Latitude & Longitude – SS1 Geography Lesson Note (First Term)

Latitude and longitude are imaginary lines drawn on the globe to locate places on the earth’s surface. Latitude is the angular distance of a point measured in degrees from the centre of the earth, and its lines run parallel to the equator. Longitude is the angular distance measured in degrees east and west of the Greenwich Meridian.

Behavioural objectives

By the end of the lesson, students should be able to:

• define latitude and longitude;
• list the important lines of latitude and longitude;
• state the uses of lines of latitude and longitude;
• state the similarities and differences between latitude and longitude;
• distinguish between a great circle and a small circle.

What is latitude?

Latitude is the angular distance of a point on the earth’s surface measured in degrees from the centre of the earth. Lines of latitude are parallel to the equator. The Equator divides the earth into two halves known as the Northern and Southern Hemispheres. Lines of latitude are sometimes called parallels.

Important lines of latitude

1. The Equator: 0°
2. North Pole: 90°N
3. South Pole: 90°S
4. Tropic of Cancer: 23½°N
5. Tropic of Capricorn: 23½°S
6. Arctic Circle: 66½°N
7. Antarctic Circle: 66½°S

Uses of lines of latitude

Lines of latitude are used to:

1. determine the exact location of a place on the atlas map;
2. calculate the distance between two places on the earth’s surface.

What is longitude?

Longitude is an angular distance measured in degrees east and west of the Greenwich Meridian. It is an imaginary line drawn on the globe (earth) running from north to south at right angles to the parallels.

The longitude passing through London and Accra is called the Great, Prime or Greenwich Meridian, and it is on longitude 0°. All lines of longitude are called meridians.

Important lines of longitude

1. Long. 0° (Prime Meridian)
2. Long. 45°E
3. Long. 45°W
4. Long. 90°E
5. Long. 90°W
6. Long. 180°E, etc.

Uses of lines of longitude

Lines of longitude are used to:

1. calculate local time;
2. determine the exact location of places on the atlas map.

How are lines of latitude and longitude alike and different?

Similarities between lines of latitude and meridians

1. Both are used for the location of places on the map.
2. Both are numbered in degrees.
3. Both are imaginary lines drawn on the globe.
4. Both contain great circles.

Differences between lines of latitude and lines of longitude

What are a great circle and a small circle?

Great circle

A great circle is any line that divides the earth into two halves or hemispheres. The centre of a great circle is also the centre of the earth.

Two opposite lines of longitude make a great circle, for example long. 0° with long. 180°W and 180°E, long. 30°W with long. 150°E, and long. 110°W with long. 70°E.

Small circle

A small circle is any line that does not divide the earth into two halves or hemispheres. All lines of latitude are small circles except the Equator. Examples are the Tropic of Cancer and the Tropic of Capricorn.

Evaluation

1. Define latitude and longitude.
2. List the seven important lines of latitude and give their values.
3. State two uses of lines of longitude.
4. State three differences between lines of latitude and lines of longitude.
5. Distinguish between a great circle and a small circle.

Assignment

1. Lines of longitude can best be described as (a) the angular distance of a place north or south of the equator (b) semi-circle on the globe (c) imaginary lines on the earth’s surface joining the north and south poles.
2. The angular distance of a point on the earth’s surface measured in degrees from the centre of the earth is known as (a) latitude (b) longitude (c) international date line.
3. The shortest flying route between any two points on the earth’s surface lies along the (a) Tropic of Capricorn (b) Tropic of Cancer (c) great circle.
4. A great circle can be described as (a) a line of longitude (b) a line of latitude (c) the shortest distance between two points on the globe.
5. The following are the similarities between lines of longitude and latitude except (a) both are used to calculate the local time of a place (b) both are numbered in degrees (c) both contain great circles.