LRS data model

Disponible avec la licence Location Referencing.

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. Measures on routes are what the LRS uses to display event layers 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.

Remarque :

Feature classes and tables will be created with all necessary fields when running the Create LRS tool.

Feature dataset requirement

To support service-based editing of your data in Pipeline Referencing, certain feature classes in the LRS data model must reside in a feature dataset in your geodatabase. If the feature classes and tables are modeled in advance, the following feature classes must be contained in a feature dataset: Centerline, Calibration Points, Redline, Networks, Events, and Intersections.

Remarque :

• If you use the Create LRS tool to create your LRS and minimum schema items, these required feature classes are automatically placed in a feature dataset.
• If the LRS was created using ArcMap or ArcGIS Pro 2.2 or earlier, you need to move these feature classes into a feature dataset and run the Modify LRS tool to edit the LRS in ArcGIS Pro 2.3 or later.

Version Management requirement

LRS data you publish as a service must be branch versioned and the version management capability must be enabled when it is published as a service.

All LRS feature classes and tables must have the additional fields required for version management, such as GlobalIDs, added before publishing.

Learn more about registering a dataset using branch versioning requirements

Learn more about publishing with linear referencing and version management

LRS dataset

A linear referencing system (LRS) dataset is a feature dataset containing all the LRS feature classes.

Remarque :

You can view the hierarchy for an LRS from either the Contents or Catalog panes.

The following tools create an LRS dataset, as of ArcGIS Pro 2.3:

• Create LRS —The newly created centerline, calibration point, and redline feature classes will be created inside a feature dataset with the same name as the provided LRS name.
• Create LRS From Existing Dataset —The existing centerline, calibration point, and redline feature classes that are not yet registered with an LRS must be inside a common feature dataset. The feature dataset name can be different from the LRS name.
• Modify LRS —The existing centerline, calibration point, and redline feature classes that are registered with an LRS must be inside a common feature dataset. The feature dataset name can be different from the LRS name.

The LRS dataset is required to run the following tools:

• All Configuration toolset tools
• Append Events
• Append Routes
• Apply Event Behaviors
• Delete Routes
• Derive Event Measures
• Generate Calibration Points
• Generate Events
• Generate Intersections
• Generate Routes
• Remove Overlapping Centerlines

Some of the information contained in the LRS controller dataset can be read by using an arcpy.Describe function. To read the LRS metadata and event behavior rules for a geodatabase with an LRS controller dataset, use the following functions:

FileGDB:

desc = arcpy.Describe("C:\\Data\\LRData\\LrsSchema.gdb\\Lrs\\Lrs")

          lrsXML = desc.lrsMetadata

          eventBehaviors = desc.eventBehaviorRules

SDE:

desc = arcpy.Describe("C:\\Data\\LRData\\LrsSchema.sde\\GPRefresh.DBO.LRS\\GPRefresh.DBO.LRS")

          lrsXML = desc.lrsMetadata

          eventBehaviors = desc.eventBehaviorRules

Writing to a file:

txtFile = open("C:\\Data\\LRData\\lrsXML.xml", "w")

          txtFile.write(lrsXML)

          txtFile.close()

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 pipe. These can be used to represent a one-to-one relationship with routes or be combined to form larger routes.

Remarque :

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

Remarque :

The centerline feature class must be z- enabled.

The LRS requires that the centerline feature class have a centerline ID field. The Create LRS and Create LRS From Existing Dataset tools provide the opportunity to map a centerline ID field.

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

Remarque :

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 will be retired.
RouteId	String or GUID	38 or greater	Yes	The unique ID for the route.
NetworkId	Short Integer	5	Yes	The unique ID for the LRS network in which each route participates.

Remarque :

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

Remarque :

The NetworkID field will be 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 could result in undefined event locations and event behavior.
• Add a calibration point to a particular location to maintain a specific measure value.

Remarque :

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 will be retired.
Route ID	String or GUID	Same type and length as the RouteID field in the centerline sequence table	No	The unique ID for the route.
Network ID	Short Integer	5	Yes	The unique ID for the LRS Network.

Remarque :

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

Use the Generate Calibration Points tool to generate calibration points.

Redline feature class

The redline feature class contains the basic information required to perform many of the route editing functions available in Pipeline Referencing. The redline feature can be thought of as a placeholder for a future route editing operation. It is used as a markup feature so that LRS users do not have to be LRS maintainers. It can be disruptive to a user's workflow to discover differences between the LRS and the real world. Instead of stopping work and waiting for the LRS to be updated, users can enter a redline feature into the geodatabase to indicate where the route should be, notify the GIS team, and continue working with the event data.

Remarque :

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 or GUID	Same type and length as the Route ID field in the centerline sequence table	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. The date will be applied to events affected by the change.
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.

Remarque :

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

Redline features can be entered as accurately or as generally as you like. 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 a 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 field data should be consistent throughout networks, events, calibration point feature classes, and the centerline sequence feature table.

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

Remarque :

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 will be 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 will be the same as 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, suppose 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 or GUID	Same type and length as the RouteId field in the centerline sequence table	No	The unique ID for the route.
Route Name	String	255	No	The unique name for the route.

Remarque :

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

The following fields should be configured if creating an LRS Network that supports lines, such as an Engineering Network:

Field	Data type	Length	IsNullable	Description
Route Name	String	100 or greater	Yes	The name of the route
Line ID	String or GUID	Same type and length as the Route ID field in the centerline sequence table	Yes	The unique ID for the line
Line Name	String	Same length as Route Name field	Yes	The name of the line
Line Order	Long		Yes	The order of the route within the line

Events

Learn more about the events data model

Learn more about creating an LRS intersection class.