1. Overview
Underground pipelines refer to the underground pipes and cables buried beneath the ground, including water supply, drainage, gas, heating, industrial pipelines, as well as electrical and telecommunication cables. Underground pipelines are a vital component of urban infrastructure, and their spatial locations and attribute information are crucial basic data for urban planning and construction management.
Subsurface pipeline surveying involves measurements for the planning, design, construction, operation, and maintenance of various underground pipelines and their ancillary facilities. It can be categorized into new underground pipeline engineering surveying and existing underground pipeline detection surveying.
Existing underground pipeline surveying and measurement is the work of determining the spatial location and attributes of underground pipelines. Its purpose is to identify the existing underground pipelines' plan position, burial depth (or elevation), direction, specifications, nature, material, ownership, and other attributes. The nature of the work is to补救 the lack of completion surveying in underground pipeline projects.

　2. Design for Underground Pipeline Detection
　　2.1 Basic Technical Requirements
Prior to underground pipeline detection, it is necessary to collect, organize, and analyze existing underground pipeline and surveying data within the survey area. This data typically includes existing various underground pipeline maps, design, construction, and completion drawings along with technical documents, relevant topographic maps at corresponding scales, and the survey results of control points in the survey area and its vicinity.
The underground pipeline survey in cities should use the urban coordinate system and elevation datum; for pipeline detection in industrial areas or residential communities, and construction site pipeline detection, the building coordinate system of the survey area may be used if necessary.
Prior to the start of the survey, method tests should be conducted in the survey area or on nearby known pipelines to confirm the effectiveness, accuracy, and operating parameters of the methods and equipment. The scale and division indicators of the underground pipeline map should be consistent with the basic scale topographic map of the city.