TMC

Technical documentation

http://read.pudn.com/downloads53/doc/comm/185140/14819_1.pdf

How to gain TMC Data

The TMC Data is hidden inside the RDS Signal. It contains a location and a event. The event could be something like “traffic jam in the following 5km”

Sample Devices

Problems with TMC

In the order of the biggest to the lowest problem (one means biggest problem)

  1. TMC location code table is not good to match with the maps

    1. coverage of TMC is zero in all countries except Germany with 2%

    2. maptool currently discards all TMC information

    3. [STRIKEOUT:It could not (really) automatically merged] The traffic module can match the location of an event from the map, based only on coordinates and road attributes

  2. [STRIKEOUT:Navit currently has no traffic providers] Generic traffic functionality is available as a module, a functional traffic provider is available for Android

  3. Every location code table and event code table must be obtained separately

Idea how to get TMC Data inside Navit

Extend the NMEA Data to have a custom tag called “PTMCA” witch must defined later. PTMCA stands for “Proprietary TMC announcement”. The P in front is because its common and stands for proprietary. The TMC is because its TMC data. And the A is the type, in this case “announcement”.

Something similar is already commercially available from RoyalTek. Some information about the protocol is available here:

Other Ideas

Traffic is currently being implemented, see Traffic in Navit. The traffic branch works with a universal format called TraFF. TMC is received with an external app, converted to TraFF and fed into the plugin (Android only at the moment). The external app handles all location decoding; the TraFF data contains coordinates along with road numbers and road names, where available.

This approach is not limited to TMC: the external app could, in theory, pull traffic events from any source, convert them into TraFF and feed them into Navit.

Matching is currently done by coordinates, thus lack of TMC coverage in OSM is not a deal-breaker. However, TMC codes could be used to improve the quality of location matching—this would require some extensions to the code.

See also

Sources