Description of the Bug: Core Location intermittently reports inaccurate location updates, albeit with a high accuracy value. This problem occurs almost exclusively while travelling in metros underground affecting the ability to rely on the framework effectively. Steps to Reproduce: The user starts travelling on ground level at point A The user continues travelling and, after some time, is now underground at point B. A stationary beacon scanned at point B confirms this. Core Location is observed to deliver a location update with a high-accuracy value but with the coordinates around point A when the user is actually around point B. Expected Behaviour: Accurate locations should be delivered at all times. In other words, Core Location should not report location updates with high accuracy when its certainty is low.