Cartographic Skills » Co-ordinates and Grid References

What you'll learn this session

Study time: 30 minutes

How to use latitude and longitude to locate places globally
How to read and use four-figure grid references on maps
How to find and give six-figure grid references for precise locations
Practical skills for navigating using Ordnance Survey maps
How to apply these skills to fieldwork and exam questions

Introduction to Cartographic Skills: Coordinates and Grid References

Maps are essential tools for geographers, but they're only useful if you can pinpoint exact locations on them. That's where coordinates and grid references come in! These systems help us locate places precisely, whether we're finding a country on a world map or a specific tree in a local park.

Key Definitions:

Cartography: The science and practice of making maps.
Coordinates: A set of numbers and/or letters that identify a specific position on a map.
Grid reference: A map reference indicating a location in terms of a series of vertical and horizontal grid lines.
Latitude: Imaginary lines that run east to west around the globe, measuring distance north or south of the Equator.
Longitude: Imaginary lines that run north to south around the globe, measuring distance east or west of the Prime Meridian.

🌎 Global Coordinates: Latitude and Longitude

Latitude and longitude form a global grid system that allows us to locate any place on Earth. Think of it as the planet's address system!

Latitude lines run horizontally (east-west) and measure how far north or south a place is from the Equator (0°). They range from 0° to 90°N (North Pole) and 0° to 90°S (South Pole).

Longitude lines run vertically (north-south) and measure how far east or west a place is from the Prime Meridian (0°), which runs through Greenwich, London. They range from 0° to 180°E and 0° to 180°W.

🗺 Reading Coordinates

Coordinates are always given in the order: latitude, longitude.

For example, the coordinates of London are approximately 51.5°N, 0.1°W.

The coordinates of Sydney, Australia are approximately 33.9°S, 151.2°E.

Notice that we specify N/S for latitude and E/W for longitude to clarify which side of the Equator or Prime Meridian the location is on.

Grid References on Maps

While latitude and longitude work well for global locations, most local maps use a simpler grid reference system. In the UK, Ordnance Survey maps use a grid of squares to help pinpoint locations.

Four-Figure Grid References

A four-figure grid reference identifies a specific 1km square on a map. It's made up of:

Two digits for the eastings (horizontal lines)
Two digits for the northings (vertical lines)

How to find a four-figure grid reference:

Find the grid square you're interested in.
Look at the bottom left corner of that square.
Read the easting value first (the number along the bottom of the map).
Then read the northing value (the number up the side of the map).
Put these together as four digits, e.g., 3246.

Remember the helpful phrase: "Along the corridor, up the stairs" to remember the order: eastings first, then northings.

💡 Quick Tip

When giving grid references, always give the eastings (horizontal) first, then the northings (vertical). Think "along the corridor, then up the stairs" - you go along before you go up!

Six-Figure Grid References

Four-figure grid references only get you to a 1km square. For more precision, we use six-figure grid references, which can pinpoint a location to within 100 metres.

How to find a six-figure grid reference:

Find the four-figure grid reference for your square.
Imagine the square is divided into 10 equal parts along both axes.
Estimate how many tenths across the easting your location is (e.g., 3.7).
Estimate how many tenths up the northing your location is (e.g., 4.5).
Add these tenths as a third digit to each part of your four-figure reference.
So 3246 becomes 374465.

📏 Four-Figure Example

The church is in grid square 2348.

This means it's somewhere within the 1km square where easting 23 meets northing 48.

🔍 Six-Figure Example

The church is at 236485.

This means it's 6/10 of the way across square 23 and 5/10 of the way up square 48.

⚠ Common Mistakes

Mixing up the order (remember: eastings first!)

Not reading from the bottom-left corner of the square

Forgetting to estimate tenths accurately for six-figure references

Practical Applications

Understanding coordinates and grid references isn't just about passing exams - these are practical skills used in many real-world situations:

🗺 Navigation and Fieldwork

During geography fieldwork, you'll often need to record the exact locations of your data collection points. Six-figure grid references are perfect for this.

When hiking or orienteering, grid references help you plan routes and identify landmarks.

Emergency services use grid references to locate people who need help in remote areas.

📚 Exam Technique

In your iGCSE Geography exam, you might be asked to:

Give the grid reference for a specific feature
Identify what's located at a given grid reference
Describe the location of something using grid references
Calculate distances between grid references

Practice these skills regularly with different maps to build confidence!

Case Study Focus: Ordnance Survey Maps

Ordnance Survey (OS) maps are the UK's official mapping agency. Their maps use a National Grid system that divides the UK into 100km squares, each identified by two letters (e.g., TQ for part of London). These letters are followed by the grid references we've been learning about.

OS maps come in different scales:

1:25,000 scale (Explorer maps) - Great for walking and detailed features
1:50,000 scale (Landranger maps) - Good for driving and broader planning

The grid lines on OS maps are exactly 1km apart at the scale of the map, making grid references easy to use.

Digital Mapping and GPS

While traditional grid references are still important, modern technology has given us new ways to pinpoint locations:

GPS and Digital Coordinates

Global Positioning System (GPS) uses satellites to determine exact locations on Earth. GPS coordinates are usually given in decimal degrees of latitude and longitude (e.g., 51.5074°N, 0.1278°W for London).

Many smartphone apps and websites now use these digital coordinates, but the principles are the same as traditional latitude and longitude.

Some digital mapping systems use different coordinate systems like UTM (Universal Transverse Mercator), but the concept of a grid remains.

📝 Practice Exercise

Find an Ordnance Survey map of your local area (your school might have some, or you can view them online at OS Maps).

Try these activities:

Find the four-figure grid reference for your school or home
Now find the six-figure grid reference for the same location
Identify what's located at grid reference 395842 (this is just an example - use coordinates relevant to your map)
Calculate the straight-line distance between two grid references

Summary: Key Points to Remember

Latitude and longitude form a global coordinate system (latitude measures north-south position, longitude measures east-west position)
Grid references on maps help us pinpoint specific locations
Four-figure grid references identify a 1km square
Six-figure grid references provide precision to 100 metres
Always give eastings first, then northings ("along the corridor, up the stairs")
These skills are essential for fieldwork, navigation and exam success

With practice, reading coordinates and grid references will become second nature. These skills will help you in your geography studies and beyond!

🧠 Test Your Knowledge!