Android - Gps location change distance

Question

I am trying to make a Speedometer app that will get location every 5 sec interval. calculate the distance and get the user velocity, but my initial data is showing a high value firstly without even moving the phone and than then being kind of random value. please check my code.

MainActivity.java

    public class MainActivity extends Activity {


        private static final int REQUEST_CODE_PERMISSION = 2;
        String mPermission = Manifest.permission.ACCESS_FINE_LOCATION;

        TextView tvRunning, tvMax;
        int maxv = 0;
        // GPSTracker class
        GPSTracker gps;
        GPSTracker GPSTrackerBefore = new GPSTracker(MainActivity.this);

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            tvRunning = (TextView) findViewById(R.id.tvRunnung);
            tvMax = (TextView) fin

dViewById(R.id.tvMax);
        try {
            if (ActivityCompat.checkSelfPermission(this, mPermission)
                    != MockPackageManager.PERMISSION_GRANTED) {

                ActivityCompat.requestPermissions(this, new String[]{mPermission},
                        REQUEST_CODE_PERMISSION);

                // If any permission above not allowed by user, this condition will
                //execute every time,else your else part will work
            }
        } catch (Exception e) {

            e.printStackTrace();
        }
        //----------------initializing the first gps----------------//
        if(GPSTrackerBefore.canGetLocation){
            GPSTrackerBefore.getLocation();
        }

        final Handler ha = new Handler();
        ha.postDelayed(new Runnable() {

            @Override
            public void run() {
                //call function
[enter image description here][1]

                gps = new GPSTracker(MainActivity.this);

                // check if GPS enabled
                if (gps.canGetLocation()) {

                    double lon2 = gps.getLongitude(), lat2 = gps.getLatitude();
                    double lon1 = GPSTrackerBefore.getLongitude(), lat1 = GPSTrackerBefore.getLatitude();

                    int R = 6371; // km
                    double x = (lon2 - lon1) * Math.cos((lat1 + lat2) / 2);
                    double y = (lat2 - lat1);
                    int d = (int) Math.sqrt(x * x + y * y) * R;
                    int v=d/5; //this is the velocity  divided by interval time
                    Toast.makeText(getApplicationContext(), String.valueOf(v), Toast.LENGTH_SHORT).show();
//                    Toast.makeText(getApplicationContext(),
//                            gps.getLatitude()+"||"+gps.getLongitude()+
//                                    "\n"+GPSTrackerBefore.getLatitude()+"||"+GPSTrackerBefore.getLongitude(),
//                                        Toast.LENGTH_SHORT).show();
                    GPSTrackerBefore = gps;

                    tvRunning.setText(String.valueOf(v));
                    if (v > maxv) {
                        maxv = v;
                        tvMax.setText(String.valueOf(maxv));
                    }

                } else {
                    // can't get location
                    // GPS or Network is not enabled
                    // Ask user to enable GPS/network in settings
                    gps.showSettingsAlert();
                }

                ha.postDelayed(this, 5000);
            }
        }, 5000);


    }

}

GPSTracker.java

package bytebiters.com.speedo;


public class GPSTracker extends Service implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    boolean isGPSEnabled = false;

    // flag for network status
    boolean isNetworkEnabled = false;

    // flag for GPS status
    boolean canGetLocation = false;

    Location location; // location
    double latitude; // latitude
    double longitude; // longitude

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 1; // 1 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 3000 ; // 1 sec

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GPSTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);

            // getting GPS status
            isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

            // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (!isGPSEnabled && !isNetworkEnabled) {
                // no network provider is enabled
            } else {
                this.canGetLocation = true;
                // First get location from Network Provider
                if (isNetworkEnabled) {
                    locationManager.requestLocationUpdates(
                            LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);

                    Log.d("Network", "Network");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }

                // if GPS Enabled get lat/long using GPS Services
                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);

                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {
                            location = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);

                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                            }
                        }
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return location;
    }

    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */

    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(GPSTracker.this);
        }
    }

    /**
     * Function to get latitude
     * */

    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    /**
     * Function to get longitude
     * */

    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/wifi enabled
     * @return boolean
     * */

    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */

    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

        // Setting Dialog Message
        alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }
}

Answer 1

In GPSTracker, attempting to read latitude or longitude will return 0 if there is no location available. You need multiple readings before you attempt to estimate speed using your method.

Code aside, GPS coordinates are inherently noisy (the position is not known exactly). There will always be errors in a speed measurement that result from noise in the position estimation. There are more sophisticated methods for estimating speed and location from noisy measurements such as the Kalman Filter.