The Add Line Event widget allows you to create line events along routes in a linear referencing system (LRS). You can use the widget to manage pipeline data with ArcGIS Pipeline Referencing and roadway data with ArcGIS Roads and Highways. You can represent characteristics of a route, such as operating pressure for a pipeline or lane information for a road, as line events.
Note:
All Location Referencing widgets support express mode. When you create an app in express mode, all Location Referencing widgets are automatically configured based on the web map added to the Map widget. Any modifications made in the Map widget, such as changing the web map, will instantly be reflected in the Location Referencing widgets. Express mode allows you to efficiently set up Location Referencing widgets within ArcGIS Experience Builder, streamlining the deployment process for apps that contain Location Referencing widgets.
Examples for Pipeline Referencing
Use this widget to support app design requirements such as the following:
- Add inspection notes information for a pipe that is under maintenance.
- Add a new event feature and retire the overlapping section of a previous feature.
- Add operating pressure and DOT Class information in one editing session.
- Add inspection range event data based on coordinates collected by field operators.
- Add consequence segment information for a pipeline segment by specifying the start and end offsets from two known reference points.
Examples for Roads and Highways
Use this widget to support app design requirements such as the following:
- Add lane information for a freeway.
- Add a new median to a route and retire the overlapping section of the previous median.
- Add parking and access control information in one editing session.
- Add road closure event data based on coordinates collected by first responders.
- Add guardrail information for a highway segment by specifying the start and end offsets from two bridge points.
Usage notes
This widget requires connection to a Map widget. To add line events, the Map widget must be connected to a web map data source with an LRS published with the Linear Referencing and Version Management capabilities enabled.
To create an LRS and publish a feature service with the Linear Referencing and Version Management capabilities enabled, complete the steps in the following ArcGIS Pro documentation:
- Pipeline Referencing—Create the LRS, networks, events, and intersections and Share as web layers
- Roads and Highways—Create the LRS, networks, events, and intersections and Share as web layers
To use the Add Line Event widget with a feature service published to ArcGIS Enterprise, you must be signed in with an ArcGIS Enterprise account.
When using this widget in an app, if a message about acquiring locks appears, it means that conflict prevention is enabled.
Learn more about conflict prevention in Pipeline Referencing
Learn more about conflict prevention in Roads and Highways
When you include this widget in an app, a panel provides users with the following parameters for adding a line event:
- Type—Add single or multiple line events.
- Single Line—Add a single line event.
- Multiple Line—Add multiple line events in one edit activity.
- Event (appears when you specify Single Line for Type)—Choose the event layer from which to add a line event.
- Network—This parameter lists the network layer that is associated with the line event layer.
- Attribute Set (appears when you specify Multiple Line for Type)—Attribute sets are collections of event layer attributes. If a feature service is configured with attribute sets for Pipeline Referencing or attribute sets for Roads and Highways, you can choose one from the drop-down menu. The widget only displays line events that are part of the attribute set. You can use attribute sets to create multiple events with a set of additional, organization-specific attributes in a single edit.
- From Method—The method the widget uses to specify the starting location of the line events to be added is listed here.
- Route and Measure—Specify the starting location of the added line event using a specific measure along a route.
- From Route ID or From Route Name—Provide the route ID or name of the route you want to use to define the line event starting point. If the network layer has route name configured as an identifier, this parameter is labeled From Route Name.
- From Measure—Provide a measure value for the line event starting point. The measure value defines the exact location on the route where the line event starts. The label for this parameter also displays the unit of measure defined by the network layer. For example, if the unit of measure is meters, this parameter is labeled From Measure (Meters) at run time.
- Coordinate—Specify the starting location of the added line event using x-, y-, and z-coordinates.
- From Route ID or From Route Name—Provide the name of the route you want to use to define the line event starting point. If the network layer has route name configured as an identifier, this parameter is labeled From Route Name.
- X Coordinate—Provide the x-coordinate.
- Y Coordinate—Provide the y-coordinate.
- Z Coordinate—Optionally, provide the z-coordinate.
- From Measure—This parameter notes the nearest measure to the input coordinates. The label for this parameter also displays the unit of measure defined by the network layer. For example, if the unit of measure is meters, this parameter is labeled From Measure (Meters) at run time.
