What mistakes do students make with Graphical skills?

Assuming the subdivisions between major logarithmic intervals (e.g., between 10 and 100) are equally spaced. Recognise that subdivisions get progressively closer together as the value approaches the next power of ten. Reading a value halfway between 10 and 100 as 55. Understand that the midpoint on a logarithmic scale represents a geometric mean, so the physical halfway point is closer to 31.6, and the line for 50 is further up the axis. Attempting to plot zero or negative values on a standard logarithmic scale. The logarithm of zero is undefined; logarithmic scales typically start at a...

What are the exam tips for Graphical skills in Geography AQA A-Level?

Always check the axis labels carefully to determine if the scale is base-10 logarithmic before reading any data points. When plotting points, use the minor grid lines carefully, remembering they represent 20, 30, 40 etc., not linear increments. Use a clear ruler to trace across from the axis to the data point to avoid misreading the non-linear subdivisions.

AQA · A-Level · Geography

Course version: 7037 · Version from Sept 2018

Graphical skills: Graphs with logarithmic scales.

Logarithmic scales are essential in geography for plotting data that spans several orders of magnitude on a single axis.

Checked against the AQA 7037 specification (opens in a new tab) on 10 November 2026.

Point 6 of 7

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

Identify when a logarithmic scale is appropriate, such as when data spans multiple orders of magnitude.
Accurately read values from a logarithmic axis, noting the unequal spacing of subdivisions between major intervals.
Plot data points correctly on semi-logarithmic or log-log graphs, such as the Hjulström curve or flood frequency graphs.
Interpret relationships with the graph type stated: a straight line on a semi-log plot with a logarithmic y-axis can indicate exponential change, while a straight line on a log-log plot indicates a power relationship.

Common mistakes and how to put them right

Assuming the subdivisions between major logarithmic intervals (e.g., between 10 and 100) are equally spaced.
Put it right: Recognise that subdivisions get progressively closer together as the value approaches the next power of ten.
Reading a value halfway between 10 and 100 as 55.
Put it right: Understand that the midpoint on a logarithmic scale represents a geometric mean, so the physical halfway point is closer to 31.6, and the line for 50 is further up the axis.
Attempting to plot zero or negative values on a standard logarithmic scale.
Put it right: The logarithm of zero is undefined; logarithmic scales typically start at a small positive number like 0.1 or 1.

Exam tips

Always check the axis labels carefully to determine if the scale is base-10 logarithmic before reading any data points.
When plotting points, use the minor grid lines carefully, remembering they represent 20, 30, 40 etc., not linear increments.
Use a clear ruler to trace across from the axis to the data point to avoid misreading the non-linear subdivisions.

Try the lesson

The start of the Graphical skills: Graphs with logarithmic scales. lesson, made from checked teaching notes for this specification point.

Have a go first

Which of the following best describes the primary advantage of using a logarithmic scale on a graph in geographical data presentation?

Tip: press 1 to 4 to choose

Listen

Logarithmic scales are essential in geography for plotting data that spans several orders of magnitude on a single axis. Unlike linear scales, where each interval represents a constant addition, each major interval on a base-10 logarithmic scale represents a multiplication by ten (for example, 1, 10, 100, 1000). This prevents small values from being compressed and unreadable when plotted alongside extremely large values. A classic geographical application is the Hjulström curve, which uses logarithmic scales for particle size (in mm) and water velocity (in cm s⁻¹) to show the relationship between river flow and sediment transport. A strong answer earns marks for these points. Identify when a logarithmic scale is appropriate, such as when data spans multiple orders of magnitude. Accurately read values from a logarithmic axis, noting the unequal spacing of subdivisions between major intervals. Plot data points correctly on semi-logarithmic or log-log graphs, such as the Hjulström curve or flood frequency graphs. Interpret relationships with the graph type stated: a straight line on a semi-log plot with a logarithmic y-axis can indicate exponential change, while a straight line on a log-log plot indicates a power relationship. A common slip: Assuming the subdivisions between major logarithmic intervals (e.g., between 10 and 100) are equally spaced. Instead, Recognise that subdivisions get progressively closer together as the value approaches the next power of ten. Exam tip: Always check the axis labels carefully to determine if the scale is base-10 logarithmic before reading any data points.

See it

A top-down flowchart. The first box reads 'Data spans several orders of magnitude' and points to 'Use a base-10 logarithmic scale'. From that box four branches lead out. The first goes to 'Each major interval is a multiplication by ten', which leads to 'Small values are not compressed'. The second goes to 'Subdivisions get closer together towards the next power of ten', which leads to 'Read values carefully from the non-linear subdivisions'. The third goes to 'Semi-log plot: straight line indicates exponential change'. The fourth goes to 'Log-log plot: straight line indicates a power relationship'. A fifth branch from the logarithmic scale box goes to 'Cannot plot zero or negative values'. — It shows when a logarithmic scale is appropriate, how its intervals and subdivisions behave, what a straight line indicates on semi-log and log-log plots, and that zero or negative values cannot be plotted.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The first box reads 'Data spans several orders of magnitude' and points to 'Use a base-10 logarithmic scale'. From that box four branches lead out. The first goes to 'Each major interval is a multiplication by ten', which leads to 'Small values are not compressed'. The second goes to 'Subdivisions get closer together towards the next power of ten', which leads to 'Read values carefully from the non-linear subdivisions'. The third goes to 'Semi-log plot: straight line indicates exponential change'. The fourth goes to 'Log-log plot: straight line indicates a power relationship'. A fifth branch from the logarithmic scale box goes to 'Cannot plot zero or negative values'.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

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