Map Matching based on GraphHopper
Map matching is the process to match a sequence of real world coordinates into a digital map. Read more at Wikipedia. It can be used for tracking vehicles' GPS information, important for further digital analysis.
Currently this project is under heavy development but produces already good results for various use cases. Let us know if not and create an issue!
License
Apache License 2.0
Installation and Usage
Install Java and Maven. Then import the area you want to do map-matching on:
./map-matching.sh action=import datasource=./some-dir/osm-file.pbf
and then do these matches:
./map-matching.sh action=match gpx=./track-data/.*gpx
Possible flags to pass are the following:
gpxAccuracy=15 # default=15, type=integer, unit=meter
separatedSearchDistance=500 # default=500, type=integer, unit=meter
maxSearchMultiplier=50 # default=50, type=integer
forceRepair=flase # default=false, type=boolean
This will produce gpx results similar named as the input files.
Or use this Java snippet:
// import OpenStreetMap data
GraphHopper hopper = new GraphHopper();
hopper.setOSMFile("./map-data/leipzig_germany.osm.pbf");
hopper.setGraphHopperLocation("./target/mapmatchingtest");
CarFlagEncoder encoder = new CarFlagEncoder();
hopper.setEncodingManager(new EncodingManager(encoder));
hopper.setCHEnable(false);
hopper.importOrLoad();
// create MapMatching object, can and should be shared accross threads
Graph graph = hopper.getGraph();
LocationIndexMatch locationIndex = new LocationIndexMatch(graph, new RAMDirectory());
locationIndex.prepareIndex();
MapMatching mapMatching = new MapMatching(graph, locationIndex, encoder);
// do the actual matching, get the GPX entries from a file or via stream
List<GPXEntry> inputGPXEntries = new GPXFile("nice.gpx").read();
MatchResult mr = mapMatching.doWork(inputGPXEntries);
// return GraphHopper edges with all associated GPX entries
List<EdgeMatch> matches = mr.getEdgeMatches();
// now do something with the edges like storing the edgeIds or doing fetchWayGeometry etc
matches.get(0).edgeState
Later we will add a simple web service
UI to visually compare
There is a simple UI taken from makinacorpus/Leaflet.FileLayer where you can load your input and output gpx files to compare the results. Some GPX seem to fail when trying to load them.
Start e.g. via 'firefox simple-js-ui/index.html'
Note
Note that the edge and node IDs from GraphHopper will change for different PBF files, like when updating the OSM data.
About
The used algorithm is explained in this blog post.