Position Referencing

Ground Position

The ground position is the position on the Earth's surface directly beneath the aircraft.

Dead Reckoning (DR) Position

A DR position is a calculated position based on:

• a previously known position,

• direction of travel,

• speed, and

• elapsed time.

It is therefore an estimated position, rather than a position confirmed by observation.

The term deduced (dead) reckoning is also used in the navigation syllabus.

Fix

A fix is a position established from identifiable external references.

A fix may be obtained by using two or more position lines. Where the position lines intersect is the aircraft's position.

A fix confirms the aircraft's actual position and can be used to check the accuracy of a DR position.

Position Line

A position line is a line along which the aircraft is known to be positioned at a particular time.

A single position line does not show exactly where the aircraft is on the line.

Position lines may be obtained from:

• a road, railway, coastline or other line feature,

• two features that line up, known as a transit, or

• a bearing to or from a known feature.

Place Name

A position may be described using the name of a known place.