Core Location Diagnostics

Symptom-based troubleshooting for Core Location issues.

When to Use

• Location updates never arrive
• Background location stops working
• Authorization always denied
• Location accuracy unexpectedly poor
• Geofence events not triggering
• Location icon won't go away

Related Skills

• axiom-core-location — Implementation patterns, decision trees
• axiom-core-location-ref — API reference, code examples
• axiom-energy-diag — Battery drain from location
• axiom-mapkit-diag — For map-specific location display issues (Symptom 7)

Symptom 1: Location Updates Never Arrive

Quick Checks

// 1. Check authorization
let status = CLLocationManager().authorizationStatus
print("Authorization: \(status.rawValue)")
// 0=notDetermined, 1=restricted, 2=denied, 3=authorizedAlways, 4=authorizedWhenInUse

// 2. Check if location services enabled system-wide
print("Services enabled: \(CLLocationManager.locationServicesEnabled())")

// 3. Check accuracy authorization
let accuracy = CLLocationManager().accuracyAuthorization
print("Accuracy: \(accuracy == .fullAccuracy ? "full" : "reduced")")

Decision Tree

Q1: What does authorizationStatus return?
├─ .notDetermined → Authorization never requested
│   Fix: Add CLServiceSession(authorization: .whenInUse) or requestWhenInUseAuthorization()
│
├─ .denied → User denied access
│   Fix: Show UI explaining why location needed, link to Settings
│
├─ .restricted → Parental controls block access
│   Fix: Inform user, offer manual location input
│
└─ .authorizedWhenInUse / .authorizedAlways → Check next

Q2: Is locationServicesEnabled() returning true?
├─ NO → Location services disabled system-wide
│   Fix: Show UI prompting user to enable in Settings → Privacy → Location Services
│
└─ YES → Check next

Q3: Are you iterating the AsyncSequence?
├─ NO → Updates only arrive when you await
│   Fix: Task { for try await update in CLLocationUpdate.liveUpdates() { ... } }
│
└─ YES → Check next

Q4: Is the Task cancelled or broken?
├─ YES → Task cancelled before updates arrived
│   Fix: Ensure Task lives long enough (store in property, not local)
│
└─ NO → Check next

Q5: Is location available? (iOS 17+)
├─ Check update.locationUnavailable
│   If true: Device cannot determine location (indoors, airplane mode, no GPS)
│   Fix: Wait or inform user to move to better location
│
└─ Check update.authorizationDenied / update.authorizationDeniedGlobally
    If true: Handle denial gracefully

Info.plist Checklist

<!-- Required for any location access -->
<key>NSLocationWhenInUseUsageDescription</key>
<string>Your clear explanation here</string>

<!-- Required for Always authorization -->
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>Your clear explanation here</string>

Missing these keys = silent failure with no prompt.

Symptom 2: Background Location Not Working

Quick Checks

1. Background mode capability: Xcode → Signing & Capabilities → Background Modes → Location updates
2. Info.plist: Should have UIBackgroundModes with location value
3. CLBackgroundActivitySession: Must be created AND held

Decision Tree

Q1: Is "Location updates" checked in Background Modes?
├─ NO → Background location silently disabled
│   Fix: Xcode → Signing & Capabilities → Background Modes → Location updates
│
└─ YES → Check next

Q2: Are you holding CLBackgroundActivitySession?
├─ NO / Using local variable → Session deallocates, background stops
│   Fix: Store in property: var backgroundSession: CLBackgroundActivitySession?
│
└─ YES → Check next

Q3: Was session started from foreground?
├─ NO → Cannot start new session from background
│   Fix: Create CLBackgroundActivitySession while app in foreground
│
└─ YES → Check next

Q4: Is app being terminated and not recovering?
├─ YES → Not recreating session on relaunch
│   Fix: In didFinishLaunchingWithOptions:
│         if wasTrackingLocation {
│             backgroundSession = CLBackgroundActivitySession()
│             startLocationUpdates()
│         }
│
└─ NO → Check authorization level

Q5: What is authorization level?
├─ .authorizedWhenInUse → This is fine with CLBackgroundActivitySession
│   The blue indicator allows background access
│
├─ .authorizedAlways → Should work, check session lifecycle
│
└─ .denied → No background access possible

Common Mistakes

// ❌ WRONG: Local variable deallocates immediately
func startTracking() {
    let session = CLBackgroundActivitySession()  // Dies at end of function!
    startLocationUpdates()
}

// ✅ RIGHT: Property keeps session alive
var backgroundSession: CLBackgroundActivitySession?

func startTracking() {
    backgroundSession = CLBackgroundActivitySession()
    startLocationUpdates()
}

Symptom 3: Authorization Always Denied

Decision Tree

Q1: Is this a fresh install or returning user?
├─ FRESH INSTALL with immediate denial → Check Info.plist strings
│   Missing/empty NSLocationWhenInUseUsageDescription = automatic denial
│
└─ RETURNING USER → Check previous denial

Q2: Did user previously deny?
├─ YES → User must manually re-enable in Settings
│   Fix: Show UI explaining value, with button to open Settings:
│        UIApplication.shared.open(URL(string: UIApplication.openSettingsURLString)!)
│
└─ NO → Check next

Q3: Are you requesting authorization at wrong time?
├─ Requesting when app not "in use" → insufficientlyInUse
│   Check: update.insufficientlyInUse or diagnostic.insufficientlyInUse
│   Fix: Only request authorization from foreground, during user interaction
│
└─ NO → Check next

Q4: Is device in restricted mode?
├─ YES → .restricted status (parental controls, MDM)
│   Fix: Cannot override. Offer manual location input.
│
└─ NO → Check Info.plist again

Q5: Are Info.plist strings compelling?
├─ Generic string → Users more likely to deny
│   Bad: "This app needs your location"
│   Good: "Your location helps us show restaurants within walking distance"
│
└─ Review: Look at string from user's perspective

Info.plist String Best Practices

<!-- ❌ BAD: Vague, no value proposition -->
<key>NSLocationWhenInUseUsageDescription</key>
<string>We need your location.</string>

<!-- ✅ GOOD: Specific benefit to user -->
<key>NSLocationWhenInUseUsageDescription</key>
<string>Your location helps show restaurants, coffee shops, and attractions within walking distance.</string>

<!-- ❌ BAD: No explanation for Always -->
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>We need your location always.</string>

<!-- ✅ GOOD: Explains background benefit -->
<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>Enable background location to receive reminders when you arrive at saved places, even when the app is closed.</string>

Symptom 4: Location Accuracy Unexpectedly Poor

Quick Checks

// 1. Check accuracy authorization
let accuracy = CLLocationManager().accuracyAuthorization
print("Accuracy auth: \(accuracy == .fullAccuracy ? "full" : "reduced")")

// 2. Check update's accuracy flag (iOS 17+)
for try await update in CLLocationUpdate.liveUpdates() {
    if update.accuracyLimited {
        print("Accuracy limited - updates every 15-20 min")
    }
    if let location = update.location {
        print("Horizontal accuracy: \(location.horizontalAccuracy)m")
    }
}

Decision Tree

Q1: What is accuracyAuthorization?
├─ .reducedAccuracy → User chose approximate location
│   Options:
│   1. Accept reduced accuracy (weather, city-level features)
│   2. Request temporary full accuracy:
│      CLServiceSession(authorization: .whenInUse, fullAccuracyPurposeKey: "Navigation")
│   3. Explain value and link to Settings
│
└─ .fullAccuracy → Check environment and configuration

Q2: What is horizontalAccuracy on locations?