Definition
A method of navigation used in polar regions where conventional reference to true or magnetic north becomes unreliable. A grid of parallel lines is overlaid on the chart, all aligned with the Greenwich (Prime) Meridian, and headings are flown relative to grid north rather than true or magnetic north.
Plain English
Near the poles, normal compass directions stop working well because the meridians all converge and the magnetic compass becomes erratic. Grid navigation solves this by drawing a set of straight, parallel reference lines across the chart so pilots can fly steady headings without worrying about the poles distorting direction.
Context Anchor
Seen in polar, high-latitude, long-range, and military navigation discussions.
Derivation
‘Grid’ comes from the Latin craticula, meaning a small gridiron or framework of crossed bars. The image fits: a uniform pattern of parallel lines laid over the chart, providing a consistent reference where natural directions (true and magnetic north) no longer behave predictably.
Why Pilots Care
Allows precise heading and position reference in polar regions where magnetic compasses become unreliable due to proximity to the magnetic poles.
Grounding Statement
Near the poles, longitude lines crowd together and a magnetic compass may not point reliably, so a chart grid gives the pilot a steadier way to measure direction.
Intuition Check
Grid navigation does not mean simply following the square boxes on a chart. It means using a planned grid direction system as the reference for courses and headings.
Example Sentence 1
Crews flying transpolar routes switch to grid navigation once they enter high latitudes, where magnetic headings are no longer dependable.
Example Sentence 2
Grid navigation charts helped the pilot plot a direct course across the Arctic without compass deviation issues.