Cartographic Skills » OS Maps: Relief and Reading the Landscape

Showing height on a map

An OS map is flat, but the land is not. Mapmakers show height in two main ways. Remember, relief means the height and shape of the land. This lesson shows you how to read it.

Key terms:

• Contour line: a thin brown line that joins places of the same height above sea level.
• Spot height: a black dot with a number beside it, giving the exact height of one point in metres.
• Gradient: how steep a slope is.
• Cross section: a drawing of the height of the land along a line, as if the land was sliced open and viewed from the side.

Contour lines

Contour lines are drawn at regular height steps. This step is called the contour interval. On a 1:50 000 map it is normally 10 metres. On a 1:25 000 map it is normally 5 metres. Every fifth line is thicker and has its height written on it.

To tell which way a slope goes, look at the numbers on the lines. The numbers get bigger as you go uphill. Spot heights help here. A spot height of 214 beside a ring of contours tells you that the middle is the top of a hill.

Gradient

Gradient compares how far you go up with how far you go along. Use this method:

• Find the height difference between two points (vertical distance).
• Measure the distance between them on the map and use the scale (horizontal distance).
• Divide the vertical distance by the horizontal distance. Use the same units for both.

Major relief features

Different patterns of contour lines make different shapes. Learn these five.

Cross sections and relief

A cross section turns contour lines into a side view. To draw one:

• Lay the edge of a strip of paper along the line you want to draw.
• Mark every contour the line crosses and write its height.
• Place the paper along the bottom of a graph with a height scale.
• Plot a cross at each height and join them with a smooth line.

The steep parts of the cross section match places where contours are close together. A flat section matches widely spaced lines. Use this to name a feature. A drawing with a bowl shape and steep sides is a valley. A drawing with a flat top is a plateau.

A transect on a map is a line across the map along which you record what you find, such as land use or relief. A transect of a physical and human landscape might show a river, then fields, then houses, then a road.

Reading the physical and human landscape

You can use an OS map as evidence to make inferences. An inference is a conclusion drawn from clues. Always give the clue and then what it suggests.

• Relief: steep land with close contours is hard to build on or farm.
• Drainage: blue lines show streams and rivers. Where several join, the river grows. Many streams suggest wet land or heavy rainfall.
• Settlement: look at where buildings are. Villages often sit on flat land or beside a river crossing. Only a few farms suggests a quiet, thinly settled area.
• Communication: roads, railways and paths. A motorway with junctions shows good links. Narrow minor roads show a rural area.
• Land use: green symbols show woodland. Rough grassland or heath symbols with few buildings on high ground can show moorland or rough grazing. Buildings close together show a built-up area.

Coasts, rivers and glaciated land

On large scale maps you may be asked to describe the physical features of two landscapes. Here are the map clues for three.

When you describe them, use the names you know from the physical landscapes lessons. Give the map evidence too, for example the contour pattern or a grid reference.

Inferring human activity and tourism

Symbols show what people do. A map key lists them. Clues for tourism include:

• Camp sites and caravan sites (tent or caravan symbols).
• Car parks and picnic sites.
• Viewpoints, nature reserves and information centres.
• Public footpaths, long distance paths and youth hostels.
• Museums, castles and places of interest.

Other human activity can also be inferred. Quarries show that stone, sand or gravel is being dug out. Farms show farming. A railway station and many roads suggest a town that people travel to. The more tourist symbols in one area, the more likely it is to be popular with visitors.

Exam-style question

The map shows a hillside. A path climbs from a spot height of 120 m to the top of a hill at 220 m. The path is 2 km long on the map.

(a) Calculate the gradient of the path. Show your working. [2 marks]

(b) The contour lines close to the viewpoint are very close together. What does this tell you about the slope? [1 mark]

(c) Give two pieces of map evidence that the area is used for tourism. [2 marks]