我正在尝试在我的 Android 手机 (Nexus 4) 上制作一个应用程序，该应用程序将用于模型船。我添加了低通滤波器来过滤掉传感器中的 gitter。
但是，指南针只有在手机平放时才能稳定。如果我将它向上倾斜(例如翻一页书)，那么指南针的航向就会偏离 - 多达 50*。
我已经用 Sensor.TYPE_MAGNETIC_FIELD 和 Sensor.TYPE_GRAVITY 和 Sensor.TYPE_ACCELEROMETER 尝试过这个，效果是一样的。
我使用了提到的解决方案 here ，以及许多其他地方。我的数学不是很好，但这一定是一个常见问题，我发现没有 API 可以处理它，这让我很沮丧。
我已经解决这个问题 3 天了，仍然没有找到任何解决方案，但是当我使用 Compass from Catch 时，无论手机倾斜多少，它们都保持稳定。所以我知道这一定是可能的。
我要做的就是创建一个指南针，如果手机指向北方，那么指南针将读取北方，并且当手机通过任何其他轴(滚动或俯仰)移动时不会跳来跳去。
在我不得不放弃我的项目之前，谁能帮忙。
谢谢， 亚当
最佳答案
巧合的是，我已经考虑这个问题好几个星期了，因为
- 作为一名数学家，我对所看到的任何答案都不满意在别处建议；并且
- 我需要为我正在开发的应用程序提供一个好的答案。
我已经把我正在使用的数学 here on math.stackexchange.com ，并且我已经粘贴了我在下面使用的代码。该代码根据原始 TYPE_GRAVITY 和 TYPE_MAGNETIC_FIELD 传感器数据计算方位角和俯仰角，无需任何 API 调用，例如SensorManager.getRotationMatrix(...) 或 SensorManager.getOrientation(...)。代码可能会得到改进，例如如果输入有点不稳定，则使用低通滤波器。请注意，代码通过 onAccuracyChanged(Sensor sensor, int accuracy) 方法记录传感器的精度，因此如果方位角看起来不稳定，另一件要检查的是每个传感器的精度。在任何情况下，所有计算都在此代码中明确可见，如果存在不稳定性问题(当传感器精度合理时)，则可以通过查看输入或方向向量中的不稳定性来解决这些问题 m_NormGravityVector[ ]、m_NormEastVector[] 或 m_NormNorthVector[]。
我会对任何人对这种方法的任何反馈都非常感兴趣。我发现它在我自己的应用程序中就像做梦一样，只要设备是平面朝上、垂直或介于两者之间的。但是，正如我在 math.stackexchange.com 文章中提到的那样，当设备接近倒置时会出现一些问题。在这种情况下，需要仔细定义自己想要的行为。
import android.app.Activity;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.view.Surface;
public static class OrientationSensor implements SensorEventListener {
public final static int SENSOR_UNAVAILABLE = -1;
// references to other objects
SensorManager m_sm;
SensorEventListener m_parent; // non-null if this class should call its parent after onSensorChanged(...) and onAccuracyChanged(...) notifications
Activity m_activity; // current activity for call to getWindowManager().getDefaultDisplay().getRotation()
// raw inputs from Android sensors
float m_Norm_Gravity; // length of raw gravity vector received in onSensorChanged(...). NB: should be about 10
float[] m_NormGravityVector; // Normalised gravity vector, (i.e. length of this vector is 1), which points straight up into space
float m_Norm_MagField; // length of raw magnetic field vector received in onSensorChanged(...).
float[] m_NormMagFieldValues; // Normalised magnetic field vector, (i.e. length of this vector is 1)
// accuracy specifications. SENSOR_UNAVAILABLE if unknown, otherwise SensorManager.SENSOR_STATUS_UNRELIABLE, SENSOR_STATUS_ACCURACY_LOW, SENSOR_STATUS_ACCURACY_MEDIUM or SENSOR_STATUS_ACCURACY_HIGH
int m_GravityAccuracy; // accuracy of gravity sensor
int m_MagneticFieldAccuracy; // accuracy of magnetic field sensor
// values calculated once gravity and magnetic field vectors are available
float[] m_NormEastVector; // normalised cross product of raw gravity vector with magnetic field values, points east
float[] m_NormNorthVector; // Normalised vector pointing to magnetic north
boolean m_OrientationOK; // set true if m_azimuth_radians and m_pitch_radians have successfully been calculated following a call to onSensorChanged(...)
