計算真正在Android的

Question

我的要求正確航向像Google maps apps羅盤模式軸承（你可以看到演示時點擊current location button twice）：

• 在這個compass模式下，地圖總是一個角度，使旋轉bluedot arrow始終指向頂部屏幕。

但我不知道如何從azimuth, pitch, roll值計算正確的bearing。

public void onSensorChanged(SensorEvent sensorEvent) { 
     switch (sensorEvent.sensor.getType()) { 
      case Sensor.TYPE_ACCELEROMETER: 
       System.arraycopy(sensorEvent.values, 0, mAccelerometers, 0, 3); 
       break; 
      case Sensor.TYPE_MAGNETIC_FIELD: 
       System.arraycopy(sensorEvent.values, 0, mMagnetometers, 0, 3); 
       break; 
      default: 
       break; 
     } 
     float[] rotationMatrix = new float[9]; 
     boolean success = 
        SensorManager.getRotationMatrix(rotationMatrix, null, mAccelerometers, mMagnetometers); 
     if (success) { 
      SensorManager.getOrientation(rotationMatrix, mOrientation); 
      float azimuth = Math.toDegrees(mOrientation[0]); 
      float pitch = Math.toDegrees(mOrientation[1]); 
      float roll = Math.toDegrees(mOrientation[2]); 
     } 
     // cal to updateBearing(); 
    } 

在iOS中，CLHeading可以返回準確真實heading。 android中是否有一個班級具有相同的功能？我該如何計算它？

Answer 1

檢查下面的鏈接爲您的問題軸承例子也回答以下

bearing-example

是similor您的問題。

How do I get the correct bearing?

package ymc.ch.bearingexample; 
import android.content.Context; 
import android.hardware.GeomagneticField; 
import android.hardware.Sensor; 
import android.hardware.SensorEvent; 
import android.hardware.SensorEventListener; 
import android.hardware.SensorManager; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.os.Bundle; 
import android.util.Log; 

/** 
* Utility class that provides bearing values to true north. 
*/ 
public class BearingToNorthProvider implements SensorEventListener, LocationListener 
{ 
    public static final String TAG = "BearingToNorthProvider"; 

    /** 
    * Interface definition for a callback to be invoked when the bearing changes. 
    */ 
    public static interface ChangeEventListener { 
     /** 
     * Callback method to be invoked when the bearing changes. 
     * @param bearing the new bearing value 
     */ 
     void onBearingChanged(double bearing); 
    } 

    private final SensorManager mSensorManager; 
    private final LocationManager mLocationManager; 
    private final Sensor mSensorAccelerometer; 
    private final Sensor mSensorMagneticField; 

    // some arrays holding intermediate values read from the sensors, used to calculate our azimuth 
    // value 

    private float[] mValuesAccelerometer; 
    private float[] mValuesMagneticField; 
    private float[] mMatrixR; 
    private float[] mMatrixI; 
    private float[] mMatrixValues; 

    /** 
    * minimum change of bearing (degrees) to notify the change listener 
    */ 
    private final double mMinDiffForEvent; 

    /** 
    * minimum delay (millis) between notifications for the change listener 
    */ 
    private final double mThrottleTime; 

    /** 
    * the change event listener 
    */ 
    private ChangeEventListener mChangeEventListener; 

    /** 
    * angle to magnetic north 
    */ 
    private AverageAngle mAzimuthRadians; 

    /** 
    * smoothed angle to magnetic north 
    */ 
    private double mAzimuth = Double.NaN; 

    /** 
    * angle to true north 
    */ 
    private double mBearing = Double.NaN; 

    /** 
    * last notified angle to true north 
    */ 
    private double mLastBearing = Double.NaN; 

    /** 
    * Current GPS/WiFi location 
    */ 
    private Location mLocation; 

    /** 
    * when we last dispatched the change event 
    */ 
    private long mLastChangeDispatchedAt = -1; 

    /** 
    * Default constructor. 
    * 
    * @param context Application Context 
    */ 
    public BearingToNorthProvider(Context context) { 
     this(context, 10, 0.5, 50); 
    } 

    /** 
    * @param context Application Context 
    * @param smoothing the number of measurements used to calculate a mean for the azimuth. Set 
    *      this to 1 for the smallest delay. Setting it to 5-10 to prevents the 
    *      needle from going crazy 
    * @param minDiffForEvent minimum change of bearing (degrees) to notify the change listener 
    * @param throttleTime minimum delay (millis) between notifications for the change listener 
    */ 
    public BearingToNorthProvider(Context context, int smoothing, double minDiffForEvent, int throttleTime) 
    { 
     mSensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE); 
     mSensorAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
     mLocationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE); 
     mSensorMagneticField = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD); 

     mValuesAccelerometer = new float[3]; 
     mValuesMagneticField = new float[3]; 

     mMatrixR = new float[9]; 
     mMatrixI = new float[9]; 
     mMatrixValues = new float[3]; 

     mMinDiffForEvent = minDiffForEvent; 
     mThrottleTime = throttleTime; 

     mAzimuthRadians = new AverageAngle(smoothing); 
    } 

    //============================================================================================== 
    // Public API 
    //============================================================================================== 

