Geography K–10 · Years 9–10

Measuring urban growth with a grid over annual satellite composites

NSW Stage 5 focus area Changing Places (2015 syllabus) and Changing places (2024 syllabus); ACARA v9 teaches urbanisation in Year 8 (Changing nations), outside this entry's Years 9 and 10, so only Year 9 skills codes are listed

PracticalLow risk

The idea

Urban growth can be measured, not just described, by counting grid cells of built-up land in satellite images of the same frame from two years.

What you need

Digital Earth Australia Maps (maps.dea.ga.gov.au): the DEA GeoMAD (Landsat, 1986 to 2025) annual true-colour composite for an outer-Sydney or regional growth area for two years at least 15 years apart, captured at the same zoom with the scale bar visible
A 1 cm grid printed on acetate; coloured pencils
ABS Regional population (estimated resident population by local government area) for the same area and the same two years

How to do it

Frame the same area at the same zoom for both years; confirm the scale bars match and record the ground size of one grid cell from the scale bar.
Lay the grid on each image. Classify each cell as built-up (more than half of the cell showing the grey of roofs and roads), vegetated, water or bare; tally.
Compute the built-up area in each year (cells × cell area) and the change in hectares and per cent.
Measure how far the built edge moved along one transect from the old edge to the new edge, using the scale bar.
Relate the change to the ABS population change for the same local government area over the period: hectares of new built-up land per 1000 extra people.

What you should see

Two tallies, a change in hectares and per cent, an edge advance in metres and a land-per-person figure. In a growth corridor the built-up count is expected to rise and the vegetated count to fall between the two years; the exact figures are the class's measurement. Each composite is an annual 'average' of the year's images for every 30 m × 30 m pixel (Geoscience Australia's description of DEA GeoMAD), so a cell smaller than about 30 m on the ground cannot be classified reliably. It worked if a fixed landmark sits in the same grid cell on both images and the cell size was read from the scale bar.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Cities grow only by building taller, not by spreading.
A satellite image is a single photograph taken on one day.

Safety card

Low riskLearners carry it out

Hazards

No hazard is listed.

Controls

No control is listed.

Note

No chemicals or heat are used. The activity is run under the school risk-assessment procedure; RiskAssess (riskassess.com.au) holds templates for school practicals and fieldwork. The NSW Department of Education Chemical Safety in Schools package is not triggered.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Geography K–10 Syllabus (2015), NESA; current and taught in 2026, replaced from 2027. The outcome codes are not printed on the NESA landing page for this syllabus, which only links the document, so the url given is the syllabus document itself (geography-k-10-syllabus-2015.docx); the code and its outcome text were read in that document on 23 September 2026.GE5-2 GE5-3 GE5-7
Geography 7–10 Syllabus (2024), NESA; implementation from 2027, not yet taught; code read on this page on 22 September 2026GE5-PRI-01 GE5-TAP-01
Australian Curriculum v9AC9HG9S02AC9HG9S03

Sources

The pages the author read to write this activity.

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