[ios] z14 initially in user tracking mode

When entering user tracking mode from a low zoom level, zoom in to z14 regardless of the location’s horizontal accuracy.

CHANGELOG.md

@@ -49,6 +49,7 @@ Known issues:
 - MGLMapView properties like `centerCoordinate` and `camera` now offset the center to account for any translucent top or bottom bar. As a result, when user tracking is enabled and the map view is an immediate child of a view controller, the user dot is centered in the unobscured portion of the map view. To override this offset, modify the `contentInset` property; you may also need to set the containing view controller’s `automaticallyAdjustsScrollViewInsets` property to `NO`. ([#3583](https://github.com/mapbox/mapbox-gl-native/pull/3583))
 - In user tracking mode, the user dot stays in a fixed position within MGLMapView while the map pans smoothly. A new property, `userLocationVerticalAlignment`, determines the user dot’s fixed position. ([#3589](https://github.com/mapbox/mapbox-gl-native/pull/3589))
 - Zooming and rotation gestures no longer disable user tracking mode. ([#3589](https://github.com/mapbox/mapbox-gl-native/pull/3589))
+- User tracking mode starts out at a lower zoom level by default. ([#3589](https://github.com/mapbox/mapbox-gl-native/pull/3589))
 - Fixed an issue with small map views not properly fitting annotations within bounds. (#[3407](https://github.com/mapbox/mapbox-gl-native/pull/3407))
 - When the user rotates the map to within 7° of true north, the map view now snaps to true north. ([#3403](https://github.com/mapbox/mapbox-gl-native/pull/3403))
 - The map view’s background can now be transparent or translucent, as long as the style’s background layer is transparent or translucent and `MGLMapView.opaque` is set to `NO`. ([#3096](https://github.com/mapbox/mapbox-gl-native/pull/3096))

platform/ios/src/MGLMapView.mm

@@ -68,6 +68,13 @@ const NSTimeInterval MGLUserLocationAnimationDuration = 1.0;
 
 const CGSize MGLAnnotationUpdateViewportOutset = {150, 150};
 const CGFloat MGLMinimumZoom = 3;
+
+/// Minimum initial zoom level when entering user tracking mode.
+const double MGLMinimumZoomLevelForUserTracking = 10.5;
+
+/// Initial zoom level when entering user tracking mode from a low zoom level.
+const double MGLDefaultZoomLevelForUserTracking = 14.0;
+
 const NSUInteger MGLTargetFrameInterval = 1;  //Target FPS will be 60 divided by this value
 
 /// Tolerance for snapping to true north, measured in degrees in either direction.
@@ -3095,7 +3102,7 @@ std::chrono::steady_clock::duration MGLDurationInSeconds(float duration)
 
         if (std::abs(currentPoint.x - correctPoint.x) > 1.0 || std::abs(currentPoint.y - correctPoint.y) > 1.0)
         {
-            if (round(self.zoomLevel) >= 10)
+            if (self.zoomLevel >= MGLMinimumZoomLevelForUserTracking)
             {
                 // at sufficient detail, just re-center the map; don't zoom
                 //
@@ -3140,7 +3147,9 @@ std::chrono::steady_clock::duration MGLDurationInSeconds(float duration)
                 MGLMapCamera *camera = self.camera;
                 camera.centerCoordinate = self.userLocation.location.coordinate;
                 camera.heading = course;
-                camera.altitude = newLocation.horizontalAccuracy;
+                camera.altitude = MGLAltitudeForZoomLevel(MGLDefaultZoomLevelForUserTracking, camera.pitch,
+                                                          camera.centerCoordinate.latitude,
+                                                          self.frame.size);
                 
                 __weak MGLMapView *weakSelf = self;
                 [self _flyToCamera:camera withDuration:animated ? -1 : 0 peakAltitude:-1 completionHandler:^{