What you'll learn
- How to choose the best graph, chart or map for different types of geographical data.
- How to construct common graphs using sensible scales, axes and keys.
- How to read maps such as choropleth, isoline, dot and flow-line maps.
- How to extract patterns, trends, anomalies and comparisons from graphs and maps.
Why graphical skills matter
Geography is full of data: rainfall in mm, population in millions, GNI per head in US$, traffic counts, river velocity, migration flows, and many more. Graphical skills help you turn those numbers into patterns you can actually see.
Graphical representation
A graphical representation is any visual way of showing data, such as a graph, chart, diagram or map.
In GCSE Geography, these skills are assessed across all three papers, so you might use them in physical geography, human geography or fieldwork.
Starting point: data, variables and scales
Data and variables
Data are pieces of information collected through measurement, counting or research. A variable is something that can change, such as rainfall, population density, age, distance from the CBD, or river depth.
Some data are categorical: they are groups or labels, such as land use types or employment sectors. Other data are continuous: they can take many numerical values, such as temperature, height, distance or time.
Scale
A scale is the set of values used on an axis, key or map. A good scale uses most of the space available and goes up in even, easy-to-read intervals.
For example, if your highest rainfall value is 92 mm, a vertical axis from 0 to 100 mm in intervals of 10 mm would be sensible. An axis from 0 to 1000 mm would waste space and make the pattern hard to see.
Choosing a scale
Use simple intervals such as 1, 2, 5, 10, 20, 50 or 100. Avoid awkward intervals like 7 or 13 unless the graph paper forces it.
Choosing the right graph or chart
Different graphs are useful for different jobs. The first decision is: what kind of data are you showing, and what pattern do you want to reveal?
Common choices
| Data or purpose | Suitable graph or chart | Why it works |
|---|---|---|
| Change over time | Line chart | Shows trends, rises and falls clearly |
| Separate categories | Bar chart | Makes categories easy to compare |
| Proportions of a total | Pie chart or divided bar | Shows how a whole is split into parts |
| Simple counts using symbols | Pictogram | Useful for simple visual comparisons |
| Continuous data in equal class intervals | Histogram | Shows frequency distribution |
| Relationship between two variables | Scattergraph | Shows correlation and anomalies |
| Age and sex structure | Population pyramid | Shows population structure |
| Spatial pattern across areas | Choropleth map | Shows variation by area |
| Movement between places | Flow-line map | Shows direction and volume of movement |
Choosing a suitable graph
- Monthly average temperature for a UK city is time-based data, so a line chart is suitable because it shows change through the year.
- Land use categories in a town centre are categorical data, so a bar chart is suitable if you want to compare the categories.
- Percentages of energy use from coal, gas, nuclear and renewables are parts of a whole, so a pie chart or divided bar is suitable.
- Distance from the city centre and land value are two numerical variables, so a scattergraph is suitable because it can show whether a relationship exists.
Constructing graphs accurately
Line charts
A line chart shows change, usually over time. The horizontal axis often shows time, and the vertical axis shows the measured variable.
Use line charts for things like temperature over a year, river discharge during a storm, or changes in population over decades.
Bar charts
A bar chart compares categories. The bars should be the same width, and there should usually be gaps between them because the categories are separate.
For example, you might compare employment in primary, secondary, tertiary and quaternary sectors for the UK or Nigeria.
Pie charts and divided bars
A pie chart shows proportions as sectors of a circle. A divided bar shows proportions as sections of one bar, often out of 100%.
To draw a pie chart from raw data, convert each category into an angle:
sector angle=category valuetotal value×360∘\text{sector angle} = \frac{\text{category value}}{\text{total value}} \times 360^\circsector angle=total valuecategory value×360∘Drawing pie chart sectors
A fieldwork survey records 40 land-use sites: 18 residential, 12 services, 6 industrial and 4 green space.
- Calculate the angle for residential land use:
- Calculate the angle for services:
- Calculate the angle for industrial land use:
- Calculate the angle for green space:
- Check the sectors add to 360°: 162° + 108° + 54° + 36° = 360°.
Pictograms
A pictogram uses repeated symbols to represent values. For example, one symbol might represent 10 tourists or 100 houses.
The key is essential. If one symbol equals 10 people, then half a symbol equals 5 people.
Histograms with equal class intervals
A histogram shows continuous data grouped into classes, such as pebble size from 0–2 cm, 2–4 cm, 4–6 cm and 6–8 cm.
Class interval
A class interval is a range of values used to group data, such as 0–10 mm or 10–20 mm.
In GCSE Geography, histograms usually use equal class intervals. This means the bars can be drawn with frequency as the height, and the bars should touch because the data are continuous.
Bar chart or histogram?
A bar chart has gaps because it compares separate categories. A histogram has touching bars because it shows continuous numerical data grouped into intervals.
Scattergraphs
A scattergraph plots pairs of data to see whether two variables are related. Each point represents one pair of values.
For example, you might plot distance from the CBD against land value, or river distance downstream against channel width.
Correlation
Correlation is the relationship between two variables. Positive correlation means both increase together. Negative correlation means one increases as the other decreases. No correlation means there is no clear relationship.
A line of best fit is a line drawn through the general pattern of points. It should have roughly equal numbers of points on either side, ignoring clear anomalies.
Interpreting a scattergraph
A scattergraph shows distance from the CBD on the x-axis and land value on the y-axis.
