[ios] Stop exaggerating heading accuracy indicator size

- 1.5× exaggeration has been removed.
- Maximum accuracy (smallest size) has been increased to 20°.

platform/ios/CHANGELOG.md

@@ -29,6 +29,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 
 * To customize the appearance of the user location annotation, subclass the newly added MGLUserLocationAnnotationView class and implement `-[MGLMapViewDelegate mapView:viewForAnnotation:]`. ([#5882](https://github.com/mapbox/mapbox-gl-native/pull/5882))
 * Fixed an issue causing the user dot’s accuracy ring to wobble while zooming in and out. ([#6019](https://github.com/mapbox/mapbox-gl-native/pull/6019))
+* Heading accuracy indicator sizing has been changed to appear more precise. ([#6120](https://github.com/mapbox/mapbox-gl-native/pull/6120))
 
 ### Annotations
 

platform/ios/src/MGLFaux3DUserLocationAnnotationView.m

@@ -502,10 +502,10 @@ const CGFloat MGLUserLocationAnnotationArrowSize = MGLUserLocationAnnotationPuck
 {
     CGFloat accuracy = self.userLocation.heading.headingAccuracy;
 
-    // size the mask using exagerated accuracy, but keep within a good display range
-    CGFloat clippingDegrees = 90 - (accuracy * 1.5);
-    clippingDegrees = fmin(clippingDegrees, 55);
-    clippingDegrees = fmax(clippingDegrees, 10);
+    // size the mask using accuracy, but keep within a good display range
+    CGFloat clippingDegrees = 90 - accuracy;
+    clippingDegrees = fmin(clippingDegrees, 70); // most accurate
+    clippingDegrees = fmax(clippingDegrees, 10); // least accurate
 
     CGRect ovalRect = CGRectMake(0, 0, MGLUserLocationAnnotationHaloSize, MGLUserLocationAnnotationHaloSize);
     UIBezierPath *ovalPath = UIBezierPath.bezierPath;