Defining GPS Accuracy for MapMatching via CLI

Weltstaat · July 1, 2021, 2:09pm

Hi,

is it possible to define the GPS accuracy when using Map Matching from the Command Line? I can only find the parameter in the Map Matching UI at http://localhost:8989/maps/map-matching/

Thanks for your help!

easbar · July 1, 2021, 3:20pm

Yes, there is a --gps_accuracy option:

github.com

graphhopper/graphhopper/blob/76d6526f62264532e7e72dca989f6b41c44ecf33/web/src/main/java/com/graphhopper/http/cli/MatchCommand.java#L53-L79

    
      
          public void configure(Subparser subparser) {
              subparser.addArgument("gpx")
                      .type(File.class)
                      .required(true)
                      .nargs("+")
                      .help("GPX file");
              subparser.addArgument("--file")
                      .required(true)
                      .help("application configuration file");
              subparser.addArgument("--profile")
                      .type(String.class)
                      .required(true)
                      .help("profile to use for map-matching (must be configured in configuration file)");
              subparser.addArgument("--instructions")
                      .type(String.class)
                      .required(false)
                      .setDefault("")
                      .help("Locale for instructions");
              subparser.addArgument("--gps_accuracy")
                      .type(Integer.class)

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Weltstaat · July 2, 2021, 6:26am

Great, thank you!

A follow-up question: Is it already possible to define custom profiles within Map Matching (e.g. to include roads with access=no)?

Thanks

easbar · July 2, 2021, 6:55am

No this is not implemented yet. There is this issue though: Support custom_model for /spt, /isochrone and /match · Issue #2261 · graphhopper/graphhopper · GitHub

Without using landmarks this is also relatively easy to do if you know a bit of java. You can just create the weighting in MapMatching.java, something like this:

  CustomWeighting weighting = CustomModelParser.createWeighting(encoder, turnCostProvider, 
new CustomModel().addToSpeed(Statement.If("road_class == MOTORWAY", Statement.Op.MULTIPLY, 0.8)));

But access=no is actually a bit more complicated because it is not included in custom models yet. So you probably need to adjust OSMRoadAccessParser and run the import again.

Weltstaat · July 2, 2021, 8:06am

Thank you

isha-17 · July 12, 2021, 7:31am

Is it possible to do the same for the noise parameter, ‘measurementErrorSigma’?

I have tried simply changing the value in the MapMatching.java file and then performing the build, but this does not make a difference to the results - is that because I call the map matching through CLI?

easbar · July 12, 2021, 12:59pm

The measurementErrorSigma parameter can be set via the gps_accuracy option via CLI or which parameter do you mean?