- Points close to the CBD have high land values, while points further away have lower land values.
- The overall pattern slopes downwards from left to right, so the graph shows negative correlation.
- One point far from the CBD has a high land value, so it may be an anomaly, perhaps caused by a shopping centre, transport hub or luxury housing area.
Population pyramids
A population pyramid is a back-to-back bar chart showing population by age group and sex. Males are usually shown on the left, females on the right, and age groups run from youngest at the bottom to oldest at the top.
A wide base often suggests a high birth rate and a youthful population. A narrow top suggests fewer elderly people and possibly lower life expectancy. A more rectangular or top-heavy shape, such as in Japan, suggests an ageing population. A youthful pyramid, such as in Nigeria, usually has a wider base. Exact shapes depend on the year and data source.
Reading population pyramids
Start with the base, then the working-age middle, then the top. This helps you comment on birth rate, dependency and life expectancy.
Completing and reading maps
Some geographical data are best shown on maps because location matters.
Choropleth maps
A choropleth map shades areas according to value. For example, it could show population density by county, GNI per head by country, or deprivation by local authority.
Use a clear key with ordered shading, usually from light for low values to dark for high values.
Using raw totals on choropleth maps
Choropleth maps work best with rates, percentages or densities. Raw totals can mislead because larger areas often have larger totals simply because they are bigger.
Isoline maps
An isoline map uses lines to join places with the same value. A contour line is an isoline joining points of equal height. Other examples include isobars for air pressure and isohyets for rainfall.
Gradient
Gradient means how quickly a value changes over distance. On an isoline map, lines close together show a steep gradient; lines far apart show a gentle gradient.
You also need to understand value on isoline maps. If a point lies between the 200 m and 300 m contours, its height is between 200 m and 300 m.
Calculating gradient from contours
Two contour lines are labelled 100 m and 200 m. The map distance between them represents 500 m on the ground.
- Find the change in height: 200 m − 100 m = 100 m.
- Use the gradient idea:
- Substitute the values:
- Interpret the result: the height changes by 0.2 m for every 1 m horizontally, which is a steep slope.
Dot maps, dot lines and proportional symbols
A dot map uses dots to show quantity or distribution. For example, one dot might represent 100 farms or 1000 people. Dot maps are good for showing clustering.
A dot line uses dots or marks along a route, line or transect to show how something varies along it. In fieldwork, this could show litter counts or pedestrian flow along a street.
A proportional symbol map uses symbols that change size according to value. For example, larger circles might show larger city populations.
Proportional symbol sizing
On proportional symbol maps, the area of the symbol should represent the value, not just the radius. If you are only interpreting the map, use the key rather than guessing by eye.
Flow-line maps
A flow-line map shows movement between places. The line or arrow direction shows where something moves, and the line width usually shows how much moves.
Examples include migration flows into the UK, commuter flows into London, trade flows, or water transfers.
Plotting when axes and scales are provided
Sometimes the axes and scales are already drawn, and your job is to complete the graph.
Axis
An axis is a reference line on a graph. The x-axis is usually horizontal, and the y-axis is usually vertical.
For a point on a scattergraph, the x-value tells you how far to move across, and the y-value tells you how far to move up.
Plotting a point on given axes
A scattergraph uses distance from the sea on the x-axis and average annual rainfall on the y-axis. You need to plot a place 30 km from the sea with 850 mm of rainfall.
- Use the x-axis scale to locate 30 km from the sea.
- From that position, move vertically until you reach 850 mm on the y-axis scale.
- Place the point where the 30 km position and 850 mm value meet.
Interpreting and extracting information
When you read any graph, chart or map, aim to extract evidence, not vague impressions.
Useful things to look for include:
- Highest and lowest values
- Overall trend, such as increase, decrease or fluctuation
- Clusters, where many values are close together
- Anomalies, which do not fit the main pattern
- Comparisons, using numbers and units
- Spatial pattern, such as north–south divide, coastal concentration or urban clustering
Dispersion graphs
A dispersion graph shows how spread out values are along a scale. It is useful for seeing range, clustering and outliers. For example, you might use one to show pebble sizes on different beaches or environmental quality scores at different sites.
Range
The range is the difference between the highest and lowest value. It is a simple measure of spread.
Interpreting a dispersion graph
A dispersion graph shows environmental quality scores from −5 to +5 for two streets. Street A has scores from −1 to +5, while Street B has scores from −4 to +2.
- Compare the highest values: Street A reaches +5, while Street B reaches only +2.
- Compare the lowest values: Street A falls to −1, while Street B falls to −4.
- Compare overall spread: Street A has a range of 6, and Street B also has a range of 6.
- Make a geographical judgement: Street A appears to have better environmental quality overall because its scores are generally higher.
In the exam
- Match the graph to the data: time needs a line chart, categories need bars, proportions need pie charts or divided bars, and relationships need scattergraphs.
- Always use evidence when interpreting: quote values, units and place names from the graph or map.
- Check the key, scale and axes before answering, especially on choropleth, isoline and flow-line maps.
- Describe the pattern first, then explain possible reasons using geographical understanding.
Check yourself
- Which graph would you choose to show the relationship between distance downstream and river velocity?
- On an isoline map, what does it mean when lines are very close together?
- Why can raw totals be misleading on a choropleth map?
