Key Stage 3 geography · Geographical skills and fieldwork

KS3 thematic maps and satellite images: parent guide

Thematic maps, aerial photographs and satellite images are three of the main sources geographers use to see patterns across space. In Key Stage 3, students learn to recognise the different types, to describe what they show using evidence, and to judge how reliable each source is. The core skill is interpretation: moving from what can be seen to what it might mean, and being honest about what the source cannot show.

Thematic maps and satellite images, explained

A topographic map such as an Ordnance Survey map shows what is on the ground. A thematic map shows one theme, such as population, rainfall, income or land use, by shading, symbols or lines. Choropleth maps colour areas by value, with darker shades normally meaning higher values. Proportional symbol maps use circles whose size matches the amount. Dot maps place one dot for a set number of people or things. Isoline maps join places of equal value, as contours do for height and isobars do for air pressure. Flow-line maps use arrows or lines of different thickness to show movement, such as migration or trade.

Students are taught a simple routine for reading any thematic map: check the title, the key and the date; describe the overall pattern; pick out highest and lowest values and any anomalies; then suggest reasons. Good descriptions use place names and directions (“the highest densities are in the south-east, around the capital”) and numbers from the key. They also avoid saying more than the map shows. For example, a choropleth shows averages across a whole area, so it cannot reveal what is happening in a single village within it.

Aerial photographs are taken from aircraft or drones. A vertical photograph looks straight down and, like a map, shows the pattern of fields, roads and buildings. An oblique photograph is taken at an angle, so you can see the height of buildings and hills. Satellite images are taken from orbit, so they cover large areas and can be repeated over the years, which makes them excellent for showing change. Some are in natural colour, others in false colour, where invisible light, such as infrared, is shown in visible colours so that healthy plants or water stand out.

In class students describe what the image shows (land use, shapes, patterns, scale), then infer what has happened or why it is there, and finally evaluate the source. Photographs show real places at one moment, but they have no labels, they may be affected by cloud or shadow, and fine detail can be hard to make out. Because they have no key, students use clues such as shape, colour and texture: regular grids suggest planned streets or crop fields, dark green may mean woodland, and straight lines are usually roads or railways.

Students are expected to use these sources alongside one another and alongside other data, which is the “analysing and interpreting different data sources” skill. A thematic map suggests that something is happening; a satellite image or an OS map helps to explain why. Schools pick their own contexts, so your teenager might compare a satellite image of a delta, a city or a glacier at different dates, or a map of rainfall alongside one of relief. These skills are also used in geography fieldwork and in GCSE exam questions about unfamiliar data.

Words your child will hear

Thematic map: A map that shows a single topic or theme, such as population density or rainfall.
Choropleth map: A map that shades areas according to a value, with darker shades usually showing higher values.
Isoline: A line joining places with the same value, such as a contour for height or an isobar for pressure.
Vertical aerial photograph: A photograph taken looking straight down from above, like a map.
Oblique photograph: A photograph taken at an angle, showing the height and sides of features.
Satellite image: A picture of the Earth taken from a satellite in orbit.
False colour: An image in which colours are assigned to types of light so that features stand out, not as the eye would see them.

What the National Curriculum says

The programme of study for Key Stage 3 says:

Pupils should be taught to interpret Ordnance Survey maps in the classroom and the field, including using grid references and scale, topographical and other thematic mapping, and aerial and satellite photographs
Pupils should develop greater competence in using geographical knowledge, approaches and concepts [such as models and theories] and geographical skills in analysing and interpreting different data sources.

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

A model answer: describing and explaining a pattern

A choropleth map of an imaginary country shows population density in five bands: under 10, 10–50, 50–200, 200–500 and over 500 people per km². The darkest shade (the highest density) covers a small area in the south-east around the capital. Medium shades follow the main river valley. The palest shade covers the mountainous north. Describe the pattern, suggest reasons and say how you could check them.

Check the basics first. Read the title, find the key and note the units, here the number of people per square kilometre. Confirm that darker means denser.
Describe the pattern in order, with places and numbers from the key. The highest densities, over 500 people per km², are in a small area in the south-east around the capital. Medium densities follow the river valley. The lowest densities, under 10 people per km², are in the north, where the mountains are.
Suggest reasons, linking each to evidence. Capitals attract jobs and services, so people move in. River valleys usually have flat land, fertile soil and water supplies, which favour farming and settlements. Mountains are steep, cold and hard to build on, so fewer people live there.
Say how you could check. A satellite image of the south-east would show whether the land is built up; a physical map would show whether the north is high ground; a transport map would show whether roads and railways follow the river.
Finish with a limitation. The shading shows averages for each area, so a medium-density area may include both a dense town and empty farmland. A map with smaller areas, or a dot map, would show more detail.

Population is concentrated in the south-east around the capital, at over 500 people per km², and along the river valley, while the mountainous north is sparsely populated. Likely reasons are jobs in the capital, farmland and flat land in the valley, and harsh, steep terrain in the mountains. A satellite image and a physical map could confirm this, but a choropleth map shows only averages, so it hides variation within each area.

Common mistakes and how to help

Reading a choropleth map as showing exactly what is in every part of an area

The colour fills the whole area, so it looks as though everywhere inside it is the same.

What helps: Remind your teenager that each colour is an average. Ask: “What could be in this area that the colour hides?”

Describing a map without using data or place names

“It is darker in some places” feels like a description but gives no evidence.

What helps: Practise sentences with a place, a direction and a number: “Density is over 500 people per km² in the south-east.” Compare it with a vague version to see the difference.

Treating a satellite image as a map with labels

Digital maps often overlay names on satellite pictures, so they feel the same.

What helps: A raw image has no key. Ask what each shape, colour and texture suggests, and what is uncertain. False-colour images need a note of what colours represent.

Assuming a source shows the whole truth because it is a photograph

Photographs look objective and detailed.

What helps: Ask when it was taken, what the weather and season were, what it cannot show, and whether another source disagrees. Evaluating a source is a skill teachers reward, at KS3 and at GCSE.

How to help at home

Compare two views of the same place. Look at a street map and an aerial or satellite view of your area. Ask your teenager what each helps with, what each hides and how they would find the school, park or main road in each.
Spot change over time. If you have older photographs, or can look at digital maps from different years, find what has changed nearby: new estates, a bypass, felled woodland. Ask what caused it.
Make a family thematic map. Draw a plan of the house or street and shade it by something measurable, such as noise, number of plants or time spent in each room. It shows how a theme becomes a map and why choices of colour and classes matter.
Read the weather map. Weather maps use isolines and symbols. Check the forecast together and describe where it will be warmest and wettest, using the key, before looking at the text forecast.
Practise describing with evidence. When a map or chart appears in the news, ask for a two-sentence description with a place, a direction and a number, then a reason and a limitation. Short and regular is better than long and rare.

Builds on

Key Stage 2: Atlases, globes and digital maps
Key Stage 2: Compass points and grid references
Key Stage 2: Ordnance Survey map symbols
Key Stage 2: Fieldwork: observe and measure
Key Stage 2: Fieldwork: presenting findings