An underground mark is an artifact that is buried underground, beneath a station. Think of it as an emergency backup system. If the surface mark is ever disturbed or destroyed, the undergound mark may be used to re-establish the surface mark. It is never appropriate for anyone other than a professional surveyor to dig in an attempt to find an underground mark. If a datasheet talks of a surface mark and an underground mark, always leave the underground mark alone.

underground mark (last edited 2009-03-21 21:03:19 by localhost)