Urban sprawl is a complex and often controversial issue. Depending on your perspective, it could offer the chance to live in a quieter, greener neighbourhood or signal a loss of farmland and a driver of climate change.
Regardless of perspective, Earth Observation (EO) offers a valuable way to monitor urban expansion, identify new developments, and assess the pace of growth. Mallon Colleague Anastasiia Khil has created the following maps, which provide a fresh perspective and understanding of urban sprawl.
How Earth Observation Can Address Urban Sprawl
Both radar and optical satellites can be used to detect built–up areas. Optical imagery captures scenes in true colour and multispectral bands, while radar data reveals surface roughness and structural changes. Each has its limitations, but when combined, they provide a more comprehensive picture of urban development. This enables more accurate monitoring, planning, and evidence–based decision–making.
For this study, we used data from the European Union’s Copernicus programme:
- Sentinel–1: Radar imagery, launched in 2014, with 10m resolution and revisits every 3–4 days
- Sentinel–2: Optical imagery, launched in 2015, with 10m resolution and revisits every 2–3 days (though cloud cover often limits usable data)
Using Machine Learning to Detect Development
This research examined urban growth in Dublin and its suburbs between 2019 and 2024. A Random Forest classifier was applied, using Sentinel–1 backscatter data (in VV polarisation) alongside Sentinel–2 spectral bands (Blue, Green, Red, NIR, SWIR).
To ensure accuracy:
- Training data came from ESA’s WorldCover 2021 product
- A balanced sample of 1,000 points was used
- The model achieved92% accuracy on the test set
Time–series analysis reduced false positives, although some bare soil and crops were occasionally misclassified as construction. Overall, these errors had only a minor effect. By comparing binary masks across years, newly built areas were detected and mapped.
Mapping Dublin’s Sprawl
Over the past five years, Dublin’s core city has changed relatively little. Built–up areas increased by just 4.5 km² (<1%), primarily in the northwest (Ballycoolen, Mitchelstown) and southwest (Brownsbarn, Fortunestown). The bulk of new development is occurring outside the established city.
- Within 5 km of Dublin: Growth amounted to 11.2 km² (1.7%), making this the most active development zone. Notable construction was seen in Hollystown, Finnstown, Deansrath, Greenogue Townland, and Kilruddy. Major projects included Dublin Airport’s expansion and the new Meta Data Centre in Clonee
- 5–10 km from Dublin: Expansion was slower, with 4.7 km² (0.6%) added. new development took place in Donabate, Rolestown, Maynooth, and Celbridge
Conclusions
Between 2019 and 2024, Dublin added more than 20 km² of new built–up areas, mainly in the suburban fringe. The city itself is largely established, but steady expansion continues around its periphery.
This research demonstrates how EO techniques can support urban monitoring and suitable planning by enabling authorities to:
- Track urban growth and density over time
- Measure the pace and location of expansion
- Assess environmental and land–use impacts
- Inform smarter, more sustainable urban development strategies
Further Information
For further information about the methods used to produce the maps above or to discuss your Earth Observation requirements, contact us below.
