Cross-sections and transects

A video outlining how to construct a cross-section using a topographic map and grid paper. The difference between cross-sections and transects is outlined.

This video:

  • details how to construct a cross-section from a topographic map, beginning with finding two points of reference A and B and recording contour heights between the two points
  • demonstrates a completed cross-section and an example of a transect to provide an understanding of the key differences and similarities between each graph.

Watch 'Cross sections and transects' (2:53).

Learn about topographic cross sections and transects

[Music playing]

[Screen shows a blue sky with clouds. Text on screen reads, ‘Curriculum Secondary Learners – HSIE. Cross sections and transects. Presented by Melissa Ellis’.]

Melissa Ellis

In this episode, we're learning about topographic cross-sections and transects.

[Presenter is standing in front of a decorative background. In the bottom right-hand corner of the screen, the text reads, ‘Melissa Ellis. HSIE Curriculum Support Project Officer’.]

A topographic map uses contour lines to illustrate the height of a spot on the map.

[Screen shows an illustration of a topographic map. The lines on the map are labelled, ‘Contour line’. The map is titled, ‘Topographical map’.]

When you are familiar with contour line patterns, you can visualise what landform features are presented.

[The image zooms out to reveal an illustrated mountain range underneath the topographic map. The features of the mountain range match the contour lines of the original topographic map.]

For example, consistent circles spread evenly apart, rising gradually, will illustrate a hill.

[On both the topographic map and the mountain range illustration, the peak of the mountain is circled. These circles are labelled, ‘Hill’.]

A cross-section is a visual representation of a vertical slice of the landscape.

[Screen shows presenter standing in front of a decorative background.]

There are several steps involved in drawing cross-sections.

[Screen shows a topographic map of Newrybar and a folded piece of scrap paper. The presenter writes the letters ‘A’ and ‘B’ at two different places on the map.]

One, find Point A and B on your map.

[Presenter lines up the folded piece of paper so that the top edge is touching both letters. They draw a small line underneath each letter on the folded paper. The lines are labelled, ‘A’ and ‘B’. Next to the lines, the presenter draws a few small markings along the top of the folded paper. These markings show the positions of the different contour lines on the map.]

Number 2, place the edge of a sheet of paper along the transect and note A and B with the height above sea level that is illustrated on the contour line.

[Presenter makes additional markings on the folded piece of paper to show all of the contour lines between points A and B. Each marking is labelled with the height above sea level. The presenter also labels some notable landmarks, such as ‘creek’.]

Working from the left to right, carefully mark where each contour meets the paper and write the height above sea level.

[Presenter removes the map. They place the folded paper on top of a piece of grid paper, lining it up horizontally with the grid. The presenter begins drawing a graph on the grid paper. To create a horizontal axis, they draw a dot above where point A and point B are on the folded piece of paper. They remove the folded paper and rule a line on the grid paper between the 2 dots. They label the dots as ‘A’ and ‘B’.]

Draw a graph to plot the contours. The horizontal axis must be the same length as A to B.

[The presenter adds a vertical axis to the grid paper. Starting from point A, they draw a vertical line that is 5 centimetres tall. They draw an arrowhead at the top of the axis. Going upwards along this axis, the presenter writes the numbers 10, 20, 30, 40, 50, 60, 70 and 80. The axis is labelled, ‘Meters’.]

Choose a suitable scale for the vertical axis.

[Presenter brings back the folded piece of paper and lines it up with the horizontal axis. They plot each of the height markings on the graph by drawing a series of dots.]

Use the contour heights on your scrap piece of paper to plot the heights of each contour line on your graph.

[Presenter connects each of the dots by drawing a series of lines.]

Then you join these lines.

[Screen shows an animated cross-section of Launceston. The cross-section is titled, ‘Cross-section Launceston’. On the vertical axis, the graph starts at 0 metres and rises in regular intervals to 2000 metres. The axis is labelled, ‘Meters above sea level’. As the presenter discusses the key features, labels appear, marking them on the animated cross-section.]

Here we have a complete cross-section. Note the key features – title, labelled axes, and line graph.

[Screen shows presenter standing in front of a decorative background.]

A transect is a special cross-section on which other information about the area has been written. For example, landforms, vegetation or land use.

[Screen shows the cross-section of Launceston again. It zooms out to reveal additional information underneath the original graph. This information is presented in individual boxes that align with different features on the graph. Text on the screen reads:

  • Landforms – River flood plain, flat valley floor, undulating plains, gradually rising slope, steep incline, dolerite scarp
  • Vegetation – Cleared land, forest, wet and dry sclerophyll, alpine
  • Soils – Rich alluvial, very fertile, shallow, rocky, mainly rock (dolerite)
  • Transport – Well-developed infrastructure, minor sealed roads, farm roads and tracks, one main access road, poor condition
  • Settlement – Built-up area of Launceston, farmhouses, more dispersed with distance from Launceston, no settlement, Nation Park, alpine village
  • Landuse – Urban area, farming intensive, extensive farming, sheep and cattle grazing, forestry, national park ski village.]

Here is an example of a transect. Note the additional information about the cross-section.

[Screen shows presenter standing in front of a decorative background.]

Once you learn to use cross-sections and transects, you will understand more about topographic mapping. All the best with yours.

[Text on screen reads, ‘Acknowledgements. NSW Geography K-10 syllabus © NSW Education Standards Authority (NESA) for and on behalf of the Crown in right of the State of New South Wales 2015. See the NESA website for additional copyright information. NSW Department of Education Curriculum Secondary Learners. Southern Cross School of Distance Education.’

The screen shows an Indigenous artwork. The artwork features a landscape with native Australian animals. It is titled ‘Our Country’ by Garry Purchase. The text at the top of the screen reads, ‘Filming of these videos has taken place on Bundjalung land’. Video concludes by displaying the NSW Government logo.]

[End of transcript]

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