What are those "survey" people doing with the yellow tripods?

you guys know what i'm talking about? it's either construction people or something doing some kind of survey and they have some machine with a yellow tripod. who are they and what are they actually doing?

[Jason Schneider]

The device you saw mounted atop a yellow tripod at a construction site is most probably a theodolite or a transit, both of which are used to determine boundary lines when sighted and aligned to a marker post. The tripods used are typically basic units designed for this purpose and not photographic tripods.

Thank you for bringing more information to this topic for me. Im truly grateful and really impressed.