iOS：使用 CLLocationManager 获得准确的反向地理编码？

Question

背景：我想让用户在需要时在几秒钟内获得他们的位置。但是，位置大多是不准确的。我想询问用户是否愿意再试一次以获得更准确的地址。

问题：如何编写代码以保证下一次猜测总是比上一次猜测更好。

我尝试过的：

CLLocationManager *locationManager;

- (CLLocationManager *)locationManager {
    if (locationManager != nil) {
        return locationManager;
    }
    locationManager = [[CLLocationