South Pole. In order to correct such errors, the ship’s gyrocompass is fed with inputs from the global positioning system (GPS).