In September 2018, Typhoon Mangkhut ravaged the area around the hillside near HKUST’s waterfront. Specifically, a tree located in the area was nearly cracked in half. Severely damaged, Prof. WANG Yu-Hsing, Associate Head and Professor of the Department of Civil and Environmental Engineering thought it might not make it. However, the tree survived miraculously.
What fascinates the Professor the most is the tree’s resilience and tenacity in withstanding adverse weather conditions that have become more rampant due to climate change.
Thus, to monitor the tree’s stability, Prof. Wang installed a smart sensor at its lower trunk to monitor its tilting angle.
The sensor mounted on the tree was developed by the Professor and his research team who originally conducted a student-oriented project of using sensing technology on slopes seven years ago.
A Civil Engineering postgraduate and also a member of the research team stated, “As engineers, we want to find an absolute method to ascertain the health status of a tree. By studying a tree’s physics, we can accurately assess whether a trees tilting is non-reversible and if immediate action is required.
In 2017, the team was approached by the Hong Kong government to look into the potential adaptation of using the sensing technology on trees. Conventional sensors in the market failed to fulfil the two basic elements required to make tree sensors work: data transmission without interference in extreme weather conditions, and long battery life.
After successfully obtaining external funding for one and a half year beginning February 2018, for developing smart sensing technology to monitor tree stability, the team worked tirelessly for a year to eventually achieve a breakthrough in their smart sensor that uses the Low-power, Long-range Wide Area Network (LoRaWAN) for transmitting data in real-time while consuming low energy.
The data would then be sent to the data centre for big data analytics and timely interventions. Three generations of sensors have been developed throughout the funding period that quadrupled the data transmission range.
Effective tree management has always been a priority to the Hong Kong authorities as old and valuable trees in the city, being inextricably connected to nature, are prone to damages brought by typhoons, thus pose a high risk to people’s safety.
At the end of August 2018, the Hong Kong Observatory forecasted that Typhoon Mangkhut, the strongest typhoon in Hong Kong history, would sweep the city directly, prompting the team to optimize program design of the sensor and install 32 generation-three sensors on trees in Tai Tong and some urban trees within a week.
Although typhoon Mangkhut left the city with 46,000 fallen trees, it provided the team much valuable first-hand science-based data to analyse how and why certain trees fell and some others survived.
“What we ultimately aim to achieve is let AI provide a more solid diagnosis for tree health,” the Professor stated. “Even a tree is seemingly unhealthy, our sensor can continue monitoring it to allow it to recover instead of killing it at once.”
The sensors can also ease the heavy workload of the city’s hundreds of arborists. The team will start educating arborists on how to operate the sensors, and in turn, with their feedback, help to fine-tune the device.
After the external funding, Prof. Wang participated in the University’s two-year Sustainable Smart Campus project commencing in July 2019. With this, the team can continue developing the fourth generation of the sensor that can harvest energy from solar panels and conduct data analytics by AI.
