Location manager accuracy not very accurate

Question

I am having an issue with sending location to other users. I using Parse.com as my backend and I use this code to get a location:

-(void)sendLocation{



    if ([locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)]){

        [locationManager requestWhenInUseAuthorization];

    }
    [locationManager startUpdatingLocation];



}


- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    [locationManager stopUpdatingLocation]; //kill it NOW or we have duplicates

    if(!self.haveLocation) {

        self.haveLocation=YES;

        NSLog(@"didUpdateToLocation: %@", newLocation);

        self.currentLocation = newLocation;
        self.currentLocationGeoPoint= [PFGeoPoint geoPointWithLocation:self.currentLocation];

}

If I send myself a message from my current location and then open the message to view it, by comparing the current location circle with the pin dropped I can see they aren't in the same place and a fair distance apart.

I have the BOOL var haveLocation to make sure it is only refreshed once. Do I need to refresh it more times or something? Any pointers on how to make this more accurate would be really appreciated! Thanks

I tried following the apple example LocateMe:

I now have:

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{

    NSTimeInterval locationAge = -[newLocation.timestamp timeIntervalSinceNow];

    if (locationAge > 5.0) return;

    // test that the horizontal accuracy does not indicate an invalid measurement
    if (newLocation.horizontalAccuracy < 0) return;

    // test the measurement to see if it is more accurate than the previous measurement
    if (self.bestEffortAtLocation == nil || self.bestEffortAtLocation.horizontalAccuracy > newLocation.horizontalAccuracy) {
        // store the location as the "best effort"
        self.bestEffortAtLocation = newLocation;


        if (newLocation.horizontalAccuracy <= locationManager.desiredAccuracy) {

            [locationManager stopUpdatingLocation];

            //this code after getting the location
            NSLog(@"didUpdateToLocation: %@", newLocation);
}

}

}

However when I tap send location it just runs forever and doesn't stop updating.. I have locationManager.desiredAccuracy = kCLLocationAccuracyBest; set too.

Answer 1

The location manager may send you several updates as it improves its accuracy. This is a feature designed to give you information it as as quickly as possible, while eventually getting the best information to you (at least up to the accuracy you requested). You are actively avoiding those updates, so you are likely getting the least accurate information.

You should check the horizontalAccuracy to determine if it is accurate enough for your use.

Note that you cannot compare horizontalAccuracy to kCLLocationAccuracyBest. "Best" is a constant -1. You need to compare it to what you need (in meters), and probably set a timeout to give up if it takes too long to get there (the system may not be able to provide you an arbitrarily accurate value.)