The whole process of utilizing a surface area geophysical process or methods to interpret the existence of the subsurface utility and to mark its approximate horizontal place (its designation) on the ground surface. Virtually all underground utilities are privately owned and will not be marked by calling 811. Blood Hound https://f004.backblazeb2.com/file/DigitalAsset/Bess-Utility-Solutions-Hayward/Underground-Utility-Locating-Services-Near-Me.html