SGS III 上的指南针读数 [英] Compass readings on SGS III

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本文介绍了SGS III 上的指南针读数的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

我的应用程序需要使用其指南针显示设备的当前方位.我使用的代码(如下)在我的 Galaxy Nexus 和 Galaxy One 上运行良好,但指南针在三星 Galaxy S III 上疯狂旋转.我试过做一个数字 8 来重新校准设备,但这并没有改变任何东西.奇怪的是,从 Google Play 下载的其他指南针应用程序在 SIII 上运行良好.这可能是什么问题?

My app needs to show the current bearing of the device using its compass. The code I'm using (below) works perfectly fine on my Galaxy Nexus and Galaxy One, but the compass is spinning around wildly on a Samsung Galaxy S III. I've tried doing a figure-8 to recalibrate the device, but that doesn't change anything. The weird thing is that other compass apps downloaded from Google Play work just fine on the SIII. What could be the issue here?

float[] mGravity;
float[] mGeomagnetic;

public void onSensorChanged( SensorEvent event ) {
    float azimuth = 0f;
    if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
        mGravity = event.values;
    if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
        mGeomagnetic = event.values;
    if (mGravity != null && mGeomagnetic != null) {
        float R[] = new float[9];
        float I[] = new float[9];
        boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);
        if (success) {
            float orientation[] = new float[3];
            SensorManager.getOrientation(R, orientation);
            azimuth = orientation[0]; // orientation contains: azimut, pitch and roll
        }
     }

    //Discard 0.0-values
    if(azimuth == 0.0) { return; }

    //Convert the sensor value to degrees
    azimuth = (float) Math.toDegrees(azimuth); //same as azimuth = -azimuth*360/(2*3.14159f);


    //Smooth the sensor-output
    azimuth = smoothValues(azimuth);
}

//From http://stackoverflow.com/questions/4699417/android-compass-orientation-on-unreliable-low-pass-filter
//SmoothFactorCompass: The easing float that defines how smooth the movement will be (1 is no smoothing and 0 is never updating, my default is 0.5).
//SmoothThresholdCompass: The threshold in which the distance is big enough to turn immediately (0 is jump always, 360 is never jumping, my default is 30).
static final float SmoothFactorCompass = 0.5f;
static final float SmoothThresholdCompass = 30.0f;
float oldCompass = 0.0f;
private float smoothValues (float newCompass){
    if (Math.abs(newCompass - oldCompass) < 180) {
        if (Math.abs(newCompass - oldCompass) > SmoothThresholdCompass) {
            oldCompass = newCompass;
        }
        else {
            oldCompass = oldCompass + SmoothFactorCompass * (newCompass - oldCompass);
        }
    }
    else {
        if (360.0 - Math.abs(newCompass - oldCompass) > SmoothThresholdCompass) {
            oldCompass = newCompass;
        }
        else {
            if (oldCompass > newCompass) {
                oldCompass = (oldCompass + SmoothFactorCompass * ((360 + newCompass - oldCompass) % 360) + 360) % 360;
            } 
            else {
                oldCompass = (oldCompass - SmoothFactorCompass * ((360 - newCompass + oldCompass) % 360) + 360) % 360;
            }
        }
    }
    return oldCompass;
}

推荐答案

目前我正在研究 Android 上的罗盘机制,我建议您从低通滤波器开始.您需要做的是对 ACCELEROMETER 和 MAGNETIC_FIELD 传感器数据应用低通滤波器.这是我如何实现的:

Currently I am investigating compass mechanism on Android and I would recommend to start with low-pass filter in your case. What you need to do - is to apply low-pass filter to both ACCELEROMETER and MAGNETIC_FIELD sensors data. Here is how I implemented that:

private float[] accel;
private float[] geomagnetic;
float R[] = new float[9];
float I[] = new float[9];
float orientation[] = new float[3];

@Override
public void onSensorChanged(SensorEvent event)
{
    synchronized (this)
    {
        float azimuth = -1f;

        if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
            accel = lowPass( event.values.clone(), accel );

        if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
            geomagnetic = lowPass(event.values.clone(), geomagnetic);

        if (accel != null && geomagnetic != null)
        {

            boolean success = SensorManager.getRotationMatrix(R, I,
                    accel, geomagnetic);

            SensorManager.remapCoordinateSystem(R,
                    SensorManager.AXIS_X, SensorManager.AXIS_Z, R);

            if (success)
            {
                SensorManager.getOrientation(R, orientation);
                azimuth = orientation[0]; // orientation contains:
                                         // azimuth, pitch
                                         // and roll
                float newHeading = azimuth * 360 / (2 * 3.14159f);

                //do what you need to do with new heading
            } 
        }
    }
}


/*
 * time smoothing constant for low-pass filter 0 ≤ alpha ≤ 1 ; a smaller
 * value basically means more smoothing See:
 * http://en.wikipedia.org/wiki/Low-pass_filter#Discrete-time_realization
 */
static final float ALPHA = 0.15f;

/**
 * @see http
 *      ://en.wikipedia.org/wiki/Low-pass_filter#Algorithmic_implementation
 * @see http
 *      ://developer.android.com/reference/android/hardware/SensorEvent.html
 *      #values
 */

protected float[] lowPass(float[] input, float[] output)
{
    if (output == null)
        return input;

    for (int i = 0; i < input.length; i++)
    {
        output[i] = output[i] + ALPHA * (input[i] - output[i]);
    }
    return output;
}

这篇关于SGS III 上的指南针读数的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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