Visualizing Topographic Maps and Lines of Contour

Contour lines on maps represent lines of constant height, and all points on a line = same height. Contour lines show 3D information on 2D representations Topo. maps show changes in height and where the terrain is steep or flat. Contour lines at different heights cannot cross each other.

Contour lines are lines of constant height

All the points on a given contour line are all at the same height. If they move from one contour line to another then there is a change of height. The closer the lines are the ‘faster’ the height changes, and thus the ‘steeper’ the terrain. The further apart the contour lines are, the greater distance over which height changes = gentler slope.

Activity 1: Potato Mountains

Draw all the contour lines. View the potato from the side and above. The side view from shows that all the lines are parallel and equidistant. The top view shows the steep sides have contour lines that are close together. Gentle slopes occur when the contour lines are further apart.

What is seen from above is what is drawn on a map: each contour line we see comprises all the points that are a certain height above some base level (usually sea level). Going from one contour line to another contour line involves a change of height.

 Slice the potatoe along the contour lines. Poke a hole down through the potato from the summit to the base, to help with the alignment. Trace around each piece on a paper, using the hole to line up successive pieces over the one spot. The result will be a contour map of the potato. How does the contour lines show the varying steepness of the potato mountain?

Activity 2: Model it

Build a model using the template in ContourModel (PDF - 420Kb). Cut right around one of the contour lines and keep the resulting piece. Repeat this for a different contour line on each of the other copies. Assemble all your pieces to make a model.

Use this model ContourProfiles (PDF - 423Kb) to visualise different views of the terrain determined by the contour lines.

 Activity 3: Match the Views

'Match the View' (PDF - 455Kb) gives 5 contour maps & 5 profiles. Match the pairs.

Answers: 1 = D (very tall peak to the right of centre), 2 = A (much taller peak on left), 3 = E (the lowest mountain with only 4 contour lines), 4 = B, 5 = C (gentle slope to the right of the main peak before dropping sharply).

Activity 4: Imaginary Bushwalks

 Track 1. The walk begins heading south-east, through wooded bushland, rising slowly for about 4 km until a steep climb over about 1.5km brings you to a viewpoint on a ridge. Turning west, you head down steeply for about 2 km (maybe to a creek), and then climb back up for 1.5 km to the second view point. You then bear south for 2 km along a level section just below a ridge on the left. Then you climb up and over the side of a hill in about 2.5 km, dropping into a saddle between two peaks. Here you turn north-east, climb to the top of the peak which now appears ahead of you (the summit is reached after 1.5 km) and after climbing down, enjoy walking down a final gentle slope for another 5 km.

 Track 2. Head north and north east up a very steep track leading to the rim of the crater and proceed inside. The centre of the crater is reached after 3 km from your start where you can enjoy a short break. Take the steep track to the east, out of the crater and down the other side (for about 1.5km). Head on a level path along the saddle between the crater peak and the smaller peak on your right, and continue walking around the second mountain for about 10 km, before the track turns east and drops steadily to your next campground.