In addition, there are several private sector firms that maintain and sell road centerline files, including TeleAtlas and NAVTEQ. The grid is further divided by lines that run parallel to and between the principal meridian lines, called range lines. Road centerline data are often collected/disseminated by local governments or state GIS clearinghouses. Where a baseline meets a principal meridian is called a point of origin. In addition, road centerline data provide the foundation for car navigation systems. Examples include emergency dispatch, vehicle routing, address matching, road maintenance, and transportation modeling. The extensive attribute data stored with road centerlines facilitate their use in GIS in a wide variety of applications. It is possible to divide a section even further down to 2 1 2-acre tracts. Road centerlines can be used to encode road characteristics, including road name, road width, pavement type/conditions, number of travel lanes, travel directions, bridge weight limits, address ranges, speed limit, etc. Land descriptions are then generally made by referring to a particular quarter of a quarter of a specific section located within a township either north or south of the baseline, and either east or west of the principal meridian. Road centerlines can be developed through a variety of techniques, including GPS data collection and digitization of roads on aerial photographs. Road centerlines are vector line data that represent the geographic center of road rights-of-way on transportation networks.
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