Time slicing routes
Routes, in general, have their shape and calibration change over a period of time, and Esri Roads and Highways provides temporal support to represent and edit such routes by creating route features with proper time stamps (same Route ID but with different FromDate and ToDate values), thereby storing every version of the route. Time slicing the route happens because of changes in the shape of the route (realignment of roads) or 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. Let us consider an example to better understand this concept. The records in the calibration point feature class and centerline sequence shown below represent records of a route that has been realigned.
Let's take a 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 from January 1, 2012. Since the ToDate 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 happened on January 1, 2013, we have two more calibration changes to the M-values in the middle of the route, highlighted in turquoise, and the FromDate value is set to January 1, 2013. Since the ToDate value is set to null, these calibration points will always take part in the calibration of the route starting from January 1, 2013.
From the centerline sequence table, it is evident that the there are four centerlines that provide the shape for the route in two different time ranges, January 1, 2012 to January 1, 2013, and January 1, 2013 to forever. 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 from January 1, 2013, the route was realigned to follow the path depicted by centerline D.
In order to visualize the time slicing of route, the route features must be generated. Route features are initially created through the process of 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 event
Esri 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 internal event . During this process, if we have one event record in the source table whose FromDate and ToDate values span across multiple route features, then 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 also to ensure that event behavior changes get applied only to the event features associated with the route feature being edited. Let us take a look at an example to better understand this concept.
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 to register an internal event . From the input source table, we have highlighted one record for the event (EventID = 101238), but its temporal range spans more than one route feature (RouteID = 81251003).
After the process of LRS event creation, 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 depicted in the picture below.