Hong Kong’s PolyU to apply smart sensing technology in urban tree management

The Hong Kong Polytechnic University (PolyU) recently kicked off the Jockey Club Smart City Tree Management Project. The large-scale pilot project in Hong Kong seeks to apply smart sensing technology (SST) and Geographic Information Systems (GIS) for monitoring tree stability to enhance timely appropriate mitigation measures for sustaining longer tree lives.

“Committed to the pursuit for application-oriented research, PolyU researchers will apply smart sensing technology and Geographic Information Systems for monitoring tree stability. Our vision of establishing this system is to facilitate green management in the city for longer tree lives, so as to further improve our air quality for enhancing the living environment for the local community,” said Dr Miranda Lou, Executive Vice President of PolyU.

Members of the PolyU-led Project team include the University of Hong Kong (HKU), The Hong Kong University of Science and Technology (HKUST), and Friends of the Earth (Hong Kong). The project also receives support from relevant government departments.

In the Project, sensors will be tailor-made and installed on the lower trunk of selected urban trees to monitor their tilting angle in a 3-dimensional manner, as a way of assessing the stability of the root and thus the tree. This is because tree anchorage is critical to its structural stability. Weak anchorage will be reflected in a tree tilting, which in serious case poses the hazard of falling.

Ir Hon Chi-keung, JP, Permanent Secretary for Development (Works) of HKSAR Development Bureau, said, "This project is a good opportunity to showcase Hong Kong's positive attitude towards innovative technologies and technology applications. Through the close co-operation between the tree management departments and the project teams, an effective tree monitoring system will be established to enhance the tree management works in all aspects, enabling the continual development of Hong Kong into a safe and liveable city."

Data collected will be used for a quantifiable analysis of the trees’ root plate movement through the use of SST, i.e. the technology of monitoring environmental changes with the use of remote sensors and techniques, via the GIS-based platform.

Taking into consideration of various environmental factors, a threshold will be determined to design the monitoring system as a scientific measurement of the root plate movement and stability. When the tilting angle of a tree exceeds the threshold, the project team will be alerted to conduct a visit to verify the data for the purpose of calibrating the system. When considered necessary, it will inform the relevant tree management team to undertake actions in a timely manner.

As such, the information generated by the monitoring system will provide objective and quantifiable data for the consideration of the tree management team to supplement the visual tree monitoring method widely adopted by the industry at the moment in assessing the movement of a tree.

The Project started in February 2018 and SST sensors will in due course be installed on approximately 8,000 urban trees across the territory for monitoring over a 3-year period. It is expected that the Project will provide scientific data to supplement the existing tree preservation mechanism through early notification and response, aiming to contribute towards sustaining the invaluable urban trees in the city.

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