how to get accurate speed in android

static float[] dist1 = new float[1];

Location location = null;
static LocationManager locationmanager;

static double  avg_distance = 0.0;

locationmanager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

location = locationmanager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location == null) {
location = locationmanager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
}
if (location == null) {
location = locationmanager
.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
}
if (location != null) {
pre_Latitude = location.getLatitude();
pre_Lognitude = location.getLongitude();

}

try {
if (pre_lat_long == 2) {
String pre_lat = getSharedPreferences("TEXT", 0)
.getString("prelat", null);
String pre_long = getSharedPreferences("TEXT", 0)
.getString("prelog", null);
pre_Latitude = Double.valueOf(pre_lat);
pre_Lognitude = Double.valueOf(pre_long);
Log.e("locationpp", "" + pre_Latitude + ".."
+ pre_Lognitude);
}
} catch (Exception e) {
// TODO: handle exception
Log.e("error", e.getMessage().toString());
}

Double lat = 0.00, log = 0.00;
if (location != null) {
lat = location.getLatitude();
log = location.getLongitude();
Log.e("loca", "" + lat + ".." + log);
}

if (pre_lat_long == 0) {

pre_Latitude = lat;
pre_Lognitude = log;
pre_lat_long = 2;
}

present_Longitude = log;
present_Latitude = lat;
SharedPreferences shp = getSharedPreferences("TEXT", 0);
final Editor editor = shp.edit();
editor.putString("prelat", "" + lat);
editor.putString("prelog", "" + log);
editor.commit();


Location.distanceBetween(present_Latitude, present_Longitude,
pre_Latitude, pre_Lognitude, dist1);
double miles = dist1[0] * 0.00062137119;
total_times = location.getTime();
distance = distance + miles;
                               String Distance_string_1 = "" + distance;

         avg_distance = ((distance_cover_*3600)/totaltime_in_sec)*0.621371;