tombstone surveying

Tombstone surveying is a technique used in geology, engineering, and construction to accurately mark and map underground features or boundaries. It involves installing a metal or concrete marker, called a "tombstone," at a specific location, which serves as a fixed reference point. Surveyors then measure from this point using precise instruments to determine positions, depths, or extents of subsurface structures or utilities. This method ensures consistent, reliable data for future reference, construction planning, or safety assessments, especially in complex or congested underground environments.