Reduce location resource usage: economy mode by default, lifecycle throttling

- Start LocationService at ECONOMY (5 s, PRIORITY_BALANCED_POWER_ACCURACY)
  instead of FULL (1 Hz, PRIORITY_HIGH_ACCURACY); promote to FULL only
  while a track is actively recording and demote back when recording stops
- Use PRIORITY_BALANCED_POWER_ACCURACY for ECONOMY and ANCHOR_WATCH modes
  so the GPS chip idles and network/passive sources handle light-duty fixes
- Add ACTION_START_ECONOMY / ACTION_START_FULL intents so MainActivity can
  drive mode transitions from lifecycle callbacks
- onPause: drop to ECONOMY if not recording or anchor-watching; onResume:
  restore the appropriate mode so the first visible frame has a fresh rate
- Stop-anchor-watch now returns to ECONOMY instead of FULL (anchor drop
  rarely coincides with active track recording)
- Remove ACCESS_BACKGROUND_LOCATION from manifest — the foreground service
  with foregroundServiceType="location" already covers background access
- Add 5 m minimum-distance filter to DeviceGpsProvider so stationary devices
  don't generate spurious location callbacks

https://claude.ai/code/session_01YUbuZNDAoLea4cf9UGQ9qn

4 files changed, 50 insertions, 7 deletions

diff --git a/android-app/app/src/main/AndroidManifest.xml b/android-app/app/src/main/AndroidManifest.xml
index a10d503..5090190 100644
--- a/android-app/app/src/main/AndroidManifest.xml
+++ b/android-app/app/src/main/AndroidManifest.xml
@@ -3,7 +3,6 @@
 
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
-    <uses-permission android:name="android.permission.ACCESS_BACKGROUND_LOCATION" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_LOCATION" />
     <uses-permission android:name="android.permission.INTERNET" />
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/LocationService.kt b/android-app/app/src/main/kotlin/org/terst/nav/LocationService.kt
index 18e0907..015e334 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/LocationService.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/LocationService.kt
@@ -236,8 +236,8 @@ class LocationService : Service() {
             ACTION_START_FOREGROUND_SERVICE -> {
                 startForeground(NOTIFICATION_ID, createNotification())
                 serviceScope.launch {
-                    _currentPowerMode.emit(PowerMode.FULL)
-                    startLocationUpdatesInternal(PowerMode.FULL)
+                    _currentPowerMode.emit(PowerMode.ECONOMY)
+                    startLocationUpdatesInternal(PowerMode.ECONOMY)
                 }
                 barometerSensorManager.start()
                 val flags = (application as NavApplication).featureFlags
@@ -251,6 +251,8 @@ class LocationService : Service() {
                 nmeaStreamManager.stop()
                 stopSelf()
             }
+            ACTION_START_ECONOMY -> setPowerMode(PowerMode.ECONOMY)
+            ACTION_START_FULL    -> setPowerMode(PowerMode.FULL)
             ACTION_START_ANCHOR_WATCH -> {
                 val radius = intent.getDoubleExtra(EXTRA_WATCH_RADIUS, AnchorWatchState.DEFAULT_WATCH_CIRCLE_RADIUS_METERS)
                 serviceScope.launch {
@@ -260,7 +262,7 @@ class LocationService : Service() {
             }
             ACTION_STOP_ANCHOR_WATCH -> {
                 stopAnchorWatch()
-                setPowerMode(PowerMode.FULL)
+                setPowerMode(PowerMode.ECONOMY)
             }
             ACTION_UPDATE_WATCH_RADIUS -> {
                 val radius = intent.getDoubleExtra(EXTRA_WATCH_RADIUS, AnchorWatchState.DEFAULT_WATCH_CIRCLE_RADIUS_METERS)
@@ -297,7 +299,11 @@ class LocationService : Service() {
 
     @SuppressLint("MissingPermission")
     private fun startLocationUpdatesInternal(powerMode: PowerMode) {
-        val locationRequest = LocationRequest.Builder(Priority.PRIORITY_HIGH_ACCURACY, powerMode.gpsUpdateIntervalMillis)
+        val priority = if (powerMode == PowerMode.FULL)
+            Priority.PRIORITY_HIGH_ACCURACY
+        else
+            Priority.PRIORITY_BALANCED_POWER_ACCURACY
+        val locationRequest = LocationRequest.Builder(priority, powerMode.gpsUpdateIntervalMillis)
             .setMinUpdateIntervalMillis(powerMode.gpsUpdateIntervalMillis / 2)
             .build()
         fusedLocationClient.requestLocationUpdates(
@@ -378,6 +384,8 @@ class LocationService : Service() {
     companion object {
         const val ACTION_START_FOREGROUND_SERVICE = "ACTION_START_FOREGROUND_SERVICE"
         const val ACTION_STOP_FOREGROUND_SERVICE = "ACTION_STOP_FOREGROUND_SERVICE"
+        const val ACTION_START_ECONOMY = "ACTION_START_ECONOMY"
+        const val ACTION_START_FULL    = "ACTION_START_FULL"
         const val ACTION_START_ANCHOR_WATCH = "ACTION_START_ANCHOR_WATCH"
         const val ACTION_STOP_ANCHOR_WATCH = "ACTION_STOP_ANCHOR_WATCH"
         const val ACTION_UPDATE_WATCH_RADIUS = "ACTION_UPDATE_WATCH_RADIUS"
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
index 8609456..05dbf12 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/MainActivity.kt
@@ -112,6 +112,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
 
     private val viewModel: MainViewModel by viewModels()
     private var pendingServiceStart = false
+    private var serviceStarted = false
 
     override fun onResume() {
         super.onResume()
@@ -119,9 +120,17 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
         if (pendingServiceStart) {
             pendingServiceStart = false
             startServices()
+        } else {
+            restoreLocationMode()
         }
     }
 
+    override fun onPause() {
+        super.onPause()
+        if (!NavApplication.isTesting) mapView?.onPause()
+        throttleLocationIfIdle()
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         MapLibre.getInstance(this)
@@ -449,6 +458,25 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
         finishAffinity()
     }
 
+    private fun locationServiceIntent(action: String) =
+        Intent(this, LocationService::class.java).apply { this.action = action }
+
+    /** Drop to economy rate when the app goes to the background and nothing needs precision. */
+    private fun throttleLocationIfIdle() {
+        if (!serviceStarted) return
+        if (!viewModel.isRecording.value && !LocationService.anchorWatchState.value.isActive) {
+            startService(locationServiceIntent(LocationService.ACTION_START_ECONOMY))
+        }
+    }
+
+    /** On return to foreground: restore full accuracy if recording, otherwise economy. */
+    private fun restoreLocationMode() {
+        if (!serviceStarted) return
+        val action = if (viewModel.isRecording.value) LocationService.ACTION_START_FULL
+                     else LocationService.ACTION_START_ECONOMY
+        startService(locationServiceIntent(action))
+    }
+
     override fun onActivateMob() {
         lifecycleScope.launch {
             LocationService.locationFlow.firstOrNull()?.let { gpsData ->
@@ -519,6 +547,7 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
         }
 
     private fun startServices() {
+        serviceStarted = true
         val intent = Intent(this, LocationService::class.java).apply {
             action = LocationService.ACTION_START_FOREGROUND_SERVICE
         }
@@ -658,6 +687,13 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
 
     private fun observeDataSources() {
         startThermalMonitoring()
+        lifecycleScope.launch {
+            viewModel.isRecording.collect { recording ->
+                val action = if (recording) LocationService.ACTION_START_FULL
+                             else LocationService.ACTION_START_ECONOMY
+                startService(locationServiceIntent(action))
+            }
+        }
         var conditionsLoaded = false
         lifecycleScope.launch {
             LocationService.locationFlow.collect { gpsData ->
@@ -801,7 +837,6 @@ class MainActivity : AppCompatActivity(), SafetyFragment.SafetyListener {
     }
 
     override fun onStart() { super.onStart(); if (!NavApplication.isTesting) mapView?.onStart() }
-    override fun onPause() { super.onPause(); if (!NavApplication.isTesting) mapView?.onPause() }
     override fun onStop() { super.onStop(); if (!NavApplication.isTesting) mapView?.onStop() }
     override fun onDestroy() { super.onDestroy(); if (!NavApplication.isTesting) mapView?.onDestroy(); stopThermalAlarm() }
     override fun onLowMemory() { super.onLowMemory(); if (!NavApplication.isTesting) mapView?.onLowMemory() }
diff --git a/android-app/app/src/main/kotlin/org/terst/nav/gps/DeviceGpsProvider.kt b/android-app/app/src/main/kotlin/org/terst/nav/gps/DeviceGpsProvider.kt
index f2a4e59..a8d46e4 100644
--- a/android-app/app/src/main/kotlin/org/terst/nav/gps/DeviceGpsProvider.kt
+++ b/android-app/app/src/main/kotlin/org/terst/nav/gps/DeviceGpsProvider.kt
@@ -56,7 +56,7 @@ class DeviceGpsProvider(
         locationManager.requestLocationUpdates(
             LocationManager.GPS_PROVIDER,
             updateIntervalMs,
-            0f,
+            MIN_UPDATE_DISTANCE_METERS,
             locationListener,
             Looper.getMainLooper()
         )
@@ -83,5 +83,6 @@ class DeviceGpsProvider(
 
     companion object {
         private const val FIX_LOST_TIMEOUT_MS = 10_000L
+        private const val MIN_UPDATE_DISTANCE_METERS = 5f
     }
 }