Hidden in thick scrub between Mona Vale Road and the footpath, only the substantial stone cairn of the Addison Trig remains. There is no evidence of the mast or vanes.
A Statement of Heritage Impact for the Mona Vale Road West Upgrade found that the old trigonometric station had no heritage significance. It was described as “consistent with early examples of trig stations”, but “Although used for many years in surveying of the area, as an arbitrary point for measurement the cairn is not considered as important to the area’s cultural history.” Although not impacted by the road-widening project, the stone cairn is gradually being obscured and buried by the surrounding bush.
Getting to the Addison Trig
The Addison cairn is reached by following the paved footpath from Addison Road (which is off Lane Cover Road) about 220m towards the Bahai’s Temple. Although the trig point is only a few metres away from the pach, you’ll need to push through the scrub to actually see the stone cairn.
- RPS Australia – A Statement of Heritage Impact for the Mona Vale Road West Upgrade [PDF]