Under the PolyU-led Jockey Club Smart City Tree Management Project, Smart Sensing Technology (SST) and Geographic Information Systems (GIS) will be applied in monitoring the stability of trees. Dr Charles Wong at the Department of Land Surveying and Geo-Informatics talked about the significance of this project.

1. What is the importance of this project?

Trees in Hong Kong are subject to the impact imposed by internal and external factors, including biological and environmental limitations like weather and climate change. Wind force on the canopy and lower trunk of a tree generates a reaction momentum at the tree base. However, if the root system is not strong enough to sustain the force, the tree may tilt or even uproot and fall. It is therefore important to establish a tree stability monitoring system to facilitate green management in the city for longer tree lives, to further improve air quality and enhance the living environment.

2. How can the conditions of trees be monitored?

Tailor-made sensors will be installed on the lower trunk of selected trees to monitor their tilting angle in a 3-dimensional manner. Using SST and GIS, a system will be developed to collect and analyse the data collected from the sensors via the application of GIS-based platform and the use of Big Data technology. That system can monitor trees on a massive scale and on a daily basis, showing the trees’ geographical location, their stability and any change in tilt angles.

3. If the system displays a warning message, what actions will be taken?

Taking various environmental factors into consideration, a threshold will be determined by the project team to measure the root plate movement and stability. When a sensor shows that the tilting angle of a tree exceeds the threshold, the system will alert the project team to conduct a visit and verify the data and calibrate the system. When deemed necessary, the relevant tree management team will be informed to undertake actions in a timely manner.

The monitoring system will provide objective and quantifiable data for the reference of the tree management team to supplement visual tree monitoring now widely adopted by the industry.

4. What is PolyU’s role in this project?

With a funding of HK$32.28 million from the Hong Kong Jockey Club Charities Trust, this 3-year project is led by PolyU and was commenced in February 2018. Other collaborators in the project include the University of Hong Kong, the Hong Kong University of Science and Technology, and Friends of the Earth (Hong Kong).