The Earth
The Solar System & Time
Charts
Using Aeronautical Charts
Basics of Navigation
Distance, Speed & Time
Vertical Navigation
Fuel Planning
Practical Navigation Techniques
Radio Navigation
Practice Exam

Lines on the Earth

Great Circles

A great circle is any circle that is drawn around the Earth where the centre of the circle is the centre of the Earth. For example, the equator is a great circle.

The shortest distance between two points on the surface of the Earth is always along the great circle that passes between the two points. This is known as the great circle distance.

The shortest distance between two points on the surface of the Earth is always the great circle distance

Small Circles

A small circle is any circle that is drawn around the Earth where the centre of the circle is not the centre of the Earth.

Another way to think of it is that all great circles will divide the Earth into 2 equal parts, but all small circles will not.

All parallels of latitude (except the equator) are small circles.

Rhumb Lines

A rhumb line is a line that crosses all meridians of longitude at the same angle.

All parallels of latitude are rhumb lines.