What is deviation in navigation?

What is deviation in navigation?

• A. How much the compass deviates due to external forces and metals
• B. The turning speed of a ship
• C. The difference between magnetic north and true north
• D. The amount of wear on the compass

Answer: (A)

Deviation is the error in a ship’s magnetic compass caused by the ship’s own magnetic field. The hull, engines, electrical gear, and other ferrous metal on board create local magnetic fields that pull the compass needle away from true magnetic north, so the reading you see isn’t the actual direction over the Earth’s field. This deflection changes with heading and what equipment is on or off, so sailors determine a deviation table (a compass correction card) to know how much to adjust for each course. It’s different from variation, which is the difference between magnetic north and true north at a location, and it’s also different from wear or mechanical issues with the compass.

Deviation is the error in a ship’s magnetic compass caused by the ship’s own magnetic field. The hull, engines, electrical gear, and other ferrous metal on board create local magnetic fields that pull the compass needle away from true magnetic north, so the reading you see isn’t the actual direction over the Earth’s field. This deflection changes with heading and what equipment is on or off, so sailors determine a deviation table (a compass correction card) to know how much to adjust for each course. It’s different from variation, which is the difference between magnetic north and true north at a location, and it’s also different from wear or mechanical issues with the compass.