Definition
The four principal directions on a compass: north (000°/360°), east (090°), south (180°), and west (270°). They divide the compass rose into four equal 90° quadrants and serve as the primary reference directions for navigation, charting, and ATC instructions.
Plain English
The four main directions — north, east, south, and west — spaced 90 degrees apart on the compass.
Context Anchor
Used in IFR holding clearances when ATC tells a pilot which direction to hold from a fix.
Derivation
Cardinal comes from the Latin cardinalis, meaning 'principal' or 'hinge-like' — from cardo, a hinge. The idea is that everything else 'hinges' on these four main directions. All other compass headings are described relative to them.
Why Pilots Care
Holding instructions commonly use cardinal directions for clear, concise IFR clearances that reduce the chance of misinterpretation.
Intuition Check
Do not assume “cardinal compass points” means only north, east, south, and west here. In FAA holding instructions, it commonly includes the eight named directions: north, northeast, east, southeast, south, southwest, west, and northwest. Also, the named point describes where the hold is located; it is not automatically the heading to fly.
Example Sentence 1
ATC instructed the pilot to hold east of the VOR, using a cardinal compass point to define the holding side.
Example Sentence 2
The clearance read 'hold west on the 270 radial,' using one of the cardinal compass points for simplicity.