Added elevation loss via barometer (like elevation gain). Fixes #547.

src/main/java/de/dennisguse/opentracks/services/TrackRecordingService.java

@@ -665,6 +665,7 @@ public class TrackRecordingService extends Service implements HandlerServer.Hand
         try {
             if (elevationSumManager != null) {
                 trackPoint.setElevationGain(elevationSumManager.getElevationGain_m());
+                trackPoint.setElevationLoss(elevationSumManager.getElevationLoss_m());
                 elevationSumManager.reset();
             }
             contentProviderUtils.insertTrackPoint(trackPoint, track.getId());
@@ -680,7 +681,6 @@ public class TrackRecordingService extends Service implements HandlerServer.Hand
         voiceExecutor.update();
     }
 
-
     /**
      * Updates the recording track time.
      *
@@ -718,6 +718,17 @@ public class TrackRecordingService extends Service implements HandlerServer.Hand
         return elevationSumManager.getElevationGain_m();
     }
 
+    /**
+     * Returns the relative elevation loss (since last trackpoint).
+     */
+    Float getElevationLoss_m() {
+        if (elevationSumManager == null || !elevationSumManager.isConnected()) {
+            return null;
+        }
+
+        return elevationSumManager.getElevationLoss_m();
+    }
+
     private void showNotification(boolean isGpsStarted) {
         if (isRecording()) {
             Intent intent = IntentUtils.newIntent(this, TrackRecordingActivity.class)

src/main/java/de/dennisguse/opentracks/services/TrackRecordingServiceBinder.java

@@ -104,6 +104,11 @@ class TrackRecordingServiceBinder extends android.os.Binder implements TrackReco
         return trackRecordingService.getElevationGain_m();
     }
 
+    @Override
+    public Float getElevationLoss_m() {
+        return trackRecordingService.getElevationLoss_m();
+    }
+
     @VisibleForTesting
     @Override
     public void setRemoteSensorManager(BluetoothRemoteSensorManager remoteSensorManager) {

src/main/java/de/dennisguse/opentracks/services/TrackRecordingServiceInterface.java

@@ -78,6 +78,13 @@ public interface TrackRecordingServiceInterface {
      */
     Float getElevationGain_m();
 
+    /**
+     * Gets the current elevation loss.
+     *
+     * @return elevation loss in m or null.
+     */
+    Float getElevationLoss_m();
+
     @VisibleForTesting
     void setRemoteSensorManager(BluetoothRemoteSensorManager remoteSensorManager);
 

src/main/java/de/dennisguse/opentracks/services/sensors/ElevationSumManager.java

@@ -112,6 +112,6 @@ public class ElevationSumManager implements SensorEventListener {
 
         lastSeenSensorValue_hPa = value_hPa;
 
-        Log.v(TAG, "elevation gain: " + elevationGain_m);
+        Log.v(TAG, "elevation gain: " + elevationGain_m + ", elevation loss: " + elevationLoss_m);
     }
 }