Understanding Different North References in Navigation

True North (Geodetic North)

True North refers to the direction along the Earth’s surface toward the geographic North Pole, the fixed point where the Earth’s axis of rotation intersects its surface in the Northern Hemisphere. It remains constant over time and serves as the fundamental reference point for geographic coordinates and navigation.

Magnetic North

Magnetic North is the direction indicated by a magnetic compass. Unlike True North, Magnetic North is not fixed—it shifts gradually over time due to changes in the Earth’s magnetic field. The movement, known as magnetic drift, varies in speed and direction, requiring periodic updates to navigation charts and compasses.

Grid North

Grid North refers to the direction of vertical grid lines on a map projection, such as those used in the National Grid Reference System. It represents the northward direction along the map’s grid lines, which are aligned with a central meridian rather than True North. The difference between Grid North and True North depends on the mapping system and geographic location.

Magnetic North vs. the Earth’s Magnetic Field

Interestingly, the Earth’s Magnetic North Pole is actually the South Pole of the planet’s magnetic field. This is because the north-seeking pole of a compass needle (which we call the “North Pole”) is naturally attracted to it—since opposite poles attract.

Understanding these different references—True North, Magnetic North, and Grid North—is essential for accurate navigation in aviation, marine travel, and land-based surveying.