Presenting Data: Maps and Spatial Techniques

Geography is fundamentally about place and space. While charts and graphs are excellent for showing numerical patterns, many geographical questions demand a spatial answer — you need to show where things happen, not just what happens. This lesson covers the map-based and spatial techniques you need to know for the Edexcel B exam, from choropleth maps to GIS.

These techniques are essential for fieldwork presentation and for interpreting resources in the exam. You may be asked to draw, describe, interpret or evaluate any of these spatial techniques.

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Choropleth Maps

A choropleth map uses shading or colour to show differences in a variable across defined areas (such as countries, regions or wards).

How to Draw a Choropleth Map

1. Obtain a base map divided into areas (e.g. electoral wards, countries, postcodes)
2. Gather data for each area (e.g. population density, average income, unemployment rate)
3. Divide the data into classes (typically 4–6 classes)
4. Assign a shade or colour to each class — darker shading represents higher values
5. Shade each area according to its data value
6. Add a key showing what each shade represents

Choosing Class Boundaries

Method	Description	When to Use
Equal intervals	Each class covers the same range (e.g. 0–10, 10–20, 20–30)	When data is evenly distributed
Quantiles	Each class contains the same number of areas	When you want equal representation in each class
Natural breaks	Classes are set at natural gaps in the data	When data has clear clusters

Advantages and Limitations

Advantages	Limitations
Shows spatial patterns clearly at a glance	Implies the whole area has a uniform value (rarely true)
Easy to compare areas	Class boundaries can change the visual impression significantly
Effective for large-scale patterns	Cannot show exact values — only which class an area falls into
Works well with census and statistical data	Areas of different sizes can be misleading (large rural areas dominate visually)

Exam Tip: When describing a choropleth map, use compass directions and place names to describe the spatial pattern. For example: "The highest unemployment rates are concentrated in the north-east of the region, particularly in wards around the former industrial areas, while southern suburban wards have the lowest rates."

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Isoline Maps

An isoline map uses lines to connect points of equal value. You are already familiar with some isoline maps — contour lines on an Ordnance Survey map connect points of equal height, and isobars on a weather map connect points of equal atmospheric pressure.

Common Types of Isolines

Isoline Type	Connects Points of Equal...	Example
Contour line	Height above sea level	OS maps, topographic maps
Isobar	Atmospheric pressure	Weather maps
Isotherm	Temperature	Climate maps
Isohyet	Rainfall	Precipitation maps

How to Draw an Isoline Map

1. Plot data points on a base map with their values
2. Decide on the interval between isolines (e.g. every 10 metres for contours)
3. Interpolate between points to estimate where each isoline should pass — if one point has a value of 8 and another has 14, the isoline for 10 would pass approximately 2/6 of the way between them
4. Draw smooth, flowing lines that never cross each other
5. Label each line with its value

Reading Isoline Maps

• Closely spaced isolines indicate a steep gradient (rapid change)
• Widely spaced isolines indicate a gentle gradient (slow change)
• Isolines that form concentric circles indicate a peak (high point) or a depression (low point)
• The values always increase in one direction and decrease in the other

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Flow Line Maps

A flow line map uses lines of varying width to show the direction and volume of movement between places.

How They Work

• The width of the line represents the quantity (e.g. number of people, tonnes of goods, vehicles per hour)
• The direction of the line shows the route of movement
• A scale is provided showing what each line width represents

Uses in Geography

Application	Example
Migration flows	Arrows showing migration between countries
Traffic flows	Lines showing vehicle counts on different roads
Trade flows	Lines showing exports between countries
Pedestrian movement	Lines showing footfall routes in a town centre

Advantages and Limitations

Advantages	Limitations
Shows both direction and volume of movement	Lines can overlap and become difficult to read
Very visual and easy to interpret	Does not show the exact route taken
Good for comparing flows between routes	Difficult to show many flows on one map
Effective for traffic and migration studies	Scale can be hard to judge precisely

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Proportional Symbol Maps

A proportional symbol map uses symbols (usually circles, but sometimes squares or other shapes) of varying size to represent data values at specific locations.

How to Draw a Proportional Symbol Map

1. Calculate the radius of each circle based on the data value — for proportional circles, the area of the circle should be proportional to the data value (area = π r²)
2. Plot circles at the correct locations on a base map
3. Include a scale showing the relationship between circle size and data value
4. Circles may overlap — draw the smallest on top for visibility

Advantages and Limitations