The central axis line of a wellbore or a pipeline with a position vector at each point of trajectory given as:

{\bf r} = {\bf r}(l)= \{ x(l), \, y(l), \, z(l) \}

where

	position vector of trajectory point with being a ture vertical direction
	path length from pipeline intake point
	well or pipeline intake point coordinates (usually )

In practice the trajectory is usually set by Deviation Data.

See also