Definition
The printed lines and numerals on the magnetic compass card that divide the card into measurable units of heading, typically every 5 degrees, with numerals shown every 30 degrees. They are the scale a pilot reads against the lubber line to determine the aircraft's magnetic heading.
Plain English
The little lines and numbers printed around the compass that you read to see which direction the aircraft is pointing.
Context Anchor
Seen on the face of the basic magnetic compass, especially when reading or confirming a heading in the cockpit.
Derivation
From the Latin 'gradus' meaning 'step' or 'degree.' Graduation marks are literally the 'steps' along the scale — each mark is one step in the measurement, like the steps on a ruler.
Why Pilots Care
Clear, accurate graduation marks are essential for precise heading control and navigation.
Analogy
Graduation marks on a compass work like the tick marks on a ruler. The ruler marks help you read length; compass marks help you read direction.
Intuition Check
Graduation does not mean completing a course here. It means the small marks that divide a measuring scale into readable steps.
Example Sentence 1
The pilot lined up the lubber line with the 270 graduation mark to confirm a westerly heading.
Example Sentence 2
Worn graduation marks on the compass card made it hard to hold a precise heading in turbulence.