Essential Roads and Highways vocabulary

Activity

Often used in the context of edit activities, which are discrete capabilities supported by Esri Roads and Highways to edit LRS Networks. Roads and Highways supports the following edit activities: create route, extend route, realign route, cartographic realignment of route, reassign route, and retire route.

ALRS

Acronym for the Advanced Linear Referencing System, a linear referencing system implemented by Roads and Highways on the ArcGIS platform that supports multiple linear referencing methods and event measure behaviors.

Asset

In the context of linear referencing, often refers to a type of linear referenced event that represents a physical object, such as a sign, guardrail, or bridge.

Calibration point

A point feature that defines the measure for a specific location on an LRS route. Roads and Highways uses calibration points to define the measures on the routes. The measures between two calibration points on a route are derived by linear interpolation.

Centerline

A polyline feature that defines part (or all) of the geometry of an LRS route. Routes in Roads and Highways can share centerlines in the same network (as is the case for concurrent, overlapping, or common routes) or routes in separate networks.

Event

In the context of linear referencing, refers to data that is located by its association to an LRS route and measure location. There are two types of events: point events that have a single measure and linear events that have a from and to measure along a route. Events are typically modeled in a database with a column for the route ID the record references, a measure column for the location on the route (two measure columns if it's a linear event), and a value (like speed limit). Additional temporal information on the time frames the event is valid can also be modeled.

An example of a point event is a crash location referenced to route Interstate 10 that occurred 10.53 miles down the highway. An example of a linear event is the record of a speed limit of 65 MPH on Interstate 10 from 0 miles to 20.5 miles.

Event behavior

In the context of linear referencing and Roads and Highways, event behavior refers to the configuration that defines how event measures and route associations respond to changes or edits in the LRS Network.

Roads and Highways, based on network edits, supports the following event behaviors:

• Stay Put: Keeps events geographically fixed in a location, which may result in event measures changing on modified portions of routes
• Snap: Reassigns (or snaps) events to dominant routes on modified portions of routes
• Move: Keeps event measures fixed, which may result in events geographically moving on modified portions of routes
• Retire: Retires events on portions of routes that change

Interpolative LRM

A linear referencing method that determines a location by interpolating between two known measures.

Linear network maintainer

GIS analyst responsible for editing the ALRS.

Linear event

An event that represents a segment of a route from a starting measure (or from measure) to an ending measure (or to measure).

LRM

Acronym for linear referencing method, a method for defining measurements along linear features for the purpose of linear referencing. Examples of LRMs are State Mile Point, County Mile Point, or Project Stationing.

LRS

Acronym for linear referencing system, the method of storing geographic locations by using relative positions along a measured linear feature.

LRS Network

A collection of routes, measured to a specific LRM in Roads and Highways.

Measure

A location along a route based on a distance from a known point of origin.

Point event

An event that represents a single point location on a route at a specific measure.

Project Stationing

A system of stationing in which the starting reference station is established at the base of a project location, and all distances along the route centerline are measured from that point location.

Redline

A feature in Roads and Highways that can be added to the redline feature class and can be used to communicate desired modifications to the LRS Network. The Roads And Highways Editing toolbar accepts redlines as input into the various network editing activities.

Referent

A fixed location along a route that has a discrete measure value from which other locations are determined.

Referent offset

A fixed distance from a referent; can be positive or negative.

Referent offset event

An event whose location is modeled as being a specific distance along a route relative to another event on the route.

Route

A linear LRS feature.

Station

Reference points that are placed along the horizontal measurement of a route, centerline, or baseline at a regular interval. Station numbers increase from West to East or South to North based on the cardinal direction of the overall highway

Stationing

The fundamental system of measurement used for road layout and construction. For highway projects, a starting reference station is first established and then all distances along the route centerline are measured from that point location. Generally, the distance between two adjoining stations along a route is 100 feet. The first station located at the beginning of the baseline is 0+00 and the next station located 100 feet away from it is 1+00. Therefore, a station number of 10+34.05 depicts 1034.05 feet (10*100 + 34.05) away from the starting station.