A cross-section is a side view of the land along a line. Set the horizontal axis to match the line, choose an even vertical scale, plot each height, then join the points. It appears when a question supplies heights along a transect or map line and asks for a drawn profile.
This lesson uses ideas from gradient and contour reading in scale, distance and relief.
How do you draw a cross-section, step by step?
- Draw the horizontal axis the same length as the line on the map, and mark each supplied position.
- Choose the vertical scale so the tallest height fits the grid, with equal steps. Label the axis with heights.
- Plot each point at its horizontal position and calculated vertical height.
- Join the points with a smooth line and label the highest and lowest points.
- Give a title that names the line, for example “Cross-section from A to B”.
Worked example
The data are invented for practice. A line from A to B is 8 cm long on a 1:25 000 map. Heights are supplied every 2 cm.
| Distance from A (cm) | 0 | 2 | 4 | 6 | 8 |
|---|---|---|---|---|---|
| Height (m) | 60 | 80 | 120 | 100 | 60 |
Horizontal axis: 8 cm long, marked at 0, 2, 4, 6 and 8 cm.
Vertical scale: start the axis at 40 m. Let 1 cm stand for 20 m. Heights above the start are 60 − 40 = 20, 80 − 40 = 40, 120 − 40 = 80, 100 − 40 = 60 and 60 − 40 = 20 m.
Plot heights: 20 ÷ 20 = 1 cm, 40 ÷ 20 = 2 cm, 80 ÷ 20 = 4 cm, 60 ÷ 20 = 3 cm and 1 cm. The peak is at 4 cm along, at 4 cm above the axis start.
Vertical exaggeration: across, 1 cm is 250 m. Up, 1 cm is 20 m. The exaggeration is 250 ÷ 20 = 12.5 times.
The mistake to watch for
Mistaken plot: the student plots every height as if 1 mm stood for 1 m, so 120 m goes 12 cm above the axis.
The vertical axis has no planned scale, so the section does not fit the page and the shape is wrong.
The correction is to decide the vertical scale first, then convert each height. Check the highest point fits on the grid before plotting the rest.
A second slip is to extend the line past the last supplied point. The section ends where the data end.
Check yourself
1. Heights along a line are 30 m, 50 m and 90 m. The vertical axis starts at 0 m, and 1 cm stands for 10 m. How high above the axis is each point?
Show answer
30 ÷ 10 = 3 cm, 50 ÷ 10 = 5 cm, 90 ÷ 10 = 9 cm.
2. The horizontal scale is 1 cm to 100 m and the vertical scale is 1 cm to 10 m. Find the vertical exaggeration.
Show answer
100 ÷ 10 = 10 times.
3. The axis starts at 40 m and 1 cm stands for 20 m. How high above the axis is a point at 75 m?
Show answer
75 − 40 = 35 m, and 35 ÷ 20 = 1.75 cm.
Where this leads next
Test the whole module in the scale and relief practice set, and revisit reading contours if the heights feel unfamiliar. The map scale, contour and gradient practice tool and the statistics and distribution explorer give extra drills.
If your cross-sections keep coming out the wrong shape, a teacher in online one-to-one Geography tuition can check your scale choices as you draw.