The Difference Between Geographic and Magnetic North on Your Compass and Map

When navigating, it is crucial to understand the distinction between two types of north: Geographic North and Magnetic North. While Geographic North is straightforward and consistent, Magnetic North, accessible through your compass, can vary significantly. This article will explore these concepts, their differences, and why it is important to be aware of declination.

Understanding Geographic North

Geographic North Pole is a fixed point on the surface of the Earth towards which the planet rotates. It is the Earth's axis of rotation and is the centre of the planet's north-south axis.

Understanding Magnetic North

Magnetic North Pole, on the other hand, is a specific point in northern Canada that magnetic compasses point towards—or more precisely, what compasses use to align with Earth's magnetic field. Unlike the fixed geographic north, the magnetic north pole is constantly in motion due to the rotation of the Earth and changes in its magnetic field.

The Concept of Declination

The discrepancy between Geographic North and Magnetic North is known as 'declination.' This angle, varying in degree, is the difference between the direction a compass points to the magnetic north and the true direction to the geographic north.

Implications of Declination

Most maps and nautical charts include a declination legend, displaying how much this angle changes over time. This is essential for those engaging in navigation, such as sailors, pilots, and hikers, as it allows them to accurately locate their positions. Failing to account for declination can lead to errors in navigation.

Causes of Declination

The movement of the Earth's magnetic poles is driven by the flow of the liquid core, primarily composed of iron, which circulates with the Earth's rotation. This flow is not static and can shift dramatically. Every few thousand years, the Earth's magnetic poles are reversed, a process known as geomagnetic reversal.

Annual Changes in Declination

The rate and direction of declination are not constant. For instance, over the last century, the Magnetic North Pole has gradually moved northward. Maps and charts should be regularly updated to reflect the current declination. This variation requires navigators to adjust their compass bearings accordingly, especially when using old maps.

Other Factors Affecting Magnetic North

There are additional factors that can affect the magnetic direction of a compass:

Irregular Magnetic Attractions

Some areas on Earth have stronger or weaker magnetic attractions, altering the direction in which a compass needle points. This phenomenon is known as anisotropy. Areas near large masses of iron, such as a car's engine, can also affect the compass, a phenomenon called deviation.

Technological Interference

Modern electronic devices can sometimes distort the magnetic field, leading to deviations from true north. This is particularly relevant in dense urban areas with many buildings and metals.

Practical Implications for Navigators

Understandably, the differences between geographic and magnetic north can be significant for those relying on maps and compasses for navigation. For sailors or pilots, a wrong reading caused by declination or deviation can result in severe consequences, such as being off course and possibly in danger.

Conclusion

Understanding the distinctions between geographic and magnetic north is fundamental for accurate navigation. By knowing and using the concept of declination, one can make informed decisions to improve their navigation skills. This knowledge is crucial for anyone who relies on maps and compasses for any form of navigation, ensuring they can reach their intended destination safely and accurately.

Note: For updated and accurate information, always refer to the most recent charts, maps, and nautical publications.