Improving Accuracy of The Gps Updates

Question

i am using the follwing code to start and set the location manager parameters

    self.locationManager = [[CLLocationManager alloc] init];
 self.locationManager.delegate = self;
 self.locationManager.distanceFilter = kCLDistanceFilterNone; 
 self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
 [locationManager startUpdatingLocation];

and then i am getting the updates in the method - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {

and i am calculating the distance the user has travelled by using the successive location, in the starting itself i am getting the distance of 1000 meters where i have not even moved 100 meters, this might be due to erroneous location i think.

can anybody suggest how to improve the accuracy.