2　Terms

2.0.1　Pipelines

Generic name of the piping for different media，electric power cables，control/telecom cables or optical cables.

2.0.2　Above ground pipelines

Piping and electric power cables，control/telecom cables laid above/on the ground are normally supported by pipe rack，pipe sleeper，architecture/structure，and pole or steel tower.

2.0.3　Underground pipelines

The piping electric power cables，control/telecom cables may be laid underground，direct burial and laid in pipe trench，protection pipe or protection conduit.

2.0.4　Pipelines coordination

By overally arranging the spatial positions of all the systematic above ground and underground pipelines at the plant site，and comprehensively coordinating the relation between pipelines and relation between pipelines and other engineering facilities，the pipelines laid above ground and underground shall be arranged appropriately per specifications.

2.0.5　Piping belt

The strip area which is used to centrally arrange the above ground and underground pipelines.

2.0.6　Depth between pipe bottom and ground

Distance from the surface of ground to the internal bottom wall of the pipe.

2.0.7　Earth coverage thickness of pipeline

The vertical distance from the surface of ground to the top of the external wall of pipe.

2.0.8　Net horizontal distance

The horizontal distance between the external wall of piping（including protection layer），external wall of pipe trench or external edge of the cable/optical cable，or the horizontal distance between the external wall of piping（including protection layer），external wall of pipe trench or external edge of the cable/optical cable and architecture/structure，equipment.

2.0.9　Net Vertical clearance

When the piping，cable，optical cable or pipe trench are laid in neighboring arrangement，the net verticle clearance is the distance between the lowest point of the external wall of upper piping（including protection layer），the lowest point of the external edge of cable/optical cable or the bottom of pipe trench foundation and the highest point of the external wall of lower piping（including protection layer），the highest point of the external edge of cable/optical cable，the external top surface of pipe trench，or its height from the lowest point of the overhead pipeline（including protection layer）and its truss to the road or the top of railroad.

2.0.10　General survey of underground pipeline

The whole process of applications of economic，safe and effective techniques and methods to systematically and overally find out the present conditions of underground pipelines and pipeline associated facilities，obtain the accurate underground pipeline information，compile pipeline diagrams，and establish，update or complete the pipeline database and pipelines coordination information management system to implement the computerized dynamic management for pipeline information.

2.0.11　Underground pipeline exploration（detecting and survey）

The process to determine theattribute and spatial positions of the underground pipeline and pipeline associated facilities with techniques and measures including geological detecting and survey（abbreviated as exploration），find out the attribute data，spatial data，topological relation and logic relation of the underground pipelines and pipeline associated facilities，and to acquire accurate information of underground pipeline conditions.

2.0.12　Attribute data of pipeline

The data to describe the intrinsic information of the attributes and features of pipeline and pipeline associated facilities.

2.0.13　Spatial data of pipeline

The data to describe the spatial position，shape，distributionfeature，spatial relation，topological relation and logic relation of pipelines and pipeline associated facilities.

2.0.14　Information of pipeline

The general name for pipeline attribute data and pipeline spatial data.

2.0.15　Digital topographic map

The topographic map generated by computer and saved in computer data format per certain rules and methods for the topography information.

2.0.16　Feature points of underground pipeline

The starting/ending points，turning point，branch point，crossing point，gradient changing point，depth changing point，diameter changing point，material changing point，ground outlet/inlet，pole ascending/descending point，room outlet/inlet，wells（including rainwater well，sewage well，inspection well，maintenance well，valve well and instrument well）and the pipeline associated facilities are generally called as pipeline feature points.The underground pipeline feature points are divided into distinct pipeline points and concealed pipeline points per their exposure on the ground surface.

2.0.17　Exploration point of underground pipeline

For the underground pipeline in the as-built survey or in the underground pipeline exploration process，in order to accurately describe the position and routing characteristic of underground pipeline and find out the attribute data，spatial data，topological relation and logic relation of underground pipeline，the exploration points established in the underground pipeline and pipeline associated facilities are generally called the exploration points of underground pipeline.The underground pipeline feature points shall be deemed as the exploration points of underground pipeline.

2.0.18　Setover offset

The horizontal distance betweenthe exploration point of underground pipeline and the surface projection of the centerline of the underground pipeline.

2.0.19　Present investigation

The process to compile the pipeline position in the topographic map into present investigation diagram to provide reference of field exploration operation and attribute data basis of the relevant underground pipeline is based on the sorting，classification and analysis of the data gathered，and according to the coordinates and sizes specified in pipeline design diagrams，as-built diagrams or exploration diagrams in the site survey.

2.0.20　Pipelines coordination information management system

The computer management system to realize the input，edit，storage，analysis，query，statistics，diagram compilation，maintenance，updating and output of the pipeline attribute data and spatial data with the support of computer hardware，software，database and network，the application of the Geographic Information System（GIS）technology and the present topographic map as background.

2.0.21　Seamless jointing of map pieces

The process to conduct precise jointing of two pieces of maps which are originally connected and integrate those two pieces into continuous and consistent special data in logic and geometrical relations.

2.0.22　Maximum value method

The positioning by the position of the maximum value ofΔHx which is the difference of the horizontal component measured by the double vertical coils of the pipeline detecting instrument.when the pipeline detecting instrument cannot observe theΔHx，positioning should be done by the position of the maximum value of Hx as the horizontal component measured by single vertical coil.

2.0.23　Minimum value method

The positioning by the position of the minimum value of Hz as the vertical component measured by the horizontal coil.