Working with Skopje’s Innovation Lab has led to some surprising technical solutions to development challenges but none more so than our latest project — using a paraglider and a thermal camera to assess the effects of urban heat islands in the capital city.
What are urban heat islands?
Urban heat islands are areas that have significantly higher temperatures than surrounding non-urban areas. These ‘islands’ arise because extensively paved and heavily built-up areas serve to amplify and trap heat. This is in addition to other heat and waste heat sources within cities, such as from vehicles, industry and air-conditioning. Unlike natural ecosystems in rural areas, cities lack sufficient trees and vegetation to absorb heat and provide shade.
The negative impacts of urban heat islands will be greatly exacerbated by climate change. The interaction of rising temperatures and more frequent and severe heatwaves with the effects of urban heat islands will increasingly deplete the quality of air and water, further threatening the health of urban populations.
For these reasons it is vital to identify existing urban heat islands (UHIs) in Skopje in order to inform the development of evidence-based policies for mitigating their effects.
Thinking outside the box to collect data
To identify and assess the effects of UHIs in Skopje, we first needed to work out the most effective way of collecting data on air and surface temperatures. Typically the temperatures of large urban areas are measured using satellites, aircraft and/or ground-based instruments. Considerable costs are involved, however, in leasing aircraft, purchasing satellite images or building a dense network of sensors. Moreover, while satellite images can capture the general UHIs within a city, they cannot show variations in air temperatures across neighbourhoods or on the streets.
Given these constraints and cost-considerations, our first solution was to use a drone combined with a thermal camera. This approach proved unfeasible, however, partly because the area of Skopje is too large and partly because it is forbidden to operate a drone in some areas of the city.
The solution we finally came up with emerged in the course of a discussion with one of our Masters students. It turned out that this student was a keen paraglider, and so naturally we started thinking of ways to mount a thermal camera on a paraglider to fly over the city.
The mount needed to be able to hold two cameras: one thermal and one standard RGB camera. So we first created a 3D model of the mount and printed it out on our 3D printer. For this, we used our Flir Vue Pro thermal camera, which detects the infrared portion of the magnetic spectrum presenting the current temperature of the recorded surface. This camera enables the calculation of the relative temperature between two points on the image, thus providing information about the heat of a single point relative to another. As an RGB camera, we used a GoPro 4 camera that was also taking pictures at the same time as the thermal camera.
The paraglider launched from Mount Vodno and flew down to the City Park over the centre of Skopje. This flight alone collected over two thousand thermal and standard RGB images. Each thermal image was then paired with an RGB image by using the time information of the snapshot. Both cameras were synchronized and set up to take one image per second. Some of the image pairs we created are shown in Figure 1.
Figure 2 shows the temperature profile of the city of Skopje based on GPS log from the flight:
The range of temperatures we obtained proved the presence of UHI effects in Skopje. This is shown in Figure 3, a map of the probes of thermal information collected from thermal photos.
What results did we get?
- The range between the maximum surface temperatures in the periphery of the city is approximately 7 degrees. The variance found on Mount Vodno is much higher, however, reaching about 12 degrees.
- The highest temperature is found in the central core of the city — Gradski Zid. Average temperatures this area are 1.5 to 2.0 degrees higher than in the Skopje municipality of Kisela Voda.
- The River Vardar has a positive impact, lowering surrounding temperatures.
- Higher temperatures are recorded in areas with more reflective roofs..
We also obtained detailed data from a micro-analysis of the central city area around the main square, including the streets of Maksim Gorki and Nikola Vapcarov. The following key findings are based on the thermal images presented in Figure 3:
- The reflective white tiles in the main square result in a lower temperature than surrounding asphalt areas (1).
- Darker rooftops are significantly hotter than lighter and more reflective rooftops (2).
- Parked vehicles accumulate heat and directly influence the temperature of Maksim Gorki Street (3).
- Nikola Vapcarov Street is significantly cooler than Maksim Gorki Street due to shade from trees and the absence of cars. (4).
This pilot project has proven the effectiveness of using our methodology to assess the intensity of urban heat islands in the city. However, in order to develop a thermal map of the whole urban area of Skopje, we would need a small plane.
Want to partner with us on this initiative? Get in touch!
This research project was conducted with resources from the 2016 Innovation Facility, generously funded by the Government of Denmark.
* This blog is based on the paper ‘Analysis of the urban heat islands effect in Skopje’, delivered at the 15th International Conference on Informatics and Information Technologies.
Dimitar Trajanov, PhD, Professor at the Faculty of Computer Science and Engineering of the University of SS Cyril and Methodius, Skopje, Macedonia. (Ruger Boskovik 16 Skopje — Macedonia.)
Kostadin Mishev, PhD student at the Faculty of Computer Science and Engineering of the University of SS Cyril and Methodius, Skopje, Macedonia. (Ruger Boskovik 16 Skopje — Macedonia.)