Mapping techniques
Some data is easier to understand when it is shown on a map. This is especially true of spatialRelating to space or how things are spread out., where spread of the information is important.
Choropleth maps
Choropleth maps show interval dataNumbers that are in order and that have fixed differences between the values. (data that is linked, rather than data from different categories) as colours. They are shaded in using one colour, where the darker shades represent high numbers and the lighter shades represent low numbers. A choropleth map needs a key to explain what the different shades mean. population densityThe average number of people in a certain area. can be shown using a choropleth map.
The world map above shows us that the most densely populated areas are western Europe, the north-east of the USA and coastal areas in eastern Asia such as China. The least populated areas (shown in yellow) are across the polar regions, through South America and central parts of Australia. North Africa and the Middle East are also sparsely populated regions of the world.
Isoline maps or synoptic charts
Isoline maps show lines that join up areas or values that are equal. atmospheric pressureThe weight of air resting on the Earth's surface. is shown using an isoline map. The areas of equal pressure are joined using a line, which helps people to see the position of high and low pressure systems.
The isoline map above shows there is a ridge of high pressure over northern Italy and a trough of low pressure off the coast of Scotland.
Dot maps
Dot maps show information as individual dots on a map. Each dot might represent more than one of something. Dot maps are often used to show population distributionThe location of people in an area..
Within the dot map it is possible to determine that most people live in western Europe, the north-east of the USA, and coastal areas in eastern Asia such as China. The least populated areas (shown in yellow) are across the polar regions, through South America and central parts of Australia and Asia.
Desire lines and flow lines
Desire and flow line maps show movements from one place to another:
- flow lines show the exact path of movement
- desire lines show a general direction of movement
Movements are shown as lines. Thick lines show high amounts of movement and thin lines show low amounts. tradeThe exchange of goods for money between producers and consumers. or migrationWhen people move from one place to another. patterns are often shown using desire or flow lines.
Interpreting the flow line map tells us that migrants to Britain come form three locations directly, the Caribbean, Uganda and India/Pakistan. It also tells us that people from the UK migrate to South Africa, Australia and New Zealand, and that these people travel furthest.
Proportional symbols
Proportional symbols can be added to a map to show differences between places. The same symbol appears larger or smaller, depending on how something changes. Proportional symbols on maps could be used to show the number of wind farmLand which contains a large group of wind turbines. within a country.
The single location which generates the most energy is off the eastern coast of Norfolk, England. However, there are multiple locations across Scotland which collectively produce the most electricity within the UK.