float m_azimuth_radians; // angle of the device from magnetic north
float m_pitch_radians; // tilt angle of the device from the horizontal. m_pitch_radians = 0 if the device if flat, m_pitch_radians = Math.PI/2 means the device is upright.
float m_pitch_axis_radians; // angle which defines the axis for the rotation m_pitch_radians
public OrientationSensor(SensorManager sm, SensorEventListener parent) {
m_sm = sm;
m_parent = parent;
m_activity = null;
m_NormGravityVector = m_NormMagFieldValues = null;
m_NormEastVector = new float[3];
m_NormNorthVector = new float[3];
m_OrientationOK = false;
}
public int Register(Activity activity, int sensorSpeed) {
m_activity = activity; // current activity required for call to getWindowManager().getDefaultDisplay().getRotation()
m_NormGravityVector = new float[3];
m_NormMagFieldValues = new float[3];
m_OrientationOK = false;
int count = 0;
Sensor SensorGravity = m_sm.getDefaultSensor(Sensor.TYPE_GRAVITY);
if (SensorGravity != null) {
m_sm.registerListener(this, SensorGravity, sensorSpeed);
m_GravityAccuracy = SensorManager.SENSOR_STATUS_ACCURACY_HIGH;
count++;
} else {
m_GravityAccuracy = SENSOR_UNAVAILABLE;
}
Sensor SensorMagField = m_sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
if (SensorMagField != null) {
m_sm.registerListener(this, SensorMagField, sensorSpeed);
m_MagneticFieldAccuracy = SensorManager.SENSOR_STATUS_ACCURACY_HIGH;
count++;
} else {
m_MagneticFieldAccuracy = SENSOR_UNAVAILABLE;
}
return count;
}
public void Unregister() {
m_activity = null;
m_NormGravityVector = m_NormMagFieldValues = null;
m_OrientationOK = false;
m_sm.unregisterListener(this);
}
@Override
public void onSensorChanged(SensorEvent evnt) {
int SensorType = evnt.sensor.getType();
switch(SensorType) {
case Sensor.TYPE_GRAVITY:
if (m_NormGravityVector == null) m_NormGravityVector = new float[3];
System.arraycopy(evnt.values, 0, m_NormGravityVector, 0, m_NormGravityVector.length);
m_Norm_Gravity = (float)Math.sqrt(m_NormGravityVector[0]*m_NormGravityVector[0] + m_NormGravityVector[1]*m_NormGravityVector[1] + m_NormGravityVector[2]*m_NormGravityVector[2]);
for(int i=0; i < m_NormGravityVector.length; i++) m_NormGravityVector[i] /= m_Norm_Gravity;
break;
case Sensor.TYPE_MAGNETIC_FIELD:
if (m_NormMagFieldValues == null) m_NormMagFieldValues = new float[3];
System.arraycopy(evnt.values, 0, m_NormMagFieldValues, 0, m_NormMagFieldValues.length);
m_Norm_MagField = (float)Math.sqrt(m_NormMagFieldValues[0]*m_NormMagFieldValues[0] + m_NormMagFieldValues[1]*m_NormMagFieldValues[1] + m_NormMagFieldValues[2]*m_NormMagFieldValues[2]);
for(int i=0; i < m_NormMagFieldValues.length; i++) m_NormMagFieldValues[i] /= m_Norm_MagField;
break;
}
if (m_NormGravityVector != null && m_NormMagFieldValues != null) {
// first calculate the horizontal vector that points due east
float East_x = m_NormMagFieldValues[1]*m_NormGravityVector[2] - m_NormMagFieldValues[2]*m_NormGravityVector[1];
float East_y = m_NormMagFieldValues[2]*m_NormGravityVector[0] - m_NormMagFieldValues[0]*m_NormGravityVector[2];
float East_z = m_NormMagFieldValues[0]*m_NormGravityVector[1] - m_NormMagFieldValues[1]*m_NormGravityVector[0];
float norm_East = (float)Math.sqrt(East_x * East_x + East_y * East_y + East_z * East_z);
if (m_Norm_Gravity * m_Norm_MagField * norm_East < 0.1f) { // Typical values are > 100.
