# Essential linear referencing vocabulary

This document introduces some vocabulary that is essential to understanding the linear referencing help.

TermDescription

Route

A route is any line feature, such as a street, highway, river, or pipe, that contains a unique identifier and a system of measurement. Routes are stored in a route feature class.

Route feature class

A route feature class is a collection of routes with a common system of measurement stored in a single feature class (for example, a set of all highways in a county). A route feature class differs from a standard line feature class in that, along with x- and y-coordinates, it also stores an m-coordinate (x,y,m).

Measure

A value stored along a linear feature representing a location relative to the beginning of the feature, or some point along it, rather than as an x,y coordinate. Measures are stored as m-values on route vertices. Measures can be any unit of measurement, such as miles, meters, and time.

M-value

A measure that is added to a line feature. M-values are stored in the m-coordinate of each vertex on a route feature. M-values are used to measure the distance along a line feature.

Events

An event is a linear, continuous, or point feature that occurs along a route feature. Anything that occurs on or describes a route feature can be an event. In the transportation field, examples of events might include pavement quality, accident sites, and speed limits. Events are stored in event tables.

Event tables

Event tables contain information about assets, conditions, and events that can be located along route features. Each row in the table references an event, and its location is expressed as measurements along a route feature. There are two types of route event tables: point event tables and line event tables.

Dynamic segmentation

Dynamic segmentation is the process of computing the map locations of events stored and managed in an event table along route features and displaying them on a map. The term dynamic segmentation is derived from the concept that line features need not be split (in other words, segmented) each time an attribute value changesâ€”you can dynamically locate the segment.

Using dynamic segmentation, multiple sets of attributes can be associated with any portion of an existing linear feature independently of where it begins or ends. These attributes can be displayed, queried, edited, and analyzed without affecting the underlying linear feature's geometry.