how to count step using accelerometer in android

Question

i need to count no of steps while walking. so that i am using accelerometer. in the above coding i get accelerometer sensor's x,y,z values. this is i have done so far. my problems is by the x,y,z how to count steps while walking? i get the following code from the link

http://pedometer.googlecode.com/svn/trunk/src/name/bagi/levente/pedometer/Pedometer.java

my code:

 import android.app.Activity;  import android.content.Context;  import android.os.Bundle;  import android.widget.TextView;  import android.widget.Toast;   public class Accelerometer extends Activity implements AccelerometerListener {  private static Context CONTEXT;  /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);     CONTEXT = this; }  protected void onResume() {     super.onResume();     if (AccelerometerManager.isSupported()) {         AccelerometerManager.startListening(this);     } }  protected void onDestroy() {     super.onDestroy();     if (AccelerometerManager.isListening()) {         AccelerometerManager.stopListening();     }  }  public static Context getContext() {     return CONTEXT; }  /**  * onShake callback  */ public void onShake(float force) {     Toast.makeText(this, "Phone shaked : " + force, 1000).show(); }  /**  * onAccelerationChanged callback  */ public void onAccelerationChanged(float x, float y, float z) {     ((TextView) findViewById(R.id.x)).setText(String.valueOf(x));     ((TextView) findViewById(R.id.y)).setText(String.valueOf(y));     ((TextView) findViewById(R.id.z)).setText(String.valueOf(z)); }   } 

please help me.

Answer 1

You will not find here a simple code to just count steps (it is just too complex). But there's info out there if you're interested:

• There are good diagrams and step analyses here (in pdf).

• You can find a more formal publication here: http://portal.acm.org/citation.cfm?id=1554235

• And if you want to create a sensitive pedometer (proposed for the elderly), I suggest you to start from this paper: http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4575030

Answer 2

You can estimate the gravity force on the phone using the x,y,z values...

float g = (x * x + y * y + z * z) / (SensorManager.GRAVITY_EARTH * SensorManager.GRAVITY_EARTH); 

...here a value of 1 = normal (1g is normal)

The a crude pedometer can be built fairly easily by just counting how many peaks above a specified g value over a given sample period (eg 6 seconds and multiple by 10 for paces per minute)

Say for example record the time in ms that a g of >2 is recorded... then the peak will continue going up.... and come back down below 2.. probably to 0.5 or something.. then it'll go up again >2... at this point stop the clock.

...then you have a complete cycle timed!

To stabilise the result it's better to count a few cycles.