m_OrientationOK = false; // device is close to free fall (or in space?), or close to magnetic north pole.
} else {
m_NormEastVector[0] = East_x / norm_East; m_NormEastVector[1] = East_y / norm_East; m_NormEastVector[2] = East_z / norm_East;
// next calculate the horizontal vector that points due north
float M_dot_G = (m_NormGravityVector[0] *m_NormMagFieldValues[0] + m_NormGravityVector[1]*m_NormMagFieldValues[1] + m_NormGravityVector[2]*m_NormMagFieldValues[2]);
float North_x = m_NormMagFieldValues[0] - m_NormGravityVector[0] * M_dot_G;
float North_y = m_NormMagFieldValues[1] - m_NormGravityVector[1] * M_dot_G;
float North_z = m_NormMagFieldValues[2] - m_NormGravityVector[2] * M_dot_G;
float norm_North = (float)Math.sqrt(North_x * North_x + North_y * North_y + North_z * North_z);
m_NormNorthVector[0] = North_x / norm_North; m_NormNorthVector[1] = North_y / norm_North; m_NormNorthVector[2] = North_z / norm_North;
// take account of screen rotation away from its natural rotation
int rotation = m_activity.getWindowManager().getDefaultDisplay().getRotation();
float screen_adjustment = 0;
switch(rotation) {
case Surface.ROTATION_0: screen_adjustment = 0; break;
case Surface.ROTATION_90: screen_adjustment = (float)Math.PI/2; break;
case Surface.ROTATION_180: screen_adjustment = (float)Math.PI; break;
case Surface.ROTATION_270: screen_adjustment = 3*(float)Math.PI/2; break;
}
// NB: the rotation matrix has now effectively been calculated. It consists of the three vectors m_NormEastVector[], m_NormNorthVector[] and m_NormGravityVector[]
// calculate all the required angles from the rotation matrix
// NB: see https://math.stackexchange.com/questions/381649/whats-the-best-3d-angular-co-ordinate-system-for-working-with-smartfone-apps
float sin = m_NormEastVector[1] - m_NormNorthVector[0], cos = m_NormEastVector[0] + m_NormNorthVector[1];
m_azimuth_radians = (float) (sin != 0 && cos != 0 ? Math.atan2(sin, cos) : 0);
m_pitch_radians = (float) Math.acos(m_NormGravityVector[2]);
sin = -m_NormEastVector[1] - m_NormNorthVector[0]; cos = m_NormEastVector[0] - m_NormNorthVector[1];
float aximuth_plus_two_pitch_axis_radians = (float)(sin != 0 && cos != 0 ? Math.atan2(sin, cos) : 0);
m_pitch_axis_radians = (float)(aximuth_plus_two_pitch_axis_radians - m_azimuth_radians) / 2;
m_azimuth_radians += screen_adjustment;
m_pitch_axis_radians += screen_adjustment;
m_OrientationOK = true;
}
}
if (m_parent != null) m_parent.onSensorChanged(evnt);
}
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
int SensorType = sensor.getType();
switch(SensorType) {
case Sensor.TYPE_GRAVITY: m_GravityAccuracy = accuracy; break;
case Sensor.TYPE_MAGNETIC_FIELD: m_MagneticFieldAccuracy = accuracy; break;
}
if (m_parent != null) m_parent.onAccuracyChanged(sensor, accuracy);
}
}
关于可以补偿倾斜和俯仰的 Android 指南针，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16317599/