How to plot the map matching result using edgeID

Open Source Routing Engine Map Matching
1

Hi. I am new to graphhopper and java. I am trying to plot the paths and snapped points by using the returned edgeID and snapped coordinates. Here are the codes I run the map matching function in MapMatching class.

package com.graphhopper.matching;
import com.graphhopper.GraphHopper;
import com.graphhopper.config.LMProfile;
import com.graphhopper.config.Profile;
import com.graphhopper.util.Helper;
import com.graphhopper.util.PMap;
import com.graphhopper.util.shapes.GHPoint;

import java.io.*;
import java.util.*;
import java.util.ArrayList;
import java.util.List;


public class testMapMatching2 {

    // declare attributes
    private static final String GH_LOCATION = "../target/mapmatchingtest-ch";
    private static GraphHopper graphHopper;



    public static void main(String args[]) throws Exception {


        // import gps data from the csv file
        String line = "";
        String splitBy = ",";

        List<Observation> coordinates = new ArrayList<>();

        try
        {
            //parsing a CSV file into BufferedReader class constructor
            BufferedReader br = new BufferedReader(new FileReader(
                    "C:\\output_gps\\allgps.csv"));

            // create the index
            ListIterator<Observation> iter = coordinates.listIterator();

            // consume the first line and ignore
            br.readLine();

            // read the data line by line
            while ((line = br.readLine()) != null)   //returns a Boolean value
            {
                String[] coordinate = line.split(splitBy);    // use comma as separator
                coordinates.add(iter.nextIndex(),new Observation(new GHPoint( Double.valueOf(coordinate[1]),
                       Double.valueOf(coordinate[2])))); // add each line into the arraylist
            }
//            System.out.println(coordinates); // check the output
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }

      // set up graphHopper
        Helper.removeDir(new File(GH_LOCATION));
        graphHopper = new GraphHopper();
        graphHopper.setOSMFile("C:\\map-matching\\files\\singapore-latest.osm.pbf");
        graphHopper.setGraphHopperLocation(GH_LOCATION);
        graphHopper.setProfiles(new Profile("my_profile").setVehicle("bike").setWeighting("fastest"));
        graphHopper.getLMPreparationHandler().setLMProfiles(new LMProfile("my_profile"));
        graphHopper.importOrLoad();


        // set up hints - set the profile
        PMap hintsObj = new PMap();
        PMap hints = hintsObj.putObject("profile", "my_profile");

        // conduct map matching - call match()
        MapMatching2 obj = new MapMatching2(graphHopper, hints);
        MatchResult2 mr = obj.match(coordinates);

        // store the output into String
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        PrintStream ps = new PrintStream(baos);
        PrintStream old = System.out;
        System.setOut(ps);

        System.out.println("edge_ID," + "snap1," + "snap2," + "snap3," + "snap4," + "\n" + mr);

        System.out.flush();
        System.setOut(old);

        String baosString = baos.toString();
        System.out.println(baosString);

        // store String into a text file
        try{
            FileWriter fw=new FileWriter("C:\\distanceCalculation\\output\\distanceAMK.txt");
            fw.write(baosString);
            fw.close();
        }catch(Exception e){System.out.println(e);}
        System.out.println("Success...");


}


}

For the result, I can get the edgeID and the coordinates of snapped points. Is there a way to plot the paths by using the edgeID? Can the edgeID link to OSM wayID? Thank you in advance.

2

You can get the coordinates (PointList) of each edge like this:

List<EdgeMatch> edgeMatches = mr.getEdgeMatches();
PointList pointList = edgeMatches.get(0).fetchWayGeometry(FetchMode.ALL);

The OSM way ID is not included by default. But searching the forum you should be able to figure out how to do this.

3

Hi, I´m also trying to plot paths and snapped points.

@Ms_CHEN_Xinyu What is the MapMatching2 class you are using? Is it different from the standard MapMatching? The MapMatching class has a obj.doWork method, but not the obj.match(coordinates) that you are using. Where do you get it from?

@easbar The same happens with fetchWayGeometry. I don’t find it in EdgeMatch.

Any help on what am I doing wrong?

How can I get a one to one list of snapped points from a list of observations?

4

You can do edgeMatches.get(0).getEdgeState().fetchWayGeometry(FetchMode.ALL);. I think this was a typo in my previous post (missing the getEdgeState() call).

5

Just in case it is useful for someone, I solved my issue with the following code:

Profile profile=new Profile("car");
profile.getHints().putObject("profile", "car");
MapHandler.getMapHandler().getHopper().setProfiles(profile);

mapMatching=new MapMatching(MapHandler.getMapHandler().getHopper(),profile.getHints());

matchResult=mapMatching.doWork(observations);
        
Path path = matchResult.getMergedPath();
PointList pointList= path.calcPoints();

I’m not using the previously mentioned MapMatching.match , but it can be found in:
https://github.com/graphhopper/graphhopper/blob/master/map-matching/src/main/java/com/graphhopper/matching/MapMatching.java