Android accelerometer integration to determine speed and position

Question

I am trying to calculate the offset using an accelerometer on an Android device ( Sensor.TYPE_LINEAR_ACCELERATION). Here is my method OnSensorChanged():

public void onSensorChanged(SensorEvent event) {
    accelX = event.values[0];
    accelY = event.values[1];
    accelZ = event.values[2];

    long currentTime = System.currentTimeMillis() / 1000;

    if(prevTime == 0) prevTime = currentTime;

    long interval = currentTime - prevTime;
    prevTime = currentTime;     

    velX += accelX * interval;
    velY += accelY * interval;
    velZ += accelZ * interval;

    distX += prevVelX + velX * interval;
    distY += prevVelY + velY * interval;
    distZ += prevVelZ + velZ * interval;

    prevAccelX = accelX;        
    prevAccelY = accelY;        
    prevAccelZ = accelZ;

    prevVelX = velX;
    prevVelY = velY;
    prevVelZ = velZ;
}

The speed, however, does not return to 0 after any movement. Slowing has little effect if it is not very unexpected. This leads to some very inaccurate distance values.

The accelerometer is also very noisy, so I added the following:

accelX = (accelX * accelKFactor) + prevAccelX * (1 - accelKFactor);
accelY = (accelY * accelKFactor) + prevAccelY * (1 - accelKFactor);
accelY = (accelX * accelKFactor) + prevAccelY * (1 - accelKFactor);

Where accelKFactor= .01

Am I missing something obvious?

My ultimate goal is to simply say if the device was moved more than 10 feet or not, but now my data is practically useless.

EDIT:

. currentTime , 1000, . , 1 . currentTime double , .

Answer 1

SensorEvent , . System.currentTimeMillis(). :

private static final float NS2S = 1.0f / 1000000000.0f;
 private float timestamp;

 public void onSensorChanged(SensorEvent event) {
      // This timestep delta rotation to be multiplied by the current rotation
      // after computing it from the gyro sample data.
      if (timestamp != 0) {
          final float dT = (event.timestamp - timestamp) * NS2S;

, .

, Location.getSpeed ​​(). , .