LRS data model

The linear referencing system (LRS) is a collection of feature classes and tables that allow the storage and editing of calibrated routes.

The LRS supports the use of a single polyline feature class, known as a centerline, to store the geometry for multiple routes. Centerline geometry, along with route definitions, are stored in a network feature class.

A many-to-many relationship exists between the routes in the network and centerlines providing the geometry. This means that routes are typically composed of multiple centerline features, and centerline features can participate in multiple routes in multiple networks.

In addition to geometry, routes must also have measures. The LRS uses route measures so that event layers appear in their correct locations on a map. Measures are added to routes through a process known as calibration. To explicitly control how routes are calibrated, the LRS uses a calibration point feature class.

Calibration points are point features that store measure values, route references, and network IDs. The combination of these three items constitutes a linear referencing method (LRM). LRMs are created by applying calibration points to routes to create an LRS Network.

The LRS is comprised of the following feature classes and tables:

• Centerline—The polyline feature class that stores route geometry.
• Centerline Sequence—The cross-reference table that manages the relationship between centerlines and routes.
• Calibration Point—The point feature class that stores route measure values.
• Redline—The polyline feature class that stores markup features for communicating LRS changes.

Note:

These feature classes and tables, with all necessary fields, can be generated automatically using the LRS setup wizard.

Centerline feature class

The centerline feature class provides a single source of geometry for all of the LRS Networks you build in an LRS.

Every feature in the centerline feature class represents a single unit of the highway. These can be used to represent a one-to-one relationship with routes or be combined to form larger routes.

Note:

The tolerance and resolution settings of the centerline feature class are propagated to the networks, intersections, and event feature classes registered with ArcGIS Roads and Highways . The spatial reference, x,y-tolerance and resolution, and z-tolerance and resolution of the centerline feature class must match that of the source routes used to load data into your LRS.

Note:

The centerline feature class must be z- enabled.

The LRS requires that the centerline feature class have a centerline ID field.

Field	Data type	Length	IsNullable	Description
Centerline ID	GUID		Yes	Unique ID for the centerline geometry

Note:

The CenterlineID field is a system-maintained field that is autopopulated by ArcGIS referencing tools. This field should not be edited manually.

Centerline sequence table

The many-to-many relationship between routes and centerlines is maintained through a cross-reference table known as the centerline sequence table. Since route IDs are not unique in the LRS, the centerline sequence table also contains a reference to the network ID field of the LRS Network. The combination of the network ID and route ID creates a way of uniquely identifying each route in the LRS. The use of the network ID helps differentiate between LRMs, as route IDs may not be unique across networks.

One centerline feature can participate in many routes, and a route can be comprised of more than one centerline. The centerline sequence table must have at least one record for each centerline-network combination.

The minimum fields for the centerline sequence table are as follows:

Field	Data type	Length	IsNullable	Description
Centerline ID	GUID		Yes	The unique ID for the centerline geometry.
FromDate	Date	8	Yes	The date that the portion of the centerline becomes active.
ToDate	Date	8	Yes	The date that the portion of the centerline is retired.
RouteId	String		Yes	The unique ID for the route.
NetworkId	Short Integer	5	Yes	The unique ID for the LRS network in which each route participates.

Note:

Records in the centerline sequence table should not be edited manually.

Note:

The NetworkID field is registered with the dLRSNetworks coded value domain when the LRS is created.

Calibration point feature class

Route measures are assigned to routes in the network using the calibration point feature class. Routes are calibrated by calculating an interpolated distance between any two calibration points along the route. Calibration points are specific to an LRS Network and make up the measure component of the LRM. Calibration point rules are as follows:

• There is only one calibration point feature class for all LRS networks registered with the LRS.
• A minimum of two calibration points is required for each route.
• Calibration points should be monotonic, meaning strictly increasing or decreasing in measure along a route. Nonmonotonic routes will calibrate but can result in undefined event locations and event behavior.
• Add a calibration point to a particular location to maintain a specific measure value.

Note:

The calibration point feature class should have the same spatial reference, x,y- and z-tolerance, and resolution as the centerline feature class.

The calibration point feature class must be z-enabled and cannot be m-enabled.

