During summer 2016, Drone.UA together with ecological club “Green Wave” had performed thermal aerial mapping of districts of Kyiv city within the project “Management of urban green areas as an element of adaptation to climate change in cities” under EU financial support (Climate Forum East II, National Ecological Centre of Ukraine). Center for Aerospace research of Earth (CASRE) also contributed to the project. The research was aimed to improve sustainable management of urban vegetation for providing comfort conditions for citizens under “heat waves” which nowadays occur in every big Ukrainian city due to climate change.
To find out how temperatures allocate around specific facilities such as buildings, trees or flowerbeds, Drone.UA experts used thermal imager Flir Vue Pro and multi-rotor unmanned aerial vehicle (UAV) DJI Matrice 100 to carry out thermal imaging. The survey was performed from the height of 100 m, that allowed to obtain thermal maps with spatial resolution 1-2 cm.
The UAV was also equipped with a regular RGB camera, and thermal maps could therefore be compared with visual maps. Data processing and generating of georeferenced maps was performed with Pix4D software.
Figures below demonstrate visual and thermal maps of three residential blocks with various vegetation density. Density is calculated as estimated surface coverage by vegetation and is equal to 7%, 35% and 47%.
1. Visual and thermal map of the block on the northern side of Zhylyan-ska Street between Symona Petlyury Street and Lva Tolstogo Street. Estimated vegetation coverage is 7%.
2. Visual and thermal map of the block on the northern side of Zhylyanska Street between Tarasivska Street and Pankivska Street. Estimated vegetation coverage is 35%.
3. Visual and heating map of residential block and buildings of the military hospital on the corner of Lesya Ukrayinka Blvd and Novogospitalna Street. Estimated vegetation coverage is 47%.
The maps provide good illustration of several cooling capacities of plants:
- Surface temperature of trees and grass plots is significantly lower than temperature of other surfaces. While temperature of asphalt and roofs can reach 45°С and more, vegetation does not heat above 25–30°С. This is primarily caused by higher reflection of sun light (vegetation is lighter than asphalt), and, secondly, by evaporation of water from the leaf surface, which results into temperature drop.
- Tree surface is cooler than surface of grass plots. The reason is that the volume of canopies is larger than the volume of grass plots, and therefore trees have higher heating capacity per square meter of surface.
- Most trees create good shade sufficient for significant cooling of the shaded surface. Temperature of shaded surfaces can be close to temperature of the plant itself, i.e. 25–30°С.
- Vegetation can reduce surface temperature even beyond the shaded area. Around the shaded area there is a small zone where surface temperature is 3–5°С lower than in the remaining open area. This zone will be larger if surrounded by shaded areas from all or a few sides.
Besides the UAV-based thermal mapping, the project’s activities included gas exchange measurements of different trees to detect their stress tolerance and CO2 utilization capacity. Analysis of satellite thermal and visual images was held for determining cooling effect of urban vegetation at the city level. Ukrainian legal framework dealing with urban green zones and its readiness to face climate change has also been analyzed.
Drone.UA: experts in UAV technologies and thermal mapping
Alexandra Khalaim: coordinator of the project
Taras Kazantsev: principal investigator of the project
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