Can't get location from Wifi connection on iPhone - iphone

Question

I am trying to write an app that will get a users location for a mass transit app which works great when I am above ground. When I am underground the location doesn't update even if I have a wifi and/or a cell signal. Below is the code that I am using. From what I understood the iPhone is able to get a location from wifi signal only, is this incorrect? Any help would be greatly appreciated, thank you in advance!
- (void)viewDidLoad
{
[super viewDidLoad];
//********************** Add map ******************************************
//setup location manager
locationManager = [[CLLocationManager alloc] init];
[locationManager setDelegate:self];
[locationManager setDistanceFilter:kCLDistanceFilterNone];
[locationManager setDesiredAccuracy:kCLLocationAccuracyHundredMeters];
//setup map view
mapView = [[MKMapView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 160.0f)];
mapView.showsUserLocation = YES;
mapView.userTrackingMode = MKUserTrackingModeFollow;
//run loop in background
loopTimer = [[NSTimer scheduledTimerWithTimeInterval:timeInterval target:self selector:#selector(tick:) userInfo:nil repeats:YES]retain];
}
// Search for n seconds to get the best location during that time
- (void) tick: (NSTimer *) timer
{
// Check for valid coordinate
CLLocationCoordinate2D coord = mapView.userLocation.location.coordinate;
if (!coord.latitude && !coord.longitude) return;
//get coordinates to update map
[mapView setRegion:MKCoordinateRegionMake(coord, MKCoordinateSpanMake(0.005f, 0.005f)) animated:NO];
//update current location in view
currentLatView.text = [NSString stringWithFormat:#"%.2f", coord.latitude];
currentLonView.text = [NSString stringWithFormat:#"%.1f", coord.longitude];
}

Answer 1

The locationManager you setup in viewDidLoad is your instance of the CL Location Manager whereas MapKit uses its own instance when you set showsUserLocation to true.
So your settings for the distance filter and desired accuracy are not being used by MapKit, and in any case, you haven't started your location manager with startUpdatingLocation.
So, try starting your location manager instance and then use the delegate method
locationManager:(CLLocationManager *)manager didUpdateToLocation:
to get what your location manager says.

Answer 2

Here is what I came up with, seems to work well needs more testing.
- (void)viewDidLoad
{
[super viewDidLoad];
//********************** Add map ******************************************
// Create the manager object
self.locationManager = [[[CLLocationManager alloc] init] autorelease];
locationManager.delegate = self;
// This is the most important property to set for the manager. It ultimately determines how the manager will
// attempt to acquire location and thus, the amount of power that will be consumed.
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
// When "tracking" the user, the distance filter can be used to control the frequency with which location measurements
// are delivered by the manager. If the change in distance is less than the filter, a location will not be delivered.
locationManager.distanceFilter = kCLLocationAccuracyBest;
// Once configured, the location manager must be "started".
[locationManager startUpdatingLocation];
//initialize newCoord
currentCoord = [[CLLocation alloc] initWithLatitude:0 longitude:0];
//setup map view
mapView = [[MKMapView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 160.0f)];
mapView.showsUserLocation = YES;
mapView.userTrackingMode = MKUserTrackingModeFollow;
//create map view
[self.view addSubview:mapView];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
// test that the horizontal accuracy does not indicate an invalid measurement
if (newLocation.horizontalAccuracy < 0) return;
// test the age of the location measurement to determine if the measurement is cached
// in most cases you will not want to rely on cached measurements
NSTimeInterval locationAge = -[newLocation.timestamp timeIntervalSinceNow];
if (locationAge > 5.0) return;
// store all of the measurements, just so we can see what kind of data we might receive
currentCoord = newLocation;
[self tick];
}
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
// The location "unknown" error simply means the manager is currently unable to get the location.
if ([error code] != kCLErrorLocationUnknown) {
[self stopUpdatingLocation:NSLocalizedString(#"Error", #"Error")];
}
}
- (void)stopUpdatingLocation:(NSString *)state
{
[locationManager stopUpdatingLocation];
locationManager.delegate = nil;
}
- (void) tick
{
//do stuff here
}