andrewharvey/probematch

A small module for matching probes to road networks

@mapbox/probematch

Match a single GPS measurements (probe) or line of sequential GPS measurements (trace) to a road network.

probematch creates an flatbush index of a road network to allow you to quickly match probes or traces to the roads using configurable distance and bearing filters.

terms

• probe - a single GPS measurement, represented by a Feature<Point>
• trace - a collection of sequential GPS measurements, represented by a Feature<LineString>
• road - a Feature<LineString> representing a road, which we may attempt to match probes and traces to
• roads, network, road network - a FeatureCollection of roads
• segment - a single edge of a road. For road A -> B -> C, there are two segments: A -> B and B -> C. Segments always have only 2 points.

install

npm install @mapbox/probematch

configuration

var probematch = require('@mapbox/probematch');

var roads = {
  'type': 'FeatureCollection',
  'features': [
    // Linestring features representing the road network
  ]
};

var matcher = probematch(roads, {
  compareBearing: true,
  maxBearingRange: 5,
  bidirectionalBearing: false,
  maxProbeDistance: 0.01
});

key	type	default	description
compareBearing	boolean	true	Should bearing of probes be used to evaluate match quality? If true, the bearing of the probe is compared to the bearing of each possible matching road segment. This ensures probes don't match cross-streets that obviously aren't the same as the probe's direction of travel
maxBearingRange	number	5	Maximum amount in degrees that a probe's bearing may differ from a road segment's when using compareBearing
bidirectionalBearing	boolean	false	Should bearing matches allow for probes to be moving in the opposite direction of a road segment's bearing? This should be true if the road network includes 2-way roads.
maxProbeDistance	number	0.01	Maximum distance in kilometers that a probe may be from a road segment in order to consider it a possible match. Prevents matching probes to segments that are too far away from them.

usage

match

var probematch = require('@mapbox/probematch');

var roads = /* FeatureCollection of road geometries */;
var matcher = probematch(roads, {/* configuration */});

var probe = {
  type: 'Feature',
  geometry: {
    type: 'Point',
    coordinates: [0, 0]
  }
};

var probeBearing  = 57; // probe's direction of travel in degrees

var results = matcher(probe, probeBearing);

The result of matching a single proble is an array of possible matches to the road network. Results are ordered by the probe's distance from the candidate road.

Each possible match represents a road that is likely to have matched the probe.

key	type	description
road	Feature<LineString>	The geometry of a road that may have been matched
index	Number	The start index of the segment closest to the probe may have matched (in the road's coordinates)
distance	number	Distance (in kilometers) between the probe and the road
bearing	number	The bearing of the road at the location that matched

matchTrace

var probematch = require('@mapbox/probematch');

var roads = /* FeatureCollection of road geometries */;
var matcher = probematch(roads, {/* configuration */});

var results = matcher.matchTrace(line);

matchTrace returns an array of match results. The order of results is the same as the order of the coordinates in the input trace. This means that the zeroeth element in the matchTrace result is an array of possible matches for the zeroeth coordinate, and so on.