I see these everyday.Metal studs in public pathways,I don't know why they're there,what is their purpose?

Question

Ref Pictures

http://fon.gs/stud1/

http://fon.gs/stud2/

http://fon.gs/stud3/

http://www.fon.gs/StudHere

Answer 1

I think they are survey reference points.

Answer 2

so that is waht they are

Answer 3

Brian A has got it right, they are surveyors spot marks.

Answer 4

They are PT nails used by surveyors to mark points.  They are not geodetic points, those have very official markers that actually say USGS on them.

Answer 5

is it aliens

Answer 6

Utilities (water, gas, electricity) use those to mark spots off where underground pipes/wires run.  Or, they could be marking any number of other things, like where they want to put underground pipes/wires.  I can't be exactly sure, but I just know it's them.

Answer 7

Actually called survey benchmarks.  They can be tied into the National Geodetic Survey system.

Answer 8

presume there something to do with spy satellites .

or maybe the local councils markers for theodolites