Event Types
Events are categorized into point events and line events, stored in point event tables and line event tables respectively.
- Point events and point event tables
A point event occurs at an exact position along a route. Examples include traffic accidents on highways, speed cameras, bus stops, or valves on pipelines. In a point event table, each point event corresponds to a route ID (route identifier field) and uses a measure field to store its position.
Figure: Schematic diagram of point events - Line events and line event tables
A line event occurs along a route segment. Examples include road pavement materials, traffic congestion status, pipeline diameters, or collapsed road sections. As shown below, each line event in a line event table must contain a route ID (route identifier field), with from-measure and to-measure fields storing its positional information.
Figure: Schematic diagram of line events From-measure field: Stores the measure value of the line event's starting point on the route.
To-measure field: Stores the measure value of the line event's ending point on the route.
Generate Event Table
Generating an event table is the process of creating attribute tables containing point or line events. Event tables can be manually populated or generated by combining existing point/line datasets with route datasets.
This process is divided into generating point event tables and line event tables based on event types.
- Generating point event tables
Creates point event tables from point data and route data. A buffer zone (search radius) is generated around the route. Points within this zone are used to generate events, with each point corresponding to an event. Points outside the zone are excluded. The generated point data will include two new property fields storing route ID and M value.
Figure: Schematic diagram of point event table generation - Generating line event tables
Similar to point event generation, lines fully within the search radius will generate line events. Property fields include route ID, from-measure, and to-measure values. Lines partially or completely outside the radius are excluded. In the following diagram, line L2 exceeds the search radius and thus no event is generated.
Figure: Schematic diagram of line event table generation