- Distance—This parameter notes the distance between the input coordinates and the nearest measure. The label for this parameter also displays the unit of measure defined by the network layer. For example, if the unit of measure is meters, this parameter is labeled Distance (Meters) at run time.
- Location Offset—Specify the starting location of the added line event using an offset distance from an intersection, LRS point event, or a non-LRS point feature.
- From Route ID or From Route Name—Provide the name of the route you want to use to define the line event starting point. If the network layer has route name configured as an identifier, this parameter is labeled From Route Name.
- Referent—Provide the point layer that the line event starting point will be offset from.
- Offset Feature—Provide the point feature that the line event starting point will be offset from.
Note:
The name of the parameter below the Referent parameter is dependent on the field configured in the Configure Display Field setting.
- Offset—Provide the distance the line event starting point will be from the offset feature.
- Route and Measure—Specify the starting location of the added line event using a specific measure along a route.
- To Method—The method the widget uses to specify the ending location of the line events to be added is listed here.
- Route and Measure—Specify the ending location of the added line event using a specific measure along a route.
- To Route ID or To Route Name—Provide the route ID or name of the route you want to use to define the line event ending point. If the network layer has route name configured as an identifier, this parameter is labeled To Route Name. This parameter is only available when either the chosen event layer is a spanning line event or the chosen attribute set includes a spanning line event layer.
- To Measure—Provide a measure value for the line event ending point. The measure value defines the exact location on the route where the line event ends. The label for this parameter also displays the unit of measure defined by the network layer. For example, if the unit of measure is meters, this parameter is labeled To Measure (Meters) at run time.
- Coordinate—Specify the ending location of the added line event using x-, y-, and z-coordinates.
- To Route ID or To Route Name—Provide the name of the route you want to use to define the line event ending point. If the network layer has route name configured as an identifier, this parameter is labeled To Route Name.
- X Coordinate—Provide the x-coordinate.
- Y Coordinate—Provide the y-coordinate.
- Z Coordinate—Optionally, provide the z-coordinate.
- To Measure—This parameter notes the nearest measure to the input coordinates. The label for this parameter also displays the unit of measure defined by the network layer. For example, if the unit of measure is meters, this parameter is labeled To Measure (Meters) at run time.
- Distance—This parameter notes the distance between the input coordinates and the nearest measure. The label for this parameter also displays the unit of measure defined by the network layer. For example, if the unit of measure is meters, this parameter is labeled Distance (Meters) at run time.
- Location Offset—Specify the ending location of the added line event using an offset distance from an intersection, LRS point event, or a non-LRS point feature.
- To Route ID or To Route Name—Provide the name of the route you want to use to define the line event ending point. If the network layer has route name configured as an identifier, this parameter is labeled To Route Name.
- Referent—Provide the point layer that the line event ending point will be offset from.
- Offset Feature—Provide the point feature that the line event ending point will be offset from.
Note:
The name of the parameter below the Referent parameter is dependent on the field configured in the Configure Display Field setting.
- Offset—Provide the distance the line event ending point will be from the offset feature.
- Route and Measure—Specify the ending location of the added line event using a specific measure along a route.
- Start Date—Specify the start date of the event or events.
- End Date—Specify the end date of the event or events.
- Merge coincident events—Merge edited events that have exactly the same attributes as an existing event and are adjacent to or overlapping that existing event in terms of measure values.
- Retire overlapping events—Retire existing events that overlap with the new events.
- Add event to dominant route—Add events to the dominant route where route concurrencies exist.
Settings
The Add Line Event widget includes the following settings:
- Mode—Choose a method of loading data.
- Select Layers—Select a Map widget and load all layers from the web map.
- Select a Map widget—Select a Map widget on the page that's connected to a web map.
- Load layers—Load layers from the web map in the connected Map widget. To load layers, the Map widget must be connected to a web map that contains LRS layers.
- Clear layers—Remove all loaded layers from the widget.
- Layers—After loading layers, you can click the down arrow to expand the list of layers. Click a layer to open the Layer Configuration panel.
- Layer Configuration—Configure settings for individual layers.
- LRS Network:
- Label—Provide a meaningful label for the layer. This label appears in the widget panel at run time.
- LRS intersection layers, LRS point event layers, LRS calibration point layer, and non-LRS point layers:
- Label—Provide a meaningful label for the layer. This label appears in the widget panel at run time.
