A new, up-to-date thermal map of Brno has just been released, the result of a collaborative project between the City of Brno and the Czech Globe agency (part of the Czech Academy of Sciences). Aerial photography for the project took place during the summer.
“The city has been cooperating with scientific organizations on surface imaging since 2015, when we received the first data,” said Petr Bořecký, Brno city councillor for public participation. “Another temperature map was created in 2019. This year, detailed aerial photography was carried out using the most modern technologies on one day, 31 July. Thanks to this, we have up-to-date data on the temperature of the surface, its emissivity, i.e. the ability of the surface to radiate heat, as well as the brightness temperature. These images will assist us in city management and ecological planning. As can be seen from the pictures, there is no doubt that green roofs and streets have a positive effect on the microclimate.”
The temperature data is available to the public via an application operated by the GIS Department of the City of Brno, in cooperation with the Global Change Research Institute at the Czech Academy of Sciences. “You will find three summer maps and one winter map in the app,” said Tomáš Aberl, city councillor for information technology. “At the same time, everyone can compare the thermal image with an orthophoto map. The summary article also explains the significant factors that influence the city’s climate, which I believe will be of interest to a lot of people.”
The City of Brno spent about CZK 200,000 on the filming.
Thermal scanning of Brno
The city’s cooperation with the Global Change Research Institute (also known as Czech Globe) in scanning Brno’s surface temperature began with the creation of an initial temperature map in 2015, based on a summer and winter picture. This was followed by a summer picture in 2019, and another this year. Although satellite images are available showing surface temperatures, such as the Copernicus program’s Sentinel, Landsat, and others, aerial scanning images have a much higher accuracy and resolution.
This year’s thermal scanning used cutting-edge technologies from the Imaging Systems Air Laboratory (FLIS). Installed aboard a special Cessna 208B Grand Caravan photogrammetry aircraft, this airborne laboratory is equipped with advanced sensors and scanners. These allow the accurate recording of temperature and spectral information from the surface of the city, and create detailed temperature maps which can help analyse heat loss of buildings or assess the state of urban greenery, among other things.
Capturing the data
During the flight on 31 July 2024, the FLIS laboratory created images of the territory of Brno using hyperspectral and thermal sensors. Hyperspectral CASI-1500, SASI-600 and TASI-600 sensors produced by Itres recorded the surface along individual lines (so-called pushbroom scanners), which enabled the capture of accurate images with detailed spectral information. These data were then supplemented by the LMS Q780 airline laser scanner, which increased the spatial accuracy of measurements. The devices recorded data based on the aircraft’s position, which was controlled by precision navigation systems, and the data was synchronized with the GPS unit to enable further processing and georeferencing.
The scan took four hours, during which the plane was flying in a spiral above Brno, proceeding from the edges of the city towards the center, thus creating the flight lines. This technique minimizes temperature differences between adjacent flight lines, and creates an almost seamless mosaic of the city. Atmospheric conditions at the time of scanning were very favourable, with visibility over 40 km and almost no cloud cover, ensuring clear and consistent images.
Processing the data
After scanning, a series of corrections took place to ensure the accuracy and reliability of the data. Radiometric corrections adjusted the data to reflect actual surface temperatures, and georeferencing was provided by GPS units, together with a digital model of the surface of Brno. As a result, several types of outputs were produced that can be used for analyses:
- Land surface temperature, which determines how the surface of the city heats up.
- Land surface emissivity, describing the surface’s ability to radiate heat.
- Brightness temperature, which better expresses the perceived radiation.
How can the city use thermal data?
Thermal scanning is essential for city management and support for ecological planning. The data obtained from this project provides insight into the temperature profile of the city, and identifies places with higher temperatures which can become so-called “urban heat islands”. It is useful when planning the insulation of buildings or the expansion of green areas which naturally cool the environment. Thanks to accurate heat maps, it is also possible to design measures that help improve the city’s microclimate and thus the quality of life for residents.
Thermal scanning is thus not only an interesting use of innovative technology, but also has a practical use for the long-term management of the urban environment, boosting sustainable development in the city.
You can browse the thermal imaging map of Brno in English here.