The minimum fields for the calibration point feature class are as follows:

Field	Data type	Length	IsNullable	Description
Measure	Double	8	Yes	The measure value stored for routes in an LRS Network.
From Date	Date	8	Yes	The date that the calibration point becomes active.
To Date	Date	8	Yes	The date that the calibration point is retired.
Route ID	String	255	No	The unique ID for the route.
Network ID	Short Integer	5	Yes	The unique ID for the LRS Network.

Note:

The NetworkID field is registered with the dLRSNetworks coded value domain when the LRS is created.

Tools are provided to help generate and update calibration points, as well as to detect nonmonotonic calibration on your routes.

Redline feature class

The redline feature class contains the basic information required to perform many of the route editing functions available in ArcGIS Roads and Highways. This markup feature is a placeholder for a future route editing operation used to alert an LRS Editor to necessary changes.

Note:

The redline feature class should have the same spatial reference and x,y-tolerance and resolution as the centerline feature class.

The redline feature class must be z-enabled and cannot be m-enabled.

The minimum fields for the redline feature class are as follows:

Field	Data type	Length	IsNullable	Description
From Measure	Double	8	Yes	The starting measure of the alignment change.
To Measure	Double	8	Yes	The ending measure of the alignment change.
Route ID	String	255	No	The unique ID for the target route.
Route Name	String	38	Yes	The name for the route.
Effective Date	Date	8	Yes	The date that the route change becomes effective. This date is applied to events affected by the change if the effective date applies.
Activity Type	Short Integer	5	Yes	The edit activity that should be made, such as Extend Route.
Network ID	Short Integer	5	Yes	The unique ID of the LRS Network.

Note:

The NetworkId field is registered with the dLRSNetworks coded value domain, and the ActivityType field is registered with the dActivityType coded value domain when the LRS is created.

Redline features can be entered as specifically or generally. It is expected that a GIS analyst will verify the redline feature and ensure that accurate geometry is entered into the database. A roughly sketched redline indicates that a change to the LRS is required and provides its general location.

Network feature class

The network feature class contains the route features used in the LRS. These routes have attributes, geometry from the centerline feature class, and calibration from the calibration point feature class.

Combined, these elements constitute a route in the LRM that can be used to locate events on that route. Each route should have a unique route identifier, called a route ID. The route ID can be a single field or a concatenation of multiple fields. If the network will use a concatenated route ID, all of the fields that comprise the route ID must be present in the network feature class, in addition to the RouteId field.

The route ID field data should be consistent throughout networks, events, calibration point feature classes, and the centerline sequence feature table.

Note:

If the network feature class is modeled before the LRS is created, ensure that the x,y- and z-tolerances and resolutions match those of the centerline feature class. The m-tolerance and resolution for the network is based on the units of measure of the spatial reference for the network feature class and the units of measure for the LRM being used. If the units of measure are the same, the m-tolerance and resolution match the x,y-tolerance and resolution. If the units of measure are different, you need to convert the x,y-tolerance and resolution to the corresponding m-tolerance and resolution.

For example, if your network feature class has a spatial reference in meters, with an x,y-tolerance of 0.001 meters and x,y resolution of 0.0001 meters. If the units of measure for the LRM are in meters, then the m-tolerance would be 0.001 and the m-resolution would be 0.0001. However, if the units of measure for the LRM are in kilometers, the x,y-tolerance and resolution values would need to be converted from meters to kilometers for the m-tolerance and resolution. In this example, the m-tolerance would be 0.000001 and the resolution would be 0.0000001.

The minimum fields for the network feature class are as follows:

Field	Data type	Length	IsNullable	Description
From Date	Date	8	Yes	The date that the portion of centerline becomes an active part of the route.
To Date	Date	8	Yes	The date that the portion of centerline becomes a retired part of the route.
Route ID	String	255	No	The unique ID for the route.

Note:

The network feature class fields should not be directly edited. They are maintained by Location Referencing.

The following fields must be configured if using a multifield route ID composed of several other fields in the network feature class:

Field	Data type	Length	IsNullable	Description
Fields that comprise the routeID field.	String, Short Integer, and Long Integer	Less than or equal to the RouteId field length	Yes	The fields that comprise the concatenated route ID for the network. Each field should be modeled separately in the network feature class.

Events

Learn more about the events data model

Learn more about creating an LRS intersection class.