android - 朝拜指南针不正确或不准确

Question

首先获取当前位置以北，然后计算方位，

这是代码：

  @Override
        public void onSensorChanged(SensorEvent event) {
float azimuth = (int)event.values[0];
            azimuth =  azimuth * 180 / (float) Math.PI;
GeomagneticField geoField = new GeomagneticField(Double.valueOf(
                    location.getLatitude()).floatValue(), Double.valueOf(
                    location.getLongitude()).floatValue(), Double.valueOf(
                    location.getAltitude()).floatValue(),
                    System.currentTimeMillis());

            azimuth += geoField.getDeclination(); // converts magnetic north
                                                    // into true north
            float bearing = location.bearingTo(MeccaLocation); // (it's already
                                                                // in degrees)

float Meccadirection = (float) (azimuth - bearing);
} 

但结果方向不准确。