Available with Location Referencing license.
ArcGIS Roads and Highways can persist referent locations and measures with events, in addition to the route ID and measures. This is particularly useful for capturing the original location method for an event as well and using the referent offset, instead of the route and measure, to locate events that are impacted by a cartographic realignment.
In the scenario below, cartographic realignment is performed on a segment of Route1 between Intersection1 and Intersection2.
The route edit impacts two events differently according to the following event location methods used to store their measures:
- Event location saved as route and measure—Measures remain intact after the edit although the measure length of the route increases and the resulting event does not touch Intersection 2. The event location changes relative to Intersection 2.
- Event location saved as referent and offset—Measures change after the edit according to their relation to stored referent and offset values. The location of the intersections remains intact and the resulting event is still located between Intersection 1 and Intersection 2.
The following image shows how a realignment impacts an event whose location is saved using route and measure (black line) differently than an event whose location is stored using referent and offset (green line):
Referent locations can be stored using the following techniques:
- Offset distance from any point feature in the geodatabase
- Offset distance from a intersection point feature
- Offset distance from a point event feature
- Offset distance from an x,y coordinate
- Offset distance from a station
To use referent and offset information, additional columns must be configured in the event layer for the referent method, the referent location, and the referent offset. For line events, there are two sets of these columns, one for the from measure and one for the to measure, as shown in the table below. For point events, only one set of the new columns is required.
Learn more about event referent fields in the Roads and Highways events data model
Once these columns are added, they can be enabled in the event using the Enable Referent Fields tool.
Once referents are configured and enabled for an LRS Event, the Honor Referent Location event behavior can be configured for cartographic realignment in the Modify Event Behavior Rules tool.
| From Measure | From Ref Method | From Ref Location | From Ref Offset | To Measure | To Ref Method | To Ref Location | To Ref Offset |
|---|---|---|---|---|---|---|---|
0.26 | Intersections | {-6E5F} | 10 | 0.43 | Intersections | {-6E5F} | -26.2 |
0 | Intersections | {-6928} | 0 | 2.359 | X/Y | 468465.683, 361690.902 | 100 |
0.41 | Stations | 5 | -134.682 | 0.68 | Stations | 5 | 1+38.998 |
0 | Posts | 11 | -20 | 1 | Length | 6336 |
Event referent fields
The properties of the manually added referent and offset columns in an event layer are described in the remaining sections.
Referent method
This column stores the methodology provided for referencing the event location. In addition, events in the same layer can have different referent methods. For example, an event in the layer can be located by x,y coordinate offset and another event in the same event layer can be located by intersection and offset.
The referent method information is stored in a coded value domain named dReferentMethod in the geodatabase. This domain is created automatically when the LRS is created and has the following default values:
- Code 0 for x,y location offset
- Code 1 for length distance from a point location
- Code 2 for stationing offset
The rest of the coded values are added automatically when you add a network, register a line or point event, create an LRS intersection class, or add a stationing event.
Note:
- If you want to offset an event from a point feature class that is not part of the LRS (but present in the geodatabase), you need to manually add that feature class's code and description (name) into the dReferentMethod domain.
- You can access the domains by right-clicking the geodatabase, clicking Properties > Domains, and clicking the dReferentMethod domain.
A coded value is used to store the referent method versus saving the name of the feature class used for the referent feature. In this manner, if the name of the feature class is changed, the event data doesn't need to be updated.
Referent location
This column stores the referent location information for locating the feature. The following table describes the type of information stored in this field:
| If the referent method is | The referent location field stores |
|---|---|
Route ID and Measure | Measure |
Intersection and Offset | Intersection ID Note:The intersection ID used as a referent location must be on the same route that the event is on. |
Event ID and Offset | Event ID |
Feature Class and Offset | Object ID Note:This must be set as the Display field for the feature class in the map service. |
X,Y Coordinates | Comma-separated coordinates |
A Station Measure (relative to a Station Event layer) | Referent station Event ID |
Starting Station and Offset | Referent station Event ID |
Referent offset
The Referent Offset column stores the offset measure from the referent location. The following table describes the type of information stored in this field:
| If the referent method is | The referent offset field stores |
|---|---|
Route ID and Measure | Measure |
Intersection and Offset; Event and Offset; X,Y Coordinates; or Feature Class and Offset | Offset as a negative or positive value (compass directions provided by the user are translated to + or – offsets at storage) |
A station measure (relative to a Station Event layer) or Starting Station and Offset | User-supplied station measure in the station format (for example, 100+22.65) |
The units of measure for storage are configured at the time of registering the event layer.