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[Regression] Core Location underground positioning inaccurate on iOS 26.1 beta (23B5044i)
Summary While parallel testing Core Location on the new iOS 26.1 beta (23B5044i), I observed what I believe to be a regression of the issue described here: https://developer.apple.com/forums/thread/779192 Specifically, user positioning underground subway stations is noticeably inaccurate on the beta, whereas the same scenarios remain accurate on the unupgraded device below. I work with the MTA (New York City) and work with the OP of that thread. Happy to provide additional testing or details if helpful. Please let me know what else you need. Test Info Riding NYCT from Wall St to 34th St Penn Station on the 2 train carrying two iphones Recording: https://limewire.com/d/dpTWi#pDC3GRYIdE Expected: Consistent underground positioning comparable to prior releases. Actual: Degraded/inaccurate underground positioning on iOS 26.1 beta. Test Devices Left Screen: iPhone 15 Pro Max - iOS 26.1 beta (23B5044i) Right Screen: iPhone 11 - iOS 18.6.2 (22G100) Blue dots show location set by CoreLocation. Red dot on iphone 11 shows the actual location of both devices as I was able to manually place while travelling through a station. Placement through tunnels is not easy to verify and not usually indicated. Timestamps Comparison of when train was actually observed in a station vs when 26.1 and 18.6.2 CoreLocation updated to the station Fulton St 1:48 iOS 26.1 correctly updates (correctly) 2:16 iOS 18.6.2 updates (28sec late) Park Place 4:12 train arrives 4:15 iOS 18.6.2 updates to ~near Park Place 5:04 iOS 18.6.2 updates to Park Place (correctly) 6:07 iOS 26.1 update to ~near Park Place (over 2 mins late) Chambers St 6:02 train arrives / iOS 18.6.2 updates (correctly) 6:14 iOS 26.1 updates to ~near Chambers 6:18 iOS 26.1 update to Chambers (correctly) Franklin St 6:52 train arrives 6:55 iOS 18.6.2 updates (correctly) x:xx iOS 26.1 does not update Canal St: 7:16 train arrives 7:18 iOS 18.6.2 updates (correctly) x:xx iOS 26.1 does not update Houston St 7:54 train arrives 8:00 iOS 18.6.2 updates (correctly) x:xx iOS 26.1 does not update Christopher St 8:37 iOS 26.1 presumably between Houston St and Christopher St 8:40 train arrives / iOS 18.6.2 updates (correctly) x:xx iOS 26.1 does not update 14 St 9:22 train arrives 9:28 iOS 18.6.2 updates (correctly) 11:01 as train departs station iOS 26.1 updates (1.5 mins late)
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232
Oct ’25
Altitude for MKAnnotation
In MapKit, the MKAnnotation takes a CLLocationCoordinate2D. However, in 3D/Flyover mode, the user marker has a height position on the map. We are currently plotting points which have altitude, speed, heading, etc, and I have a method for creating a CLLocation with this information. What I'm trying to figure out is if there's a way to pass that information along to the MapKit rendering engine / annotations / AnnotationViews to recognize and show when in 3D mode. Is there any support for that currently?
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155
3w
Clarification needed regarding requirements for geofencing
In my app, I am using geofencing to perform an action when the user enter or leaves a specified location. The geofencing (CLMonitor) is active permanently, and should work across multiple app sessions or after the device is restarted. It should also work after the app was minimized or terminated. This worked perfectly with iOS 17 and prior, but with iOS 18, things changed. As soon as iOS 18 dropped, users were informing me that the app does no longer perform the entry/exit action reliably (without me making any changes to the app). Most of the times, events are missed entirely. Sometimes, after the user opens or resumes the app, duplicate events are delivered and/or events with the current time instead of the correct time of entry/exit. I am making sure that the app has the "Always" location permission before geofencing is enabled The gefocence radius is between 20 and 500m, but even with the max. radius specified, the geofencing is unreliable For the same user and geofence, the entry/exit event is delivered occasionally, but not always I am currently not using CLLocationManager.allowsBackgroundLocationUpdates (even though it's documented as "Apps that receive location updates when running in the background must include the UIBackgroundModes key (with the location value) in their app’s Info.plist file") because it wasn't necessary on iOS 17 and in my tests, using it didn't yield any improvements In my search for what could have caused this change, I found this WWDC video about location authorization: . It appears that with iOS 18, it is now required to have an active CLServiceSession to ensure that location updates are delivered to my app. Even though the video is long (and I've watched it multiple times), some things are still unclear. For example, the docs state: If your app actively receives and processes location updates and terminates, it should restart those APIs upon launch in order to continue receiving updates. Also, in the video it is stated that: ... So your job, ..., is to make sure that your process launch logic knows what features it has been tasked with pursuing, and re-takes session objects... But on the other hand it's also said that: you can only start holding one (a CLServiceSession) when your app is in the foreground and also ... CLMonitor.events won’t yield results when it is not in use, unless a session which was started in the foreground, .... To summarize my questions, for the geofencing to work as described above: when exactly do I need to create a CLServiceSession if the app is launched into the backgorund? Immediately in the applicationDidFinishLaunching method, even though the app is still in the background (applicationState is background)? Or later on, when the app is opened again by the user, e.g. in applicationDidBecomeActive (and applicationState is active)? do I need to specify the background mode capability as noted in the Handling location updates in the background article? do I need to create a CLBackgroundActivitySession as noted in the Handling location updates in the background article? does it matter, which of the four initializer methods I am using to create the CLServiceSession (with CLServiceSessionAuthorizationRequirementAlways)? does it matter if I specify NSLocationRequireExplicitServiceSession in the Info.plist or not when I already do ensure that the app has the "Always" location permission when the feature is being enabled Does a CLServiceSession last indefinitely and should it only be invalidated once the user disables the feature?
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1.2k
Nov ’25
Underground location (in subway) doesn't update properly
We (at the NYC MTA) are building a new subway/bus app and diving deep into location tracking on iOS. We’re encountering an issue with how Core Location functions in the subway, specifically regarding how long it takes to update a passenger’s location as they travel from station to station. As an example, please see this video: https://drive.google.com/file/d/1yaddkjyPEETvTEmClPAJ2wks8b-_whqB/view?usp=sharing The red dot is set manually (via a tap gesture) and represents the ground truth of where the phone actually is at that moment. The most critical moment to observe is when the train physically arrives at a station (i.e., when I can see the platform outside my window). At this moment, I update the red dot to the center of the station on the map. Similarly, I adjust the red dot when the train departs a station, placing it just outside the station in the direction of travel. The trip shown is from Rector St to 14 St. All times are in EST. I’d like to investigate this issue further since providing a seamless underground location experience is crucial for customers. As a point of comparison, Android phones exhibit near-perfect behavior, proving that this is technically feasible. We want to ensure the iOS experience is just as smooth.
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519
Feb ’25
I noticed that the Uber Driver app is able to get location in background without the permissions (How?)
The Uber Driver app is able to get background location and there’s no way to turn it off from settings. Unlike other apps where there’s always an option to turn off background location from settings. Is this a bug or special treatment for big companies? this matters to me because we’re in a similar business but our app has to request background permissions, explicitly. I am attaching both of the screenshots here for you to compare and see. Please note that I verified personally that Uber Driver app is able to get background location.
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2.1k
May ’25
kCLErrorLocationUnknown becoming a big issue
In the last few months we have seen a lot of the following errors in which it fails to retrieve location information. This seems to happen across multiple browsers and feels related to apple/mac OS more than the browsers. Error: "CoreLocationProvider: CoreLocation framework reported a kCLErrorLocationUnknown failure." Any suggestions or an ETA on when this can be fixed? I have seen other threads/posts on this but wanted a new one to highlight the issue is prevalent.
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948
Sep ’25
Incorrect position rendering of WGS84 coordinate in MKMapView: Discrepancy between Apple Maps (Hong Kong) and Amap (Mainland China)
I am encountering a coordinate rendering issue using MKMapView in my iOS app. I have a GPS coordinate in WGS84 format, which corresponds to a location in Hong Kong. When my device is physically located in Hong Kong, MKMapView displays the map with the "Apple Maps" label, and the WGS84 coordinate is rendered at the correct position. However, when the device is in Mainland China, MKMapView switches to display "Amap" (Gaode Maps) branding, and the same WGS84 coordinate is rendered at an incorrect position. I understand that Amap in Mainland China uses the GCJ-02 coordinate system, while Apple Maps typically uses WGS84. This discrepancy suggests a potential coordinate system mismatch, but I cannot definitively confirm which map type (and corresponding coordinate system) MKMapView is actually using in different regions. My key questions are: How can I programmatically or visually confirm the underlying map type (Apple Maps vs. Amap) and its coordinate system within MKMapView? Is there a way to simulate the Apple Maps environment for testing when physically located in Mainland China?
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242
Sep ’25
iOS26+, MKMapview crash
I have a UIViewController that uses MKMapview to display the motion history trajectory. Repeatedly entering and exiting UIViewController will cause a crash, and the crash stack is as follows: Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Subtype: KERN_INVALID_ADDRESS at 0x000000014bfc0fc8 Exception Codes: 0x0000000000000001, 0x000000014bfc0fc8 VM Region Info: 0x14bfc0fc8 is not in any region. Bytes after previous region: 217033 Bytes before following region: 61496 REGION TYPE START - END [ VSIZE] PRT/MAX SHRMOD REGION DETAIL VM_ALLOCATE 14bf88000-14bf8c000 [ 16K] rw-/rwx SM=PRV ---> GAP OF 0x44000 BYTES VM_ALLOCATE 14bfd0000-14bfd4000 [ 16K] rw-/rwx SM=PRV Termination Reason: SIGNAL 11 Segmentation fault: 11 Terminating Process: exc handler [1881] Triggered by Thread: 8 Thread 8 name: Dispatch queue: com.apple.root.background-qos Thread 8 Crashed: 0 CoreFoundation 0x19e36ac40 CFRelease + 44 1 VectorKit 0x1ce16af6c md::TileGroupNotificationManager::~TileGroupNotificationManager() + 132 2 VectorKit 0x1cd6f7178 <deduplicated_symbol> + 76 3 VectorKit 0x1cdba8d74 -[VKSharedResources .cxx_destruct] + 32 4 libobjc.A.dylib 0x19b3321f8 object_cxxDestructFromClass(objc_object*, objc_class*) + 116 5 libobjc.A.dylib 0x19b32df20 objc_destructInstance_nonnull_realized(objc_object*) + 76 6 libobjc.A.dylib 0x19b32d4a4 _objc_rootDealloc + 72 7 VectorKit 0x1cdba93fc -[VKSharedResources dealloc] + 476 8 VectorKit 0x1cdafa3fc -[VKSharedResourcesManager _removeResourceUser] + 68 9 VectorKit 0x1cdafa380 +[VKSharedResourcesManager removeResourceUser] + 44 10 VectorKit 0x1cdafa2fc __37-[VKIconManager _internalIconManager]_block_invoke + 168 11 libdispatch.dylib 0x1d645b7ec _dispatch_client_callout + 16 12 libdispatch.dylib 0x1d6446664 _dispatch_continuation_pop + 596 13 libdispatch.dylib 0x1d6459528 _dispatch_source_latch_and_call + 396 14 libdispatch.dylib 0x1d64581fc _dispatch_source_invoke + 844 15 libdispatch.dylib 0x1d6453f48 _dispatch_root_queue_drain + 364 16 libdispatch.dylib 0x1d64546fc _dispatch_worker_thread2 + 180 17 libsystem_pthread.dylib 0x1f9b7e37c _pthread_wqthread + 232 18 libsystem_pthread.dylib 0x1f9b7d8c0 start_wqthread + 8 I have checked the code and did not find any issues. I have also tested on iOS 15, 16, and 18 without any issues. Could this be an error in the iOS 26 system? Have you ever met any friends? I hope to receive an answer. Thank you.
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291
Nov ’25
Background Modes - App Identifiers
Hey All, Seem to be in a loop and unable to proceed. New app specific for iOS being built on xCode. Project is configured only to deploy and use iOS, not macOS or anything else. Trying to create a new App iD always see it default to all platforms which means "Background Modes" is not visible or available. Automatic signing etc in xcode can't seem to get around this and just continues to flag I'm missing the entitlement for locations.background. Not sure what I am missing as I cannot manually configure the ID for iOS only and xcode is also generating new ID's with the same platform structure and constraints. Any thoughts or insights here please?
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155
Apr ’25
Dynamic Location Tracking using CLServiceSession and CLBackgroundActivitySession
Hello, I'm currently implementing code to track routes and determine if users have arrived at their destination using CLServiceSession, CLBackgroundActivitySession, and CLLocationUpdate.liveUpdates. I want to obtain location data across all app states: foreground, background, and terminated. I have two questions: Background Location Indicator Issue: I'm using CLBackgroundActivitySession to get location updates in the background. Normally, the background location indicator (blue bar) doesn't appear at the top left of the screen for my app. However, when another app (e.g., LiveUpdatesSample) activates CLBackgroundActivitySession, my app's background location indicator suddenly becomes visible. Can you explain why this happens? or Can I Control showsBackgroundLocationIndicator in CLBackgroundActivitySession Session Management: Is there a way to terminate all currently active CLBackgroundActivitySessions? I understand that when CLBackgroundActivitySession is activated and the app is terminated and then relaunched, a new CLBackgroundActivitySession needs to be created. In this case, are the previously created and running CLBackgroundActivitySessions automatically released when the app is relaunched?
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209
Jul ’25
MKReverseGeocodingRequest and CNPostalAddress from MKMapItem
My app is currently using CLGeocoder to get a CLPlacemark, then using placemark.postalAddress with CNPostalAddressFormatter to get an attributed string for the full address, I then enumerate its attributes to pull out specific elements like just the street or state or zip etc. This is deprecated in iOS 26 with MKReverseGeocodingRequest being the intended replacement. This API returns an MKMapItem which doesn’t provide a CNPostalAddress - you can get a full address as a String but not structured address data that I’m seeing. Am I missing some way to get the postal address? Or is it a non-goal to provide that anymore? Thanks!
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3w
App Clips Advanced Experiences not showing up in Apple Maps and Siri Suggestions
Hello everyone, I’m experiencing an issue with App Clips Advanced Experiences and Apple Maps/Siri Suggestions. We have already contacted Apple Support before, but they are investigating the cause of this issue and it has not been resolved til date. The App Clip is bundled with the main app and has been already available on the App Store for several months. The business running the app has several physical shops and wants to offer the App Clip to show up in Apple Maps and Siri Suggestions at each location. The App Clip is correctly exposed in the AASA file, and it's also validated correctly by the AASA APIs available at https://app-site-association.cdn-apple.com/a/v1. { "applinks": { "apps": [], "details": [ { "appID": "TEAMID.bundleid", "paths": [] } ] }, "appclips": { "apps": [ "TEAMID.bundleid.Clip" ] } } (with TEAMID and bundleid being the team and bundle identifiers of the app) The App Clip is displayed correctly when loading the website and when scanning a QR code or App Clip code, but doesn't appear in the Maps app or in Siri suggestions. We have set up the App Clip Advanced Experiences on the App Store Connect page of the app, and each URL has been linked to a physical shop. All URLs are in the "Received" state, so they should appear correctly on Maps. Unfortunately, I don't see any "Order" button in Apple Maps at any location card. We tried with both iOS 17 and 16. According to feedbacks from people in the shops, they don't see the app suggested in the Siri Suggestions. I have just submitted a Custom Action Link on Apple Business Connect for one of the shops, but without success: the App Clip doesn't appear. Any idea why is this happening?
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986
Mar ’25
Unable to use altitude for our use case (NYC MTA)
We’re building a new subway/bus app at the MTA. Our system includes roughly 300 underground stations, around 150 elevated stations (i.e., above street level), and about 5 at-grade stations (i.e., at street level). We serve roughly 5 million riders a day. We’re diving deep into Core Location on iOS and have found that the altitude values returned from two fields we’re testing aren’t accurate enough for our use case: CLLocation.altitude CMAbsoluteAltitudeData.altitude We need to reliably distinguish whether a user is: At street level On an elevated platform (see attached picture) On any platform in an underground station — most have a single platform level, but some, like 59 St (see attached), have multiple platforms at different elevations. These levels typically differ by at least 15 feet, which should in theory be well within the precision range of a properly calibrated barometric pressure sensor. However, the absolute altitude values we’re seeing from these APIs are often inaccurate and inconsistent — not only compared to ground truth, but also across devices. For example, holding two phones side-by-side frequently yields altitude readings that differ by more than 15 feet. That level of variation makes the data unreliable for our needs. Please see the below photos for more context. URLs.md
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230
Apr ’25