Latitude and Longitude (HSC SSCE Mathematics Standard): Revision Notes

Latitude and Longitude

Introduction to Earth's coordinate system

To pinpoint any location on Earth's surface, we use an imaginary grid system made up of lines called parallels of latitude and meridians of longitude. These imaginary lines form circles around the Earth and create a grid pattern that helps us specify exact positions on our planet's surface.

This coordinate system works similarly to how we use street addresses to find buildings, but instead of street names, we use angles measured in degrees.

What is latitude?

Latitude measures how far north or south a location is from the equator. Think of latitude lines as horizontal circles running parallel to the equator.

The equator itself is at $0°$ latitude and divides Earth into two halves:

• The Northern Hemisphere (locations north of the equator)
• The Southern Hemisphere (locations south of the equator)

Latitude is measured as an angular distance from the equator, ranging from $0°$ at the equator to $90°$ at the North and South Poles. The angle is formed at Earth's centre between the equator and a line drawn to the specific parallel of latitude.

Key points about latitude:

• Measured in degrees north (N) or south (S) of the equator
• The equator is at $0°$ latitude
• Maximum latitude is $90°$ (at the poles)
• All latitude lines run parallel to each other
• Also called "parallels of latitude"

What is longitude?

Longitude measures how far east or west a location is from the Greenwich meridian. Longitude lines run vertically from the North Pole to the South Pole.

The Greenwich meridian (also called the Prime Meridian) is at $0°$ longitude and divides Earth into:

• The Eastern Hemisphere (locations east of Greenwich)
• The Western Hemisphere (locations west of Greenwich)

Longitude is measured as an angular distance from the Greenwich meridian, ranging from $0°$ to $180°$ in either direction (east or west). The angle is formed at Earth's centre between the Greenwich meridian and a line drawn to the specific meridian of longitude.

Key points about longitude:

• Measured in degrees east (E) or west (W) of the Greenwich meridian
• The Greenwich meridian is at $0°$ longitude
• Maximum longitude is $180°$ (the International Date Line)
• All longitude lines meet at the North and South Poles
• Also called "meridians of longitude"

The Greenwich meridian

The Greenwich meridian (or Prime Meridian) is a special reference line for measuring longitude. It's an imaginary north-south line that passes through the town of Greenwich in London, England. This location was chosen as the international standard for $0°$ longitude in 1884.

Just as the equator serves as the reference point for measuring latitude, the Greenwich meridian serves as the reference point for measuring longitude.

How to read and write coordinates

When we write the coordinates of a location on Earth, we always follow this order:

For example, Sydney, Australia is located at $(33°\text{S}, 151°\text{E})$. This tells us that Sydney is:

• $33°$ south of the equator
• $151°$ east of the Greenwich meridian

Finding positions on Earth's surface

Let's work through an example to understand how to identify locations using latitude and longitude.

Calculating differences between locations

We can use latitude and longitude to compare the positions of different cities and calculate the angular distance between them.

Remember!