In the case of a line (single segment, polyline or curve) the common notion of the centre is simply the point on the line that is equidistant from the two endpoints. This provides both the (intrinsic) centre of gravity and the mean centre, although when a polyline is viewed as embedded in a plane its “centre” should be considered to lie in the plane and not on the line.

For collections of lines there is no generally applied formula and a common central point might be selected from the centres or centroids of the individual elements, or from the MBR, or utilising a central feature if one exists. Combinations of points, lines and polygons are treated in a similar manner. Because lines and line segments have a well-defined orientation, labelling tools that utilise line or segment centroids may also use the orientation of that element to align associated labels.