Understanding Great and Small Circles
In geography, great circles and small circles are vital for navigation and mapping. A great circle is the largest circle that can be drawn on a sphere, dividing it into two equal halves. The equator is a common example of a great circle. In contrast, a small circle is any circle on the sphere that does not divide it into equal halves, such as the Tropic of Cancer.
To locate a place on Earth using latitude and longitude:
- Latitude measures how far north or south a point is from the equator, ranging from 0° at the equator to 90° at the poles.
- Longitude measures how far east or west a point is from the Prime Meridian, ranging from 0° to 180°.
For example, the coordinates of Nairobi, Kenya, are approximately 1.2861° S (latitude) and 36.8219° E (longitude). This means Nairobi is located just south of the equator and east of the Prime Meridian.
Key points to remember
- Great circles divide the sphere into two equal halves.
- Small circles do not divide the sphere equally.
- Latitude measures north-south position from the equator.
- Longitude measures east-west position from the Prime Meridian.
- Coordinates are written as (latitude, longitude).
Worked example
Define a great circle and provide an example.
- A great circle is the largest circle on a sphere, e.g., the equator.