The centerline is an imaginary line through the exact center of a design element, relative to a force or object interacting with it. The centerline may represent a horizontal or vertical center.
In the design process for a trenchless construction project, the centerline is a line that bisects a design path, a pipe or other physical feature or structure.
Trenchlesspedia Explains Centerline
The centerline may represent the ideal path for a pipe or bore to follow, which offers a minimal loss of pressure or interference with surface activities. The centerline, however, does not define the size of a pipe, structure or other physical feature; it represents only the location of the center of a feature.
In the "as-built" drawings of any portion of a trenchless construction/rehab phase of a project, the centerline reflects the center of the pathway the project was required to follow by on-site changes or circumstances or differences between geotechnical reports and actual conditions.