Map matching: very difficult to get a route with coordinates

[tezqa]

Hello,

I have a backend where I can trace a route with OSRM. I receive in my iOS app a list of coordinates, from the first to the last location, with all intermediates locations between them.

I calculate the route like this:

func calculateRoute(locations: [CLLocationCoordinate2D],
                      completion: @escaping (Route?, Error?) -> ()) {
    let matchOptions = NavigationMatchOptions(coordinates: locations, profileIdentifier: .automobile)
    
    matchOptions.includesSteps = true
    matchOptions.waypointIndices = IndexSet([0, locations.count - 1])
    matchOptions.distanceMeasurementSystem = .metric

    Directions.shared.calculateRoutes(matching: matchOptions) { (waypoint: [Waypoint]?, routes: [Route]?, error: Error?) in
      completion(routes?.first, error)
    }
  }

But nearly every time, I don't receive any route matching the coordinates:

routes = nil

Error Domain=MBDirectionsErrorDomain Code=-1 "No matching found" UserInfo={NSLocalizedFailureReason=No matching found}

I succeeded one time to receive a valid route (every location perfectly placed on a main street or a road). And when everything seems ok, it often fails.

Is there something i'm doing wrong? Any chances to increase a margin or something else to match a location if it's not perfectly located?

When I calculate routes with waypoints, all works fine but since all waypoints are considered as a place to visit, It's not a workaround for me.

[tezqa]

Here is a list of coordinates with an error for the route calculation:

1. 48.846413943401 2.3445725440979
2. 48.86271029257 2.313244342804
3. 48.8592281 2.2671622
4. 48.859844609102 2.1876311302185
5. 48.8733692 2.1689624
6. 48.875098 2.1686524
7. 48.816726632755 2.0635628700256
8. 48.688778988723 2.0142531394958
9. 48.6463299 1.8187715
10. 48.4048011 2.6885733

[tezqa]

I'm looking for a workaround and maybe the issue is that the option radiuses is missing in the request sent by Directions.shared.calculateRoutes.

This option is available in the Android SDK. https://www.mapbox.com/android-docs/api/mapbox-java/libjava-services/3.0.0/com/mapbox/api/matching/v5/MapboxMapMatching.Builder.html

Is it a omission?

[tezqa]

Update:

I have created a variant of NavigationMatchOptions to set the maximum (49 meters) for each location's coordinateAccuracy, used to set radiuses in the request (the existing NavigationMatchOptions set coordinateAccuracy to -1 to ignore radiuses in the request, I don't know why):

open class BLNavigationMatchOptions: MatchOptions {
  
  /**
   Initializes a navigation route options object for routes between the given waypoints and an optional profile identifier optimized for navigation.
   
   - SeeAlso:
   [MatchOptions](https://www.mapbox.com/mapbox-navigation-ios/directions/0.19.0/Classes/MatchOptions.html)
   */
  @objc public required init(waypoints: [Waypoint], profileIdentifier: MBDirectionsProfileIdentifier? = .automobileAvoidingTraffic) {
    super.init(waypoints: waypoints.map {
      $0.coordinateAccuracy = 49
      return $0
    }, profileIdentifier: profileIdentifier)
    includesSteps = true
    routeShapeResolution = .full
    attributeOptions = [.congestionLevel, .expectedTravelTime]
    includesSpokenInstructions = true
    locale = Locale.nationalizedCurrent
    distanceMeasurementSystem = Locale.current.usesMetricSystem ? .metric : .imperial
    includesVisualInstructions = true
  }
}

And I use it like this:

    var waypoints: [Waypoint] = []
    for loc in locations {
      let wp = Waypoint(coordinate: loc)
      waypoints.append(wp)
    }
    let matchOptions = BLNavigationMatchOptions(waypoints: waypoints, profileIdentifier: .automobile)
 
    matchOptions.includesSteps = true
    matchOptions.waypointIndices = IndexSet([0, 1, locations.count - 1])
    matchOptions.distanceMeasurementSystem = .metric
    
    Directions.shared.calculateRoutes(matching: matchOptions) { (waypoint: [Waypoint]?, routes: [Route]?, error: Error?) in
      completion(routes?.first, error)
    }

But it still doesn't work!

The response returns route=nil and this error:

Error Domain=MBDirectionsErrorDomain Code=-1 "No matching found" UserInfo={NSLocalizedFailureReason=No matching found}

Here are my coordinates:

0. 48.56918 2.32506
1. 48.404897375554 2.6886409521103
2. 48.402379742784 2.6968270540237

Why is it impossible to get a route matching?

[1ec5]

the existing NavigationMatchOptions set coordinateAccuracy to -1 to ignore radiuses in the request, I don't know why

I think the expectation is that NavigationMatchOptions’ coordinates would come directly from Core Location, which sets CLLocation.coordinateAccuracy automatically but somewhat unreliably. But I don’t think we meant to clear out an accuracy that’s set manually. −1 is normally a placeholder value indicating that the option is unset. (For example, this library needs to bridge to Objective-C, which means we can’t make any CLLocationDistance-typed property optional.)

So the coordinateAccuracy should be unset further up the call chain, in NavigationMatchOptions(locations:profileIdentifier:) or Waypoint(location:), or preferably in whatever calls NavigationMatchOptions(locations:profileIdentifier:).

[1ec5]

So the coordinateAccuracy should be unset further up the call chain, in NavigationMatchOptions(locations:profileIdentifier:) or Waypoint(location:), or preferably in whatever calls NavigationMatchOptions(locations:profileIdentifier:).

mapbox/mapbox-navigation-ios#1907

[1ec5]

There’s a simpler workaround in https://github.com/mapbox/mapbox-navigation-ios/issues/1907#issuecomment-448808887, by the way.

[tezqa]

@1ec5 I answered you on this issue. The workaround is here: https://github.com/mapbox/mapbox-navigation-ios/issues/1907#issuecomment-460666967