Underground utility mapping, also known as subsurface utility engineering (SUE), is a process that involves locating, identifying, and mapping underground utilities and other subsurface infrastructure. These utilities can include water and sewer lines, gas pipelines, electrical cables, telecommunications cables, and more.

The primary purpose of underground utility mapping is to provide accurate information about the location and depth of existing utilities before any excavation or construction takes place. It helps prevent accidents, damages, and costly delays that can occur if underground utilities are accidentally hit or damaged during construction activities.