PTV Group - Logistics Forum

Hi there,

every once in a while we get asked for the usecase behind xMapMatch. Roughly spoken this is it (in the terminology of xMapMatch1):

Use xMapMatch to reconstruct a driven route based on a GPS track
The PTV xMapmatch Server tries to detect the most probable driven route based on the tracked GPS positions. The server uses map matching:

• Map matching is a technique to reference a GPS position on a digital map.
• Map matching dose not find the best routing solution. It detects the possible driven route in dependency of the frequency of received GPS signals.

Using the PTV xMapmatch Server, it is possible to determine on which street a car currently is most probably located. The geographic locations, which are used as input of the PTV xMapmatch Server, usually are provided by a GPS receiver or a combination of sensors which allow the determination of an approximated position. The accuracy of the positions detected by a device varies depending on several conditions. For example environmental influences or the method of position detection by the device itself. A GPS position for civil usage for example only allows an accuracy of 15 meter. Under sub-optimal conditions the detected position may differ from the actual position by 100 meter or more. Due to this reason PTV xMapmatch tries to find the possible driven route. It is not guaranteed that he find the exact route.

You can choose between two calculation modes:

• Global matching: Tries to reconstruct the possible driven route by using the already recorded GPS positions.
  GPS positions may not be accurate and in particular, the reference to the corresponding street segment is not known on the existing digital map. The PTV xMapmatch Server is building a history of previously determined positions on the street segments and is trying to predict the next street segment where a newly detected position might be occur in consideration of the previous detected locations. Doing this, inaccuracies of the incoming locations are relieved and more precise positions are identified to reference the actually used road segment.
• Local matching: Try to match one single GPS position on the digital map without considering the previous detected positions.

During the matching, driving restrictions are also included such as tunnels, one-way streets, pedestrian areas etc. Plausibility checks for the reconstruction of routes and the analysis of junction and turn-off situations ensure reliable results.

The PTV xMapmatch Server contains a standstill recognition and processes dense (second interval) and sparse signals (minute interval). It provides a road category (network class) for every matched segment and the permitted speed limit wherever available. In addition, the PTV xMapmatch Server provides a summary of the route. This contains the total distance and duration as well as a corresponding segment list and a polyline of the matched route.

Here are some more articles about the topic:

• Functional description: http://xserver.ptvgroup.com/en-uk/products/ptv-xserver/ptv-xmapmatch/
• There are some nice examples available in the online docu:
  http://xserver.ptvgroup.com/fileadmin/files/PTV-COMPONENTS/DeveloperZone/Documents/xServer_public/manual/Default.htm
• Our colleague Joost Claessen (Subsidary in Belenux) has developed a xMapMatch test client and he provides info about it here: http://xserver.ptvgroup.com/forum/viewt ... p?f=8&t=12

  

  Screenshot of Joost Claessens Testclient.

Best regards,
Bernd Welter

Let me add some more statements to this:

• If you compare xMapMatch1 with xMatch2 / PTV Developer's Map Matching API you'd probably see that the newer API's do not consider a timestamp for a given GPS cordinate. We discussed this internally during the design phase of the xMapMatch2 and decided against the usage of timestamps. But if you want to apply a specific TimeConsideration (e.g. because the toll on a driven route may depend on the time context during a segment usage) you can apply a regular time approach such as TimeCOnsideration (xRoute2) or "realistic or average" (PTV Developer).