Any ideas?
Survey marker, used by surveyors to calibrate equipment. So I’ve been told, anyway.
A marker point for geodetic marking. Also known as triangulation station or trigonometrical point, it’s fixed to the ground with its known coordinates.
Cool! Interesting, I thought True North meant that they somehow pointed north given another reference. Thanks for the info.
Shotgun shells buried in the concrete. Don’t stomp on them too hard!
It controls where true north is, and if you remove it that will really mess with geographers and surveyors
Please don’t, people! I don’t want to have to re-learn geography with different orientations…
What city is this in? Because I’ve never noticed one in nyc
once you start to notice them, you’ll never stop seeing them everywhere.
this one is a magnetic nail, so it can be found more easily with a metal detector, which is pretty handy when there’s a foot or two of snow on the ground.
you’ll also see crosses, squares, and triangles carved out in stone, as well as the super common drill holes in concrete, which are typically only for temporary points.
I’ve found 100+ year old control points drilled into old stone walls, and they can still check within like ¼" of the new maps.
![[Solved] Anyone know what this is? They are embedded in the sidewalks around the city(programming.dev)](https://programming.dev/pictrs/image/17e2a431-e194-46bc-8e69-34c6419ac8da.jpeg){kind=link}