Survey control point.
Hmm.
What is the significance of that?
I’m thicker than usual today...
Land surveyors use them to ‘calibrate’ their equipment. Usually an orange or pink triangle with a stable point in the middle, like a nail. Not unusual in the center of the road.
Also, I don’t think ‘what’ it is is quite as important as why it’s there and what it may represent. I am a land surveyor and I missed it. Good eye!!
I will be thinking on that one.