What is a linear referencing system?

A linear referencing system consists of a set of line features, on which events, elements, and characteristics can be located based on a reference to the line itself rather than through absolute x,y coordinates. Events are things that happen on or to the line feature, such as crash locations and highway projects. Elements are objects that exist on or near the line feature, such as signs or guardrails. Characteristics describe the line features, like speed limits or number of lanes. In ArcGIS, the term event is used to represent events, elements, and characteristics when they are stored in tables that use a relative distance from the starting point of a line, called a route, to describe a location.

You can use a linear referencing system to represent a transportation network as well as items associated with route sections on the network such as crashes, signs, road conditions, and construction projects. The route line features serve as the base for the locations of the network features. Events such as crashes are rendered as points, while pavement conditions and speed limits can be represented as line features on the map.

In the example below, the aerial photograph is displayed with a line feature class, with streets and events rendered on it. The signs are represented as points, and pavement conditions are represented as lines. Construction projects are also rendered as a brown line along routes and overlap the pavement condition events. The locations of the construction projects could be related to the condition of the pavement to ensure projects are in place where the road conditions are poor rather than good.

Example of a linear referencing system with events

The linear referencing system tools in Production Mapping allow you to work with linearly referenced events on routes. This includes the ability to create, move, modify, and split events as appropriate for your data.

Both point and line events can be created using the event layers that are currently loaded in your map. After they are created, you can move point events along corresponding route features; line events can be extended or trimmed as needed, split at a specified location; shared line events can be adjusted based on the to- or from-point; and both types of events can be deleted.

The tools allow you to work with events visually instead of modifying table records. That is, instead of updating a value in a measure field, you can drag a point in the map to move it.

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