MARITIME – ELECTRICAL & ELECTRONIC CALCULATOR
Compass Swing Correction
A precise tool.
What is the Compass Swing Correction & How does it work?
The magnetic compass is affected by both the Earth’s magnetic field and the vessel’s own magnetic influences. The latter, known as deviation, varies with the ship’s heading and must be quantified to obtain accurate bearings. During a compass swing, the navigator records the observed compass bearing for a series of known true headings. By applying the known magnetic variation, the deviation for each heading can be calculated, forming the basis of a deviation card. The deviation card is then used to correct future compass readings, ensuring safe navigation. The relationship between observed bearing (B), true heading (H), magnetic variation (V), and deviation (D) is expressed by the formula below.
D = B – (H + V)
D = Deviation (°)
Parameters
Result
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Frequently Asked Questions
What is compass swing correction?
Compass swing correction involves measuring the difference between true headings and observed compass bearings to create a deviation card for more accurate navigation.
Why do we need a deviation card?
A deviation card helps correct for magnetic influences on the vessel, ensuring that navigators can obtain accurate bearings for safe maritime travel.
How is magnetic variation used in compass swing correction?
Magnetic variation is applied to convert observed compass bearings into true headings during a compass swing, allowing for the calculation of deviation.
What are some common causes of compass deviation?
Common causes include the ship’s own magnetic fields from engines, steel structures, and other equipment that affect the compass reading.
How often should a compass swing be performed?
A compass swing should be performed regularly, typically at least once a year or whenever there are significant changes to the vessel’s structure or equipment.
Can deviation be corrected while underway?
While some deviation can be corrected using magnetic compensators, a comprehensive correction requires a full swing and updating of the deviation card.
What is the purpose of a magnetic compass in navigation?
The magnetic compass provides navigators with a heading reference to steer the vessel on a desired course relative to true north, accounting for magnetic variation.
Results are for informational purposes only and do not constitute professional advice.