Routes are PolylineM features that store measure values on their vertices to model the distance along a line. The measure values are stored on the vertices because, in many cases, the geometry of a feature is not as accurate as the measured lengths maintained for the feature. This can be the case for roads, pipes, railways, and other linear features. The routes maintain measures to support locating linear referenced events.
In the linear referencing system (LRS), the LRS editor associates centerline features and provides measure inputs using tools to create or modify routes. The tools to create or modify route features, also calculate and store the measure values on the route’s vertices. The centerlines are managed in a separate Polyline feature class and are associated with routes by the tools in the centerline sequence table.
The centerline sequence table allows the same centerlines to be associated with different routes in the same LRS Network (as is the case with concurrent routes) or with routes in different LRS Networks. This ability allows the same polyline geometry (centerline) to be used to create different measure systems (route features). Examples of measure systems include: continuous, engineering stationing, state mile point, and county mile point, all of which can be built on the same centerlines.
It is important to note that only LRS editors need to work with centerline features to build and edit routes. To locate linear referenced events on routes or to do measure or spatial analysis on routes does not require centerlines. In addition, the LRS editor need not work with the centerline sequence table explicitly. The tools take care of implicitly populating this table.
Centerline feature class
The centerline feature class is the geometry source from which routes are created. It must have an ObjectID field, a CenterlineID field, and From and To date fields. The CenterlineID is a system-generated GUID that associates centerlines to routes. The centerline feature class can be given a name that is appropriate to your business, but you may have only one centerline feature class per LRS.
Centerline sequence table
The centerline sequence table is a cross-reference table for the many-to-many relationships between centerlines and routes. The table must include the CenterlineID field, the RouteID field, the LRSNetworkID field, and FromDate and ToDate fields.