Mobile laser scanning for pruned stem detection

JAMIE DODD, GIS TECHNICIAN, HQPLANTATIONS IN AUSTRALIA also spoke remotely at ForestTECH. He highlighted Pruned Stem Detection in Araucaria Plantations using Mobile Laser Scanning.

About 40 000 ha of the land the company manages around Queenstown is allocated to Araucaria cunninghamii (Hoop Pine).

This low-resin wood, the only native conifer planted for timber production in Australia, allows for high-end applications in veneer and the like. With high-value pruned butts being worth up to four times the value of lower grade saw logs, pruning is critical to maximise the value of this species, he said.

“Pruning is expensive, so to make it cost-effective we want to only prune the trees with the best potential outcome, best form and the like,” explained Mr Dodd.

New scanning techniques thus come in valuable for decisions on which trees are worth pruning, particularly with no reliable external indicators to identify unpruned butt logs. The crew targets between half and two thirds of a stand, pruning to 4.8m at around a decade old.

The solution? Use mobile laser scanning in the form of the Emesent Hovermap ST-X. With 88% accuracy, the new Hovermap system provides high density data and good resource analysis, also avoiding double handling costs compared to a CT scanner, he added.

“Useful for foresters short- and long-term, extracting other metrics also allows for multiple outputs and an overall highprecision inventory of stems.”

The Hovermap allows for clear distinction between pruned and unpruned stems without manual annotation. Mr Dodd emphasised that the process is in its infancy and more work is needed on data collection, cost comparison with alternative methods, and noise around stemmed areas in the form of inherent variability of the subcanopy environment eg, thick undergrowth, small branches and close neighbouring branches.

He concluded that, “Any improvement in ability to identify pruned stems is useful given the significant price differential.”