RouteController drops batched location updates

[1ec5]

CLLocationManagerDelegate.locationManager(_:didUpdateLocations:) accepts an array of locations in chronological order, but we drop all but the latest in any given location update:

mapbox-navigation-ios/MapboxCoreNavigation/RouteController.swift

Lines 508 to 512 in 447dbf1

	@objc public func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
	guard let location = locations.last else {
	return
	}
	self.rawLocation = location

Sometimes location updates occur in a burst. If the user is traveling along a straight path, the older locations don’t matter. But if they’re traveling along a curve or turning at an intersection, the dropped locations could significantly affect camera movement.

/ref #939 mapbox/mapbox-gl-native#3610
/cc @mapbox/navigation-ios

[bsudekum]

Oooooo let's definitely not throw out data.

[ericrwolfe]

Is this a real issue? Are there concrete examples of issues with camera movements caused by missed location bursts?

From past experience, bursts of locations in didUpdateLocations generally only occur when 1) first starting a location manager and didUpdateLocations immediately returns a set of cached/stale locations and 2) when using allowDeferredLocationUpdates(untilTraveled:timeout:).

[1ec5]

You’re right, I can’t say that this is a real issue in practice (emphasis on could above). However, we’re starting to talk about inserting maneuver locations and other control points between actual location updates in order to stabilize the camera and puck, so it seems natural that we’d use these extra locations – if any – to better model the road.

[bsudekum]

Noting we now filter out unqualified locations, however we still look at the last item in this array of qualified locations.

[1ec5]

Since the migration to MapboxNavigationNative, RouteController sends all locations to the navigator.