    /** 
    * Call this method to start bearing updates. 
    */ 
    public void start() 
    { 
     mSensorManager.registerListener(this, mSensorAccelerometer, SensorManager.SENSOR_DELAY_UI); 
     mSensorManager.registerListener(this, mSensorMagneticField, SensorManager.SENSOR_DELAY_UI); 

     for (final String provider : mLocationManager.getProviders(true)) { 
      if (LocationManager.GPS_PROVIDER.equals(provider) 
        || LocationManager.PASSIVE_PROVIDER.equals(provider) 
        || LocationManager.NETWORK_PROVIDER.equals(provider)) { 
       if (mLocation == null) { 
        mLocation = mLocationManager.getLastKnownLocation(provider); 
       } 
       mLocationManager.requestLocationUpdates(provider, 0, 100.0f, this); 
      } 
     } 
    } 

    /** 
    * call this method to stop bearing updates. 
    */ 
    public void stop() 
    { 
     mSensorManager.unregisterListener(this, mSensorAccelerometer); 
     mSensorManager.unregisterListener(this, mSensorMagneticField); 
     mLocationManager.removeUpdates(this); 
    } 

    /** 
    * @return current bearing 
    */ 
    public double getBearing() 
    { 
     return mBearing; 
    } 

    /** 
    * Returns the bearing event listener to which bearing events must be sent. 
    * @return the bearing event listener 
    */ 
    public ChangeEventListener getChangeEventListener() 
    { 
     return mChangeEventListener; 
    } 

    /** 
    * Specifies the bearing event listener to which bearing events must be sent. 
    * @param changeEventListener the bearing event listener 
    */ 
    public void setChangeEventListener(ChangeEventListener changeEventListener) 
    { 
     this.mChangeEventListener = changeEventListener; 
    } 

    //============================================================================================== 
    // SensorEventListener implementation 
    //============================================================================================== 

    @Override 
    public void onSensorChanged(SensorEvent event) 
    { 
     switch (event.sensor.getType()) { 
      case Sensor.TYPE_ACCELEROMETER: 
       System.arraycopy(event.values, 0, mValuesAccelerometer, 0, 3); 
       break; 
      case Sensor.TYPE_MAGNETIC_FIELD: 
       System.arraycopy(event.values, 0, mValuesMagneticField, 0, 3); 
       break; 
     } 

     boolean success = SensorManager.getRotationMatrix(mMatrixR, mMatrixI, 
       mValuesAccelerometer, 
       mValuesMagneticField); 

     // calculate a new smoothed azimuth value and store to mAzimuth 
     if (success) { 
      SensorManager.getOrientation(mMatrixR, mMatrixValues); 
      mAzimuthRadians.putValue(mMatrixValues[0]); 
      mAzimuth = Math.toDegrees(mAzimuthRadians.getAverage()); 
     } 

     // update mBearing 
     updateBearing(); 
    } 

    @Override 
    public void onAccuracyChanged(Sensor sensor, int i) { } 

    //============================================================================================== 
    // LocationListener implementation 
    //============================================================================================== 

    @Override 
    public void onLocationChanged(Location location) 
    { 
     // set the new location 
     this.mLocation = location; 

     // update mBearing 
     updateBearing(); 
    } 

    @Override 
    public void onStatusChanged(String s, int i, Bundle bundle) { } 

    @Override 
    public void onProviderEnabled(String s) { } 

    @Override 
    public void onProviderDisabled(String s) { } 

    //============================================================================================== 
    // Private Utilities 
    //============================================================================================== 

    private void updateBearing() 
    { 
     if (!Double.isNaN(this.mAzimuth)) { 
      if(this.mLocation == null) { 
       Log.w(TAG, "Location is NULL bearing is not true north!"); 
       mBearing = mAzimuth; 
      } else { 
       mBearing = getBearingForLocation(this.mLocation); 
      } 

      // Throttle dispatching based on mThrottleTime and minDiffForEvent 
      if(System.currentTimeMillis() - mLastChangeDispatchedAt > mThrottleTime && 
       (Double.isNaN(mLastBearing) || Math.abs(mLastBearing - mBearing) >= mMinDiffForEvent)) { 
       mLastBearing = mBearing; 
       if(mChangeEventListener != null) { 
        mChangeEventListener.onBearingChanged(mBearing); 
       } 
       mLastChangeDispatchedAt = System.currentTimeMillis(); 
      } 
     } 
    } 

    private double getBearingForLocation(Location location) 
    { 
     return mAzimuth + getGeomagneticField(location).getDeclination(); 
    } 

    private GeomagneticField getGeomagneticField(Location location) 
    { 
     GeomagneticField geomagneticField = new GeomagneticField(
       (float)location.getLatitude(), 
       (float)location.getLongitude(), 
       (float)location.getAltitude(), 
       System.currentTimeMillis()); 
     return geomagneticField; 
    } 
} 

Answer 2

方位角

和位置來計算標題唯一需要的參數。

的角度進行計算和轉換的約定是按以下順序使用它們：
1）方位角
2）間距
3）輥

Answer 3

要計算一個標題，你只需要方位。正如你已經證明，它是values[0]從調用返回到SensorManager.getOrientation

然後，從弧度轉換爲度，並確保它的積極意義：

float current_measured_bearing = (float) (results[0] * 180/Math.PI); 
if (current_measured_bearing < 0) current_measured_bearing += 360; 

更多細節this answer，其中還考慮了effect of device orientation。