iPhone GPS CoreLocation to get accurate reading quickly - swift

Question

I'm new to GPS and using CoreLocation to narrow a user's position down to ideally 2m. I've read somewhere that iPhone GPS coordinates accurate up to 4m, but I'm trying a few things to improve the accuracy reading.
My current solution
involves setting a 70 second window to average a list of up to 3 coordinates, and replacing them as newer more accurate readings come in. The averaged coordinate jumps around for about a minute before landing within an ~8m (observed) vicinity of the true location.
Select code blocks below:
...
locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
locationManager.distanceFilter = kCLDistanceFilterNone
...
var timer = 70
func startTracking() {
var _ = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(countdown), userInfo: nil, repeats: true)
}
#objc func countdown() { self.timer -= 1 }
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
// 70 seconds to pin down verify location
if self.timer <= 1 {return}
if let oldLoc = locationDataService.initialLocationEstimate {
updateInitialLocation(newLocation: self.locationManager.location!)
}
}
...
updateInitialLocationEstimate() {
let newLocationAccuracy = newLocation.horizontalAccuracy
if self.initialLocationAccuracy != nil {
// don't use if greater than 12m and less accurate.
if newLocationAccuracy > self.initialLocationAccuracy! && newLocationAccuracy > 8 {
return
} else if newLocation.horizontalAccuracy < initialLocationAccuracy! {
// eliminates the less accurate readings
trimByAccuracy(locations: &self.initialLocationEstimates, newAccuracy: newLocationAccuracy)
self.initialLocationAccuracy = newLocationAccuracy
}
if (self.initialLocationEstimates.count > 4) {
initialLocationEstimates.removeFirst()
}
} else {
self.initialLocationAccuracy = newLocationAccuracy
}
self.initialLocationEstimates.append(newLocation)
self.initialLocationEstimate = estimateCentralCoordinate(locations: initialLocationEstimates, accuracy: initialLocationAccuracy!)
}
I'm struggling on a few things:
1) Half the time it takes to get an >4m (observed) accuracy rating. Currently, it takes about a minute to get an ~8m reading. Is there anything I can do?
2) Improve observed accuracy. Anything suggestions would be helpful here.
3) It has been suggested to me to use Kalman Filters, but the velocity given to me by CoreLocation is iffy. While I'm standing still, it frequently fluctuates between +/- 0-1m/s, is there some setting that I'm not aware of to stabilize the readings?
4) Should I be averaging/filtering at all? I've read that good GPS software already does averages, but I've come across nothing on the iOS CoreLocation documentation.
Really, any help would be appreciated. Thanks.