- Configure Display Field—Choose a field to be displayed as the name of the parameter below the Referent parameter when adding line events using the Location Offset method.
- LRS line event layers:
- Label—Provide a meaningful label for the layer. This label appears in the widget panel at run time.
- Use Field Alias—Turn on this setting to display field aliases at run time. An alias, or display name, is an alternative name for a field. It is usually a more user-friendly description of the content of the field. Unlike true field names, aliases do not have to adhere to the limitations of the database, so they can contain special characters such as spaces.
- Configure Fields—Choose the attribute fields from the layer to include in the widget panel at run time. You can define whether each attribute field is editable at run time by clicking Editable or Not editable.
Note:
The settings you define for Configure Fields only apply when the user is adding a single line event. For multiple line events, fields display if they are included in the attribute set the user chooses at run time.
- LRS Network:
- Interact with a Map widget—Connect the Add Line Event widget to a Map widget. Any web maps in the connected Map widget appear in the list. After connecting to a Map widget, you can click the down arrow next to the Select Layers button
to expand the list of layers. Click a layer to open the Layer Configuration panel. - Layer Configuration—Configure settings for individual layers. Review the settings available in the Layer Configuration panel.
- Select Layers—Click the Select Layers button to open the Select Layers panel. You can select or unselect layers from the list in the panel.
- Select Layers—Select a Map widget and load all layers from the web map.
- Default Settings—Configure the default settings that you want available in the widget when it first loads.
- Event (Single Line)—Choose the default event layer for adding a single line event.
- Network (Multiple Line)—Choose the default network layer for adding multiple line events. When the user is adding a single line event, the network is always the registered network for the selected event layer.
- From Method—Choose the default method to add the line event's starting location.
- Route and Measure—The widget specifies the location of added line events using the route name and measure value that the user provides.
- Coordinate—The widget specifies the location of added line events using the x-, y-, and z- coordinates that the user provides.
- Location Offset—The widget specifies the location of the added line event using an offset distance from an intersection, LRS point event, or a non-LRS point feature.
- To Method—Choose the default method to add the line event's ending location.
- Route and Measure—The widget specifies the location of added line events using the route name and measure value that the user provides.
- Coordinate—The widget specifies the location of added line events using the x-, y-, and z- coordinates that the user provides.
- Location Offset—The widget specifies the location of the added line event using an offset distance from an intersection, LRS point event, or a non-LRS point feature.
- Type—Choose whether the widget is set to add single events or multiple events.
- Attribute Set—If a layer is configured with attribute sets for Pipeline Referencing or attribute sets for Roads and Highways, you can choose a default attribute set from the drop-down menu. The widget only displays line events that are part of the attribute set. Attribute sets are collections of event layer attributes. You can use attribute sets to create multiple events with a set of additional, organization-specific attributes in a single edit.
- Display Settings—Choose the settings to display in the widget panel at run time. If you choose to hide a setting here, the widget settings you configure for Default Settings are unchangeable by the user at run time.
- Hide Type—Hide the Type setting from the widget panel.
- Hide Event—Hide the Event setting from the widget panel.
- Hide Network—Hide the Network setting from the widget panel.
- Hide Method—Hide the From Method and To Method settings from the widget panel.
- Hide Attribute Set—Hide the Attribute Set setting from the widget panel.
- Hide Measures—Hide the From Measure and To Measure settings from the widget panel.
- Coordinate Settings—Configure settings related to the Coordinate method.
- Spatial Reference Type—Set a spatial reference for the Coordinate method. You can use the spatial reference from the web map or from the LRS layers.
- Search Units—Choose the unit of measure the distance will be displayed in. The distance is how far from the selected route the input coordinate is. This setting also determines the unit of measurement for the search radius.
- Radius—Set the maximum distance for the search radius. The search radius is the maximum distance the input coordinate can be from a route.
Note:
If the coordinate is not within the search radius, the No routes found with provided coordinate error message appears in the widget panel.
- Location Offset Settings—Configure settings related to the Location Offset method.
- Default Referent—Choose the default referent layer to be displayed in the Referent parameter.
- Default Offset Units—Choose the unit of measure for the Offset parameter.
- Concurrency Settings—Choose the settings for adding events to the dominant route in the widget panel at run time.
- Hide Add to Dominant Route Option—Hide the Add event to dominant route option from the widget panel.
- Enable Add to Dominant Route Option—Enable the Add event to dominant route option in the widget panel.
- Don't allow override of event placement on dominant routes—Turn on this setting to allow the user to add events to the dominant route by default.
Add a line event
To add a line event, complete the following steps:
- Start Experience Builder, and sign in to an ArcGIS Enterprise portal.
- Add a Map widget, and connect it to a web map with LRS data published with the Linear Referencing and Version Management capabilities enabled.
- Add an Add Line Event widget, connect it to the Map widget, and load LRS layers from the Map widget.
- Publish the app.
- Launch the app, and, if prompted, sign in to your ArcGIS Enterprise portal.
- Zoom to the location where you want to add a line event.
Note:
To zoom to route locations, you can use the Search By Route widget or use data actions with the Search By Route widget or Table widget. - Open the Add Line Event widget.
The first image is an example of the Add Line Event widget panel with Pipeline Referencing data. The second image is an example of the Add Line Event widget panel with Roads and Highways data. Tip:
You can also use data actions to add line events.
- Use the default type, or click the Type drop-down arrow and change the type if necessary.
- If Type is set to Single Line, use the default line event layer, or click the Event drop-down arrow and choose another line event layer.
If Type is set to Multiple Line, use the default attribute set or choose another attribute set.
The value that appears for the Network parameter is based on the chosen event layer.
- If there are multiple methods configured in the widget settings, choose one of the following options from the From Method drop-down menu:
- Route and Measure
- Coordinate
- Location Offset
- If you chose Route and Measure in step 10, complete the following steps to add the line event's starting location:
- Specify the starting location for the line event by doing one of the following:
- Provide a route ID or name in the From Route ID or From Route Name text box.
- Click the route picker
, and click a route on the map.
The From Measure value is populated based on the location you click. Once you provide a start measure value, a green point appears at that location on the map.
- Optionally, change the start measure value by doing one of the following:
- Provide a measure value in the From Measure text box.
Note:
Stationing measure values are also supported.
- Click the measure picker , and click a point along the route.
- Check the Use route start measure check box.
- Provide a measure value in the From Measure text box.
- Specify the starting location for the line event by doing one of the following:
- If you chose Coordinate in step 10, complete the following steps to add the line event's starting location:
- Specify the starting location for the line event by doing one of the following:
- Provide a route ID or name in the From Route ID or From Route Name text box.
- Click the route picker , and click a route on the map.
- Leave the From Route ID text box blank and proceed to the next step.
Note:
Once valid values are provided in the X Coordinate, Y Coordinate, and Z Coordinate (optional) text boxes, the nearest route’s route ID populates the From Route ID text box.
- Specify a location for the start measure of the line event by providing values in the X Coordinate and Y Coordinate text boxes. Optionally, provide a value in the Z Coordinate text box.
Note:
Do not include commas in the coordinate value.
- Specify the starting location for the line event by doing one of the following:
- If you chose Location Offset in step 10, complete the following steps to add the line event's starting location:
- Specify the starting location for the line event by doing one of the following:
- Provide a route ID or name in the From Route ID or From Route Name text box.
- Click the route picker , and click a route on the map.
- Choose a referent layer from the Referent drop-down menu.
- For the parameter below the Referent parameter, specify an offset feature by doing one of the following:
- Provide an attribute in the text box based on the referent layer's display field.
- Click the route picker , and click an offset feature on the map.
- Specify an offset distance in the Offset text box.
Note:
A negative Offset value places the measure location opposite the direction of calibration from the selected offset feature.
- Specify the starting location for the line event by doing one of the following:
- If there are multiple methods configured in the widget settings, choose one of the following options from the To Method drop-down menu:
- Route and Measure
- Coordinate
- Location Offset
- If you chose Route and Measure in step 14, complete the following steps to add the line event's ending location:
- Specify the ending location for the line event by doing one of the following:
- For events on a nonline network or nonspanning events on a line network, click the measure picker , and click the point on the route where you want the line event to end.
The To Route ID or To Route Name parameter value defaults to the From Route ID or From Route Name parameter value and cannot be changed. If you need to change the To Route ID or To Route Name parameter value, provide a new route ID or name in the From Route ID or From Route Name parameter text box
- For spanning events on a line network, accept the default name for the To Route Name parameter, or change the ending route by providing another route name in the To Route Name text box.
Alternatively, click the route picker
, and click the point on the route where you want the line event to end.Note:
The From Route and To Route values must be on the same line.
Once you provide an end measure value, a red point appears at that location on the map.
- For events on a nonline network or nonspanning events on a line network, click the measure picker
- Optionally, specify a new end measure value by doing one of the following:
- Provide a measure value in the To Measure text box.
Note:
Stationing measure values are also supported.
- Click the measure picker , and click the measure value along the route on the map.
- Check the Use route end measure check box.
- Provide a measure value in the To Measure text box.
- Specify the ending location for the line event by doing one of the following:
- If you chose Coordinate in step 14, complete the following steps to add the line event's ending location:
- Specify the ending location for the line event by doing one of the following:
- For events on a nonline network or nonspanning line events on a line network, the To Route ID or To Route Name parameter value defaults to the From Route ID or From Route Name parameter value and cannot be changed. If you need to change the To Route ID or To Route Name parameter value, provide a new route ID or name in the From Route ID or From Route Name parameter text box.
- For spanning events on a line network, accept the default name for the To Route Name parameter, or change the ending route by providing another route name in the To Route Name text box.
- Specify a location for the end measure of the line event by providing values in the X Coordinate and Y Coordinate text boxes. Optionally, provide a value in the Z Coordinate text box.
Note:
Do not include commas in the coordinate value.
- Specify the ending location for the line event by doing one of the following:
- If you chose Location Offset in step 14, complete the following steps to add the line event's ending location:
- Specify the ending location for the line event by doing one of the following:
- For events on a nonline network or nonspanning line events on a line network, the To Route ID or To Route Name parameter value defaults to the From Route ID or From Route Name parameter value and cannot be changed. If you need to change the To Route ID or To Route Name parameter value, provide a new route ID or name in the From Route ID or From Route Name parameter. text box
- For spanning events on a line network, accept the default name for the To Route Name parameter, or change the ending route by providing another route name in the To Route Name text box.
- Choose a referent layer from the Referent drop-down menu.
- Specify an offset feature by doing one of the following:
- Provide an attribute in the text box based on the referent layer's display field.
- Click the route picker , and click an offset feature on the map.
- Specify an offset distance in the Offset text box.
Note:
A negative Offset value places the measure location opposite the direction of calibration from the selected offset feature.
- Specify the ending location for the line event by doing one of the following:
- Specify the start date of the line event by doing one of the following:
- Leave the default start date, which is the current date.
- Provide a start date in the Start Date text box.
- Click the calendar button
, and choose a start date. - Check the Use route start date check box.
- Optionally, specify the end date of the line event by doing one of the following:
- Provide an end date in the End Date text box.
- Click the calendar button , and choose an end date.
- Check the Use route end date check box.
Note:
If you do not provide an end date, the event remains valid from the route start date into the future.
- Choose one of the following data validation options to prevent erroneous input while characterizing a route with line events:
- Merge coincident events—When all attribute values for a new event are exactly the same as an existing event, and if the new event is adjacent to or overlapping an existing event in terms of its measure values, and its time slices are coincident or overlapping, the new event is merged with the existing event and the measure range is expanded accordingly. For more information, refer to Merge coincident events scenario in ArcGIS Pipeline Referencing or Merge coincident events scenario in ArcGIS Roads and Highways.
- Retire overlapping events—The measure, start date, and end date of existing events are adjusted to prevent overlaps with respect to time and measure values once the new line event or events are created. For more information, refer to Retire overlaps scenario in ArcGIS Pipeline Referencing or Retire overlaps scenario in ArcGIS Roads and Highways.
- Merge coincident events—When all attribute values for a new event are exactly the same as an existing event, and if the new event is adjacent to or overlapping an existing event in terms of its measure values, and its time slices are coincident or overlapping, the new event is merged with the existing event and the measure range is expanded accordingly. For more information, refer to Merge coincident events scenario in ArcGIS Pipeline Referencing or Merge coincident events scenario in ArcGIS Roads and Highways.
- Optionally, if route concurrencies exist, add line events to the dominant route.
Concurrent routes are routes that share the same centerlines. This relationship may exist to model two routes with different directions of calibration. Where these concurrent routes exist, you can use a set of rules to choose a route that's considered dominant.
For example, in the diagram below, there are three routes with route IDs of 100, 200, and 300.
The route dominance rule is set so that the lesser the route name, the more dominant the route. Using this condition, route 100 is the most dominant route, and routes 200 and 300 have the same order of dominance.
Section Description 1
Route 200 is the dominant route because no other route exists in this section; the event is added to route 200.
2
Route 100 has the greater order of dominance; the event is added to route 100.
3
Both route 200 and route 300 have the same order of dominance; the event is added to the route of your choice.
4
Route 200 is the dominant route because no other route exists in this section; the event is added to route 200.
Learn more about adding line events to the dominant route in Pipeline Referencing
Learn more about adding line events to the dominant route in Roads and Highways
- Click Next.
The attributes for the chosen line event layer appear in a second pane.
- Provide attribute values for the event layer.
Note:
- You can use the Copy Attributes tool
to copy attributes from an existing event. - When adding multiple events, the following apply:
- An attribute set can contain events registered with different networks. Only events registered with the selected network appear.
- Check or uncheck the check box next to each event layer to include or exclude it in the edit activity. Unchecked events will not be added.
- The visibility and editability of an event field is dependent on the configuration of the attribute set. The event configuration for single events does not apply when adding multiple events.
The first image is an example of the Add Line Event widget panel with Pipeline Referencing data. The second image is an example of the Add Line Event widget panel with Roads and Highways data. - You can use the Copy Attributes tool
- Click Save.
A confirmation message appears in the widget panel once the new line event is added and appears on the map.
Interaction options
You can use data actions in other widgets to launch the Add Line Event widget and populate associated values. To use data actions, the network in the source widget must have associated line events, the data action options of Add Line Event in the source widget must be turned on, and the Add Line Event widget must be configured in the app.
The following widgets support data actions of the Add Line Event widget:
- Search By Route widget—Data action populates the event or attribute set, network, route, measure, and date options.
- Table widget—Data action populates the event or attribute set, network, route, and date options.
- LRS Identify widget—Data action populates the event or attribute set, network, route, measure, and date options.
Note:
You can change any values after they are populated. If you do, the Add Line Event widget still validates all entries.
Run data actions with the Search By Route widget
To use the data action at run time with the Search By Route widget, complete the following steps:
- Select a route in the Search By Route results.
- Click the Actions button at the top of the Search By Route widget panel.
- Add a line event by doing one of the following:
- If the search result contains a route with start and end measure values, click Add Line Event.
- If the search result contains a route with a single measure value, click Add Line Event (from) to be the start measure or Add Line Event (to) to be the end measure of the line event to be added.
If you chose Add Line Event (from), the From Measure value is populated, and you must provide a To Measure value.
If you chose Add Line Event (to), the To Measure value is populated, and you must provide a From Measure value.
The parameters are populated based on the selected route from the Search By Route widget.
- If the search result contains a route with start and end measure values, click Add Line Event.
Run data actions with the Table widget
To use the data action at run time with the Table widget, complete the following steps:
- For a nonline network, complete the following steps:
- Select a route from the network layer in the Table widget.
- Click the Actions button at the top of the Table widget panel.
- Click Add Line Event.
The From Route Name or From Route ID and To Route Name or To Route ID parameters are populated based on the route you select. You must populate the measure values to add the events.
- For a line network, complete the following steps:
- Select one or two routes on the same line from the network layer in the Table widget.
- Click the Actions button at the top of the Table widget panel.
- Click Add Line Event.
The From Route Name or From Route ID and To Route Name or To Route ID parameters are populated based on the route you select. You must populate the measure values to add the events.
If two routes are selected for a spanning event or events in an attribute set, they populate the From Route Name or From Route ID and To Route Name or To Route ID parameters according to their line order. You must populate the measure values to add the events.
The Start Date and End Date parameters are populated with the start and end dates of the selected route or with the dates of the route with the lower line order if two routes are selected.
Run data actions with the LRS Identify widget
To use the data action at run time with the LRS Identify widget, complete the following steps:
- Click a specific location on a route using the LRS Identify widget.
- Click the Actions button at the top of the LRS Identify widget panel.
- Do one of the following:
- Click Add Line Event (from).
- Click Add Line Event (to).
If you chose Add Line Event (from), the From Measure parameter is populated, and you must provide a To Measure value.
If you chose Add Line Event (to), the To Measure parameter is populated, and you must provide a From Measure value.
The parameters are populated based on the route and location from the LRS Identify widget.