PCC Lines are shown by major branch lines. This data is used as 1) a linear referencing system (LRS); 2) for locating features on the PCC system by milepost value. PCC lines were built using existing data sources including railroad line track charts, track right-of-way maps, and recently digitized linework based off aeiral photos. In LRS, the locations of both data and events are determined according to their distance along a railroad line from some known point (e.g., the beginning of the line or line segment, a mile marker, a junction with another rail line, or a railroad crossing).