GEORGE TOWN: Satellite imagery alone cannot determine the risk of a large heritage tree falling, said Penang Island City Council (MBPP) mayor Datuk A. Rajendran.
He said while the technology could assess a tree's foliage health, it could not detect hidden internal or structural defects, particularly in mature Angsana Heritage Trees.
"At this stage, the council only has the artificial intelligence (AI) I assessment of the tree's foliage condition, which has been completed based on satellite imagery data.
"The AI prediction for tree fall risk is based on a combination of datasets, including satellite imagery, Mobile Light Detection and Ranging ( LiDAR) scanning of tree structure, environmental data and other relevant LiDAR-derived information," he said.
Rajendran said the satellite imagery assessment had an estimated accuracy of around 94% for foliage-related health assessment, but this should not be interpreted as a 94% accuracy in predicting whether a tree would fall.
He said MBPP expected the assessment to become more comprehensive once structural data from mobile LiDAR, environmental data and other LiDAR scanning results were integrated.
"This will allow the AI to consider both foliage condition and structural characteristics that cannot be assessed from satellite imagery alone," he said.
On the tree that fell along Jalan Macalister on Sunday (Aug 9), Rajendran said the absence of recorded high wind speeds did not rule out localised wind effects.
He said tall buildings on both sides of the road could have altered wind flow and created areas of increased turbulence or localised wind effects, placing additional stress on a tree with existing structural and root weaknesses.
The Angsana tree, estimated to be about 90 years old, about 28m tall with a trunk diameter of about 2m, fell onto a car carrying three people, injuring all of them.
CCTV footage of the scene showed just seconds before the tree crashed to the ground, a public bus had stopped nearby while several cars and motorcycles passed beneath it, including a passenger who had just disembarked from the bus, all while the tree was seen slowly slanting sideways.
MBPP 's initial assessment found about 30% of the tree's root area had deteriorated, while a cavity affecting about 40% of the base of the trunk was also detected.
Rajendran said as of July 31 this year, MBPP had felled 247 trees based on satellite imagery and invasive techniques used to assess tree health and stability.
He said the council was also using Ground Penetrating Radar to identify the spread of tree roots.
