Cartographic Skills » Topographical Maps

What you'll learn this session

Study time: 30 minutes

How to read and interpret topographical maps
Understanding contour lines, scale and direction
Identifying physical and human features on maps
Calculating distances, areas and gradients
Using grid references to locate features
Recognising map symbols and their meanings

Introduction to Topographical Maps

Topographical maps are detailed, accurate representations of natural and human-made features on the Earth's surface. They're like the superhero of maps - they show everything from hills and valleys to buildings and bridges! These maps are essential tools for geographers, hikers, urban planners and many others who need to understand the landscape.

Key Definitions:

Topographical map: A detailed map showing both natural and human-made features of an area, including relief (the shape of the land).
Contour lines: Lines on a map that join points of equal height above sea level.
Relief: The shape and height of the land surface.
Scale: The ratio between distances on the map and actual distances on the ground.

🗺 Map Scale

Map scale tells us how much the real world has been shrunk to fit on the map. It can be shown in three ways:

Ratio scale: Like 1:50,000 (1 cm on map = 50,000 cm or 500 m on ground)
Linear scale: A line showing distances (like a ruler on the map)
Statement scale: Written out, e.g., "One centimetre represents half a kilometre"

📍 Direction and Bearings

Maps always have north at the top. You can find direction using:

Cardinal points: North, South, East, West
Compass bearings: Measured in degrees clockwise from north (0°)
Remember: a bearing is always given as a 3-digit number (e.g., 090° not just 90°)

Understanding Grid References

Grid references help us pinpoint exact locations on a map. Think of them like coordinates for a giant game of battleships!

📌 Four-Figure Grid References

These identify 1km squares on the map:

Read the eastings (horizontal lines) first - "along the corridor"
Then read the northings (vertical lines) - "up the stairs"
Example: 3246 means 32 across, 46 up

🔍 Six-Figure Grid References

These pinpoint locations more precisely (to 100m):

Find the 1km square using the four-figure method
Estimate tenths within that square for both eastings and northings
Example: 326468 means 32.6 across, 46.8 up

Contour Lines and Relief

Contour lines are the secret to understanding the 3D shape of the land from a 2D map. They connect points of equal height above sea level, allowing us to visualise mountains, valleys and slopes.

⛰ Hills and Mountains

Contour lines form roughly circular patterns. The closer together the lines, the steeper the slope. The innermost contour is usually the highest point (summit).

🕋 Valleys and Rivers

Contour lines form V-shapes pointing uphill. The V-shape points upstream, showing the direction water flows. The closer the contours, the steeper the valley sides.

🗻 Cliffs and Gentle Slopes

Very close contour lines indicate steep slopes or cliffs. Widely spaced contour lines show gentle slopes. Completely flat areas have no contour lines.

Contour Patterns

Learning to recognise these common contour patterns will help you visualise the landscape:

Concentric circles: Hills or mountains
V-shapes: Valleys (V points uphill)
U-shapes: Spurs or ridges (U points downhill)
Uniform spacing: Constant slope
Very close lines: Steep slope or cliff
Widely spaced lines: Gentle slope

The contour interval is the vertical height difference between adjacent contour lines, usually 5m, 10m or 25m on most maps. This is always stated in the map key.

Calculating Distances, Areas and Gradients

These calculations help us understand the real-world dimensions of features shown on the map.

📏 Measuring Distance

To measure a straight-line distance:

Use a ruler to measure the distance in centimetres
Multiply by the scale to convert to real-world distance
Example: 4cm on a 1:50,000 map = 4 × 0.5 = 2km

For curved lines (like roads or rivers), use a piece of string or a paper edge to follow the curve, then measure it.

📊 Calculating Gradient

Gradient shows how steep a slope is:

Find the height difference (vertical distance)
Measure the horizontal distance
Divide height difference by horizontal distance
Express as a ratio, fraction, or percentage

Example: If a hill rises 50m over a horizontal distance of 500m, the gradient is 50/500 = 1/10 or 1:10 or 10%

Map Symbols and Features

Topographical maps use standardised symbols to represent different features. Learning these symbols is like learning the alphabet of map reading!

🏠 Human Features

Buildings (houses, churches, schools)
Transport networks (roads, railways, footpaths)
Boundaries (county lines, national parks)
Land use (farms, quarries, golf courses)

🌲 Physical Features

Water bodies (rivers, lakes, marshes)
Woodland and vegetation types
Coastal features (beaches, cliffs)
Relief features (hills, valleys)

📝 Map Key

Always check the map key (legend) to understand the specific symbols used. OS maps have standardised symbols, but they can vary slightly between different map series and scales.

Case Study Focus: Ordnance Survey Maps

The UK's Ordnance Survey (OS) produces some of the world's most detailed topographical maps. The most common scales are:

1:25,000 Explorer maps: Showing great detail, perfect for walkers (4cm = 1km)
1:50,000 Landranger maps: Less detailed but covering larger areas (2cm = 1km)

OS maps use a specific grid system called the National Grid, dividing the UK into 100km squares identified by two letters (e.g., TQ for parts of London). This is why complete OS grid references start with two letters followed by numbers.

Practical Map Skills

Being able to use topographical maps effectively requires practice. Here are some key skills to develop:

🔎 Map Interpretation

Look for patterns and relationships between features:

Why are settlements located where they are?
How does relief influence transport routes?
What evidence of economic activities can you see?
How do physical features affect human activities?

👥 Cross-Sections

A cross-section shows the profile of the land along a line:

Draw a straight line on the map
Note where contour lines cross your line and their heights
Plot these heights on graph paper
Connect the points to show the land profile

Exam Tips for Topographical Map Questions

In your iGCSE Geography exam, you'll likely face questions requiring you to interpret topographical maps. Here are some tips:

Practice using grid references until they become second nature
Learn to quickly identify landforms from contour patterns
Be prepared to describe the distribution of features (using compass directions and distances)
Look for relationships between physical features and human activities
Use proper geographical terminology in your answers
Always include evidence from the map to support your points

Quick Revision Checklist

Make sure you can:

Use 4-figure and 6-figure grid references
Measure distances using the scale
Calculate gradients between points
Identify landforms from contour patterns
Recognise common map symbols
Describe the distribution of features using compass directions
Explain relationships between physical and human features

🧠 Test Your Knowledge!