Course, leg and route on a plot

A waypoint identifies an intended position on a route. A leg connects successive points, while a route assembles the legs.

The planned course of a leg describes the geographical direction of its line. The heading to steer is another question, because movement through water and the water’s own movement can change the ground track.

A clearly drawn arrow represents a precise intention, but it remains an intention.

On a local plane with north upwards, line orientation can be expressed as a clockwise angle from north. Its length can be expressed in nautical miles.

Endpoint coordinates, course and distance describe related but different aspects. A plot must retain the angle reference and distance scale.

An inclined paper line does not supply a magnetic course merely because it resembles a compass rose.

The actual track may cross the planned line, diverge from it or approach the waypoint from another direction. Perpendicular distance from the line measures lateral displacement; distance to the waypoint is another quantity.

A boat close to the endpoint can still be well away from the leg. Electronic labels such as cross-track error describe this geometry, while sign and display conventions depend on the system.

A usable route needs information absent from the grid: depths, obstructions, restrictions, tides, conditions, manoeuvring space and alternatives. Adding waypoints can create a more detailed line without resolving these questions.

Geometrical construction and nautical appraisal are different tasks. The drawing contains no steering instructions, acceptable offsets or operational waypoint-entry sequence.

A leg has direction. B→A has the same distance as A→B but reciprocal orientation.

In the example, A→B is 090° T and B→A is 270° T. A waypoint name contains no such direction: connection order establishes it.

This makes a waypoint list legible and avoids treating a reversed route as retaining every original course.

A line represents an ideal route axis without width. Physical use involves dimensions, uncertainty and movement beyond that axis.

Drawing a band distinguishes nominal trajectory from space, but a teaching band’s width should not become a valid margin. A system’s ability to connect points automatically solves a geometrical task; appraising the surrounding space is a separate nautical task.