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GIS and Image Skills » Photographs, Satellite Images and GIS

What you'll learn this session

Study time: 30 minutes

Cambridge spec: Geographical skills, GIS and image skills

Read and describe photographs, satellite images, cartoons and diagrams
Spot bias in written sources
Suggest improvements to, and reasons for using, maps, graphs and photos
Explain what GIS is, and its benefits and limitations

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Reading visual images

Exam papers often show a source and ask you to deconstruct it. That means taking it apart, looking carefully, then saying what it shows, what it means and how reliable it is.

Key terms:

Ground-level photograph: taken by someone standing on the ground, so it shows things at human height.
Vertical aerial photograph: taken from directly above, looking straight down, a bit like a map.
Oblique aerial photograph: taken from above at an angle, so you see the sides of things and the horizon.
Satellite image: a picture of the Earth taken from space, often covering a large area.

How to describe and annotate a photo

Do not just list objects. Work through the photo in order:

Foreground: the part nearest the camera, at the bottom of the photo.
Middle ground: the centre of the photo.
Background: the furthest part, at the top, including the sky or hills.

In each part, pick out physical features (natural things such as rivers, slopes, vegetation, cliffs) and human features (things people built or did, such as roads, houses, farms, bridges).

📷 Ground-level

Good for detail: the type of building, the plants, the condition of a path. Poor for showing the whole area, because things in front block the view.

🛰 Aerial and satellite

Good for patterns and the big picture: the shape of a settlement, field layout, the course of a river. Poor for detail and height. Vertical images make tall things hard to judge.

To annotate, add short labels with arrows. A good label says what it is and adds a fact, for example "terraced fields: steep slope farmed using steps".

Cartoons, pictures and diagrams

A cartoon makes a point, often with humour. Ask: What is shown? What do the symbols stand for? What is the cartoonist's opinion? Remember it is one view, not a fact. A diagram simplifies a process, so use its labels and arrows to describe what happens.

Written sources and bias

A source can be a newspaper article, a leaflet, a speech or a web page. Bias means showing only one side, or showing it unfairly. To spot it, ask three questions:

Who wrote it? A mining company and a local campaign group will tell the same story differently.
Why was it written? To inform, to persuade, to sell or to raise money?
What is left out? Are costs, risks or other groups missing?

Watch for emotive words such as "disaster" or "miracle", and for opinions written as if they were facts.

Improvements, issues and reasons for using sources

You may be asked to suggest why a map, graph, photo or statistic was used, or what is wrong with it. Think about:

Reasons for using it: a photo shows what a place looks like, a graph shows a trend quickly, a map shows where.
Issues: the photo may show only one day or one angle, the graph may leave out years, the sample may be too small.
Improvements: take photos at different times, add a scale, use more data, add a key.

What is GIS?

GIS (geographic information system) is computer software that stores data as layers on a digital map. Each layer shows one type of information, such as roads, rivers, population, flood zones or land use. You can switch layers on and off and lay one over another.

🗺 Using GIS

Switch on the layers you need and look for trends and patterns. For example, lay a river-flood layer over a housing layer to see which homes are at risk. That shows an issue, and helps to solve a problem, such as where to build a new flood wall.

🔎 Exam approach

Name the layers, say what pattern the overlap shows, then say what decision it helps with. Do not just say "GIS shows everything".

Benefits and limitations of GIS

✅ Benefits

Combines many types of data in one place
Quickly shows patterns that are hard to see in tables
Easy to update and to share with many people
Helps planners test ideas before spending money

❌ Limitations

Software and training are expensive, especially for poorer places
Needs up-to-date data, and old data gives wrong answers
Results are only as good as the data put in
Some data is missing or not available for remote places

Worked example

A photo (made up) shows a coastal town. In the foreground is a sandy beach with a sea wall. In the middle ground are hotels and a road. In the background are steep green hills. A good answer says: "In the foreground there is a sandy beach, a physical feature, protected by a concrete sea wall, a human feature. In the background, steep wooded hills limit where the town can grow."

Common mistakes

Listing objects with no order. Saying a photo "proves" something when it shows one place at one moment. Calling a source biased with no reason. Writing that GIS "is a map" when it is layers of data.

Exam-style question

Fig. 1.1 is a made-up oblique aerial photograph of a river town. It shows a river, with houses on both banks, a bridge, farmland behind the town and wooded hills in the distance.

(a) Identify one human feature and one physical feature shown in Fig. 1.1. [2 marks]

(b) Suggest one reason why a vertical aerial photo might be better than a ground-level photo for planning flood defences. [2 marks]

Model answer

(a) Human: the bridge (1). Physical: the river or the wooded hills (1).

(b) A vertical photo looks straight down so it shows the whole river and the shape of the floodplain (1), while a ground-level photo only shows a small part, partly blocked by buildings (1).

(c) A benefit is that GIS puts layers such as the river, ground height and housing on one map (1), so planners can see which homes are at risk of flooding (1). It lets them test where a flood wall would protect most people before spending money (1). A limitation is that it needs up-to-date data, and old flood records could give wrong results (1). It also needs expensive software and trained staff (1). Overall GIS is very useful for planning, as long as the data is accurate and the council can afford it (1).

Exam tip

For an "Assess" question, give both benefits and limitations and finish with a short judgement, as in part (c).

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