Surveying relies on physical reference objects placed in the ground. While temporary stakes are what the public may see most often in conjunction with construction work, the enduring reference marks (usually called monuments) are much less prominent. Monuments serve to mark points used for geodetic control networks as well as points used to reference property boundaries. Monuments can take a variety of forms.

http://www.sco.wisc.edu/land-surveying/monument-maintenance....

Geodetic survey monuments, usually consisting of a metal disk placed in top of a concrete post, have been placed throughout the county.

http://www.greenwoodsc.gov/countywebsite/modules/showdocumen...