Mapping Urban Heat: Geospatial's Role in Cooling Cities Urban heat mapping

March 6, 2025

When we think of urban heating, we usually think of trees. We all know that trees contribute significantly to the cooling of urban areas. But dark roofs have a substantial impact on temperature across Australian cities, with recent studies revealing concerning trends. Urban heat mapping solutions, such as aerial thermal sensing, are becoming essential tools for identifying and addressing these heat-trapping surfaces in our cities.

The heat trap: how dark roofs affect our cities

Dark roofs can make urban areas up to 10°C hotter than surrounding rural or coastal suburbs. This temperature difference is particularly pronounced at night, when cities struggle to cool down. In some areas, residential buildings with dark roofs experience up to 100 more hours above 26°C per summer compared to those with reflective roofs.

The science behind this is straightforward: dark materials absorb more solar radiation. On a typical sunny day, a dark roof can absorb up to 95% of incoming solar radiation, while a reflective roof might absorb as little as 20% .source.

The cost of keeping cool

This urban heating doesn’t just affect our comfort—it hits our wallets too. Households with dark roofs can spend up to $700 extra annually on cooling costs. In some cities, power bills for homes with dark roofs are 38% higher than those with lighter roofs.³ Across Australia, the additional air conditioning costs due to heat-absorbent roofs contribute to over $1.3 billion in summer cooling expenses.¹

Mapping the heat: new technologies for urban planning

To address this issue, innovative approaches are being developed. One such method involves aerial thermal imaging, which can quickly detect and quantify dark roofs across entire suburbs. This technology captures heat signatures absorbed and retained by roofs, creating a thermal picture of urban settings.

How we map urban heat

Using aerial thermal imaging, Outline Global precisely measures heat absorption across urban surfaces, including dark roofs. Our advanced sensor system captures data across multiple spectrums—from visible light (RGB) to infrared wavelengths including short-wave, medium-wave, and long-wave infrared. This comprehensive approach creates detailed thermal maps that identify heat-retaining hotspots in urban areas.

Comparison of wavelength, frequency and energy for the electromagnetic spectrum (Credit: NASA’s Imagine the Universe)

Outline Global’s specialised Forward-Looking Infrared Camera operates in the Long Wave Infrared (LWIR) spectrum (7.5-12 μm), providing factory-calibrated temperature measurements accurate to ±2°C within a range of -20°C to 150°C. This accuracy accounts for varying surface emissivity values—from low-emissivity polished metals like copper and aluminium (below 0.1) to higher-emissivity materials like ceramic tiles. This detailed thermal data enables our customers to target effective urban cooling solutions.

The image below shows thermal data captured in Queenscliff, Victoria. We flew in the afternoon to take advantage of the westerly sunlight, which better highlights heat trapped in urban areas. This timing allows us to clearly see how different surfaces retain and emit heat, providing valuable data for urban heat management. Roofs with a higher emissive value had been mapped. The left-hand side is an 8-bit greyscale mosaic highlighting roofs that exceed an absolute temperature value that was determined by our client.

Roof Feature Extraction, from left to right, LWIR, RGB, and ARD (Analysis-ready-data – Vectors).

Cooling cities with data-driven solutions

Urban heating is a growing challenge—but it’s one we can address together. At Outline Global, we provide the tools and expertise to measure, understand, and mitigate urban heat. Using thermal imaging technology, we map heat-retaining surfaces like dark roofs and provide actionable data for reducing their impact.

Our solutions are designed to support councils, developers, and policymakers in creating more livable cities. Whether you’re planning new developments or retrofitting existing urban spaces, our expertise ensures you have the tools to make informed decisions.

References

Aerial Imagery Blog Uncategorized

Mapping Urban Heat: Geospatial’s Role in Cooling Cities