Real-time use cases - driver assistance and alerts
Route Matching can also be used for (almost) real-time use cases, where short traces from vehicles are matched and feedback during the journey is provided (driver alerts), or the journey is influenced (re-routing).
Matching a trace that contains the latest few hundred driven meters provides better match results than matching one single isolated coordinate.
Typically speed limits change alerts are returned to the driver, but also other map attribute changes can be reported.
Electronic Horizon - what's ahead of you
It is important for drivers to get upfront notifications of upcoming obstacles on the road ahead, beyond their current line of sight. This is not only important during bad light or snow covered road conditions, but also to know what happens behind the next corners, intersections or slopes.
Set the route match request parameter &routeMatch=4 or &routeMatch=5 to get in addition to the matched route the most probable path ahead of your matched route. While &routeMatch=5 extends on the end of the matched route, &routeMatch=4 just accepts a single coordinate with a heading as starting point of the horizon, which maight have a lower map matching quality.
The length of the horizon path can be limited to a certain driving distance or driving time using the &ehorizonLimits parameter. At intersections the most probable turn direction is computed preferring to stay on the same road, driving into the same direction or turning onto bigger, faster roads.
Due to the heuristic nature of the electronic horizon path its main use case is for just staying straight on a rural road or motorway, or staying straight on the big arterial road inside a city.
To create driver warnings, the same map attributes can be retrieved in the response for the horizon as for the matched route. Alternatively, the map attributes along the horizon can be retrieved using the Map Attributes API.