Time slicing routes
A time slice is the representation of a linear referencing system (LRS) feature during a specific time range. The shape and calibration of a route or event will likely change across time when using the editing tools in ArcGIS Pro or the ArcGIS Event Editor web application. ArcGIS Roads and Highways supports and maintains temporality via editing, representation, and analysis. This means that the From Date and To Date values will be accurately updated and stored for each point in time of the existence of an LRS feature.
Time slicing occurs because of changes in the shape of the route (realignment of the route), different calibration on the route (changes to the measured m-values), or both at different points in time. Time slicing routes is based on the date values in the calibration point feature class and the centerline sequence table that may exist due to realignment of the route. For example, the records in the calibration point feature class and centerline sequence shown below represent records of a route that has been realigned.
Look at the calibration point feature class first. Notice that the route IDs for all the calibration points are the same. The two calibration points at the ends, highlighted in yellow, take part in the calibration of the route starting January 1, 2012. Since the To Date value is set to <Null>, these calibration points will always take part in the calibration of the route after January 1, 2012.
After the realignment occurred on January 1, 2013, there are two more calibration changes to the m-values in the middle of the route, highlighted in turquoise, and the From Date value is set to January 1, 2013. Since the To Date value is set to <Null>, these calibration points will always take part in the calibration of the route starting January 1, 2013.
From the centerline sequence table, it is evident that there are four centerlines that provide the shape for the route in two time ranges: January 1, 2012 to January 1, 2013, and January 1, 2013 to infinity. A value of <Null> means there is no specific start or end date, and thus the representation of the feature extends from the beginning of time or to the end of time, respectively. It is also clear that Centerline A and Centerline C represent the same shape for both date ranges. Centerline B is the path of the route for the first date range, but starting January 1, 2013, the route was realigned to follow the path depicted by Centerline D.
To visualize the time slicing of a route, the route features must be generated. Route features are initially created when creating an LRS Network. You can also regenerate the shapes of an existing route feature. After the route features are created, two route features are created for the same route (RouteID) but with different date ranges, as shown below. Each route feature represents the calibration and shape based on the input calibration point and centerline that fall within the time range of the route. This process is called time slicing of routes, and this is required to support the temporal aspect of Roads and Highways.
Time slicing events
ArcGIS Roads and Highways provides temporal support to represent and edit routes that change with time by managing them as route features with a time stamp, thereby storing every version of the route. Similarly, any events associated with the route are also managed as event features with the appropriate time stamp to represent the changes in time.
The internal events are created by registering an event within the LRS geodatabase. During this process, if there is one event record in the source table with From Date and To Date values that span across multiple route features, after the registration of the internal event is complete, you will notice that there is more than one event feature created. The number of features created will be in sync with the number of route features available based on their temporal date ranges. Time slicing events is done to support the temporal aspect of Roads and Highways and to ensure that event behavior changes are applied only to the event features associated with the route feature being edited.
The previous section shows the concept of time slicing a route based on the date values in the calibration point feature class and the centerline sequence table.
The Median_Type table represents the source table being used for event registration. From the input source table, one record for the event (EventID = 101238) is highlighted, but its temporal range spans more than one route feature (RouteID = 81251003).
After creating an LRS event, two event features will be created for the same route (RouteID) but with different date ranges. Each event feature will use the calibration and shape of the appropriate route feature, based on the temporal range, as the source to generate its shape as shown in the image below.
