Merge branch 'barometer#10' into main

src/main/java/de/dennisguse/opentracks/util/PressureSensorUtils.java

@@ -0,0 +1,83 @@
+package de.dennisguse.opentracks.util;
+
+import android.hardware.SensorManager;
+
+public class PressureSensorUtils {
+
+    //Everything above is considered a meaningful change in elevation.
+    private static float ELEVATION_CHANGE_DIFF_M = 3.0f;
+
+    private static float EXPONENTIAL_SMOOTHING = 0.3f;
+
+    private PressureSensorUtils() {
+    }
+
+    public static class ElevationChange {
+
+        private float currentSensorValue_hPa;
+
+        private float elevationChange_m;
+
+        public ElevationChange(float currentSensorValue_hPa, float elevationChange_m) {
+            this.currentSensorValue_hPa = currentSensorValue_hPa;
+            this.elevationChange_m = elevationChange_m;
+        }
+
+        public float getCurrentSensorValue_hPa() {
+            return currentSensorValue_hPa;
+        }
+
+        public float getElevationChange_m() {
+            return elevationChange_m;
+        }
+
+        public float getElevationGain_m() {
+            return elevationChange_m > 0 ? elevationChange_m : 0;
+        }
+
+        public float getElevationLoss_m() {
+            return elevationChange_m < 0 ? elevationChange_m : 0;
+        }
+    }
+
+    /**
+     * Applies exponential smoothing to sensor value before computation.
+     */
+    public static ElevationChange computeChangesWithSmoothing_m(float lastAcceptedSensorValue_hPa, float lastSeenSensorValue_hPa, float currentSensorValue_hPa) {
+        float nextSensorValue_hPa = EXPONENTIAL_SMOOTHING * currentSensorValue_hPa + (1 - EXPONENTIAL_SMOOTHING) * lastSeenSensorValue_hPa;
+
+        return computeChanges_m(lastAcceptedSensorValue_hPa, nextSensorValue_hPa);
+    }
+
+    /**
+     * Computes the elevation gain and elevation loss.
+     *
+     * @return null if no meaningful elevation change occurred.
+     */
+    public static ElevationChange computeChanges_m(float lastAcceptedSensorValue_hPa, float currentSensorValue_hPa) {
+        float lastSensorValue_m = SensorManager.getAltitude(SensorManager.PRESSURE_STANDARD_ATMOSPHERE, lastAcceptedSensorValue_hPa);
+        float currentSensorValue_m = SensorManager.getAltitude(SensorManager.PRESSURE_STANDARD_ATMOSPHERE, currentSensorValue_hPa);
+
+        float elevationChange_m = currentSensorValue_m - lastSensorValue_m;
+        if (Math.abs(elevationChange_m) < ELEVATION_CHANGE_DIFF_M) {
+            return null;
+        }
+
+        // Limit elevation change by ELEVATION_CHANGE_DIFF and computes pressure value accordingly.
+        ElevationChange elevationChange = new ElevationChange(currentSensorValue_hPa, elevationChange_m);
+        if (elevationChange.getElevationGain_m() > 0) {
+            return new ElevationChange(getBarometricPressure(SensorManager.PRESSURE_STANDARD_ATMOSPHERE, lastSensorValue_m + ELEVATION_CHANGE_DIFF_M), ELEVATION_CHANGE_DIFF_M);
+        } else {
+            return new ElevationChange(getBarometricPressure(SensorManager.PRESSURE_STANDARD_ATMOSPHERE, lastSensorValue_m - ELEVATION_CHANGE_DIFF_M), -1 * ELEVATION_CHANGE_DIFF_M);
+        }
+    }
+
+    /*
+     * Barometeric pressure to elevation estimation; inverts of SensorManager.getAltitude(float, float)
+     * https://de.wikipedia.org/wiki/Barometrische_H%C3%B6henformel#Internationale_H%C3%B6henformel
+     * {\color{White} p(h)} = p_0 \cdot \left( 1 - \frac{0{,}0065 \frac{\mathrm K}{\mathrm m} \cdot h}{T_0\ } \right)^{5{,}255}
+     */
+    private static float getBarometricPressure(float p0, float altitude_m) {
+        return (float) (p0 * Math.pow(1.0 - 0.0065 * altitude_m / 288.15, 5.255f));
+    }
+}

src/main/java/de/dennisguse/opentracks/util/StringUtils.java

@@ -323,21 +323,21 @@ public class StringUtils {
     }
 
     /**
-     * Sets an elevation value.
+     * Sets an elevation_m value.
      *
      * @param context     the context
-     * @param elevation   the elevation in meters
+     * @param elevation_m the elevation_m
      * @param metricUnits true if metric units
-     * @return the formatted elevation (or null) and it's unit as {@link Pair}
+     * @return the formatted elevation_m (or null) and it's unit as {@link Pair}
      */
-    public static Pair<String, String> formatElevation(Context context, double elevation, boolean metricUnits) {
+    public static Pair<String, String> formatElevation(Context context, Float elevation_m, boolean metricUnits) {
         String value = context.getString(R.string.value_unknown);
         String unit = context.getString(metricUnits ? R.string.unit_meter : R.string.unit_feet);
-        if (!Double.isNaN(elevation) && !Double.isInfinite(elevation)) {
+        if (elevation_m != null) {
             if (!metricUnits) {
-                elevation *= UnitConversions.M_TO_FT;
+                elevation_m *= (float) UnitConversions.M_TO_FT;
             }
-            value = StringUtils.formatDecimal(elevation, 0);
+            value = StringUtils.formatDecimal(elevation_m, 0);
         }
         return new Pair<>(value, unit);
     }

src/main/java/de/dennisguse/opentracks/util/UnitConversions.java

@@ -26,7 +26,8 @@ public class UnitConversions {
     public static final long S_TO_MS = 1000;
 
     // Time
-    // 1 second in milliseconds
+    // TODO Use int instead of long.
+    public static final long ONE_SECOND_US = UnitConversions.S_TO_MS * 1000;
     public static final long ONE_SECOND_MS = UnitConversions.S_TO_MS;
     public static final long ONE_MINUTE_MS = (long) (UnitConversions.MIN_TO_S * UnitConversions.S_TO_MS);
     public static final long ONE_HOUR_MS = 60 * ONE_MINUTE_MS;