Tree management: An example of human-machine collaboration

October 12, 2023 06:00
Photo: CLP

According to the World Economic Forum's 2023 Future of Jobs Report, many emerging jobs will require human-machine collaboration. CLP's recent innovative system on tree management (System) is an excellent example. Trees close to overhead cables often interfere with the cables, resulting in voltage instability. If a tree falls and pulls down the cable, it can even cause a power outage in a wide area, and the new forecasting system is the solution to tackle the problem.
It has three major benefits:

1. Precision

CLP set up a tree repair team of about 40 people to prune trees as early as 2001. But without a complete tree database, it was difficult to grasp the growth of trees within the vicinity of cables, which made the work not very efficient.

Today, using the geographic information system (GIS) at its core of the System and linking data from more than 170,000 trees within the overhead cable range, the efficiency is much enhanced.

The comprehensive tree database contains tree species, age, tree repair records, and growth equations based on the relationship between sunlight, temperature, and rain, helping the team to understand and predict the growth of trees in order to estimate their distance from nearby overhead cables. With the professional assistance of Professor Jim Chi-yung, Research Chair Professor of Geography and Environmental Sciences at the Education University of Hong Kong, the tree repair team monitors trees with scientific indicators to reduce risks.

The closer the tree is to the overhead cable, the higher the risk level, which is displayed in different colors on the map within the system. This allows the tree repair team to prioritise the pruning work.

2. Efficient

The tree repair team established more than 20 years ago mainly relied on experience to estimate the growth rate and direction of trees, and needed to undertake regular on-site inspections to visually identify trees that pose potential risks to cables, which is both labour intensive and time-consuming.

Today, the new system has a mobile application that can not only input and update tree data on the spot, but also connect to the Global Navigation Satellite System to let people know exactly where trees need prune and with related information, including tree species, height, canopy width and size, making it easier for management to arrange suitable manpower, such as the combination of team size with suitable ability, tool requirements, and more.

It also helps the team to formulate appropriate tree management measures and tree repair schedules to enhance work efficiency. In fact, the team has completed as many as 80,000 pruning jobs in the past year.

The media reports mentioned that a tree team member climbed up a tree and worked with another team member on ground who advised the tree repairer the exact location of the branches to be pruned through the walkie-talkie, and the whole process took only about an hour.

3. Save money and reduce emissions

CLP said that the new system not only improves the reliability of power supply, but also reduces operating and maintenance costs, and is expected to reduce operating costs by 1.5 million Hong Kong dollars each year. At the same time, the tree repair team can instantly import the tree records obtained on site, reduce paperwork, reduce paper consumption by 70%, and cut down carbon emissions.

Identifying trees with potential risks to cables through human-machine collaboration should be an inspiration to other organisations such as MTR with many overhead cables. Further, its scientific way of trees monitoring makes it easier to identify dangerous trees, and the government departments responsible for protecting trees in Hong Kong can also learn from them.

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Adjunct Professor, Department of Computer Science, Faculty of Engineering; Department of Geography, Faculty of Social Sciences; and Faculty of Architecture, The University of Hong Kong