How do you survey and map underground utilities?

Underground utility detection methods: ground penetrating radar (GPR) detects metallic and non-metallic utilities by radar reflection, electromagnetic locators detect energized or toneable metallic pipes, acoustic methods for pressure pipes, and traditional as-built records review. Field procedure: systematic grid scanning, mark detected utilities, survey positions with total station/RTK GPS. Data includes: horizontal position, depth, material, diameter, and condition. GIS integration creates utility maps. ASCE 38 defines quality levels from D (existing records) to A (verified by excavation). Critical for construction to prevent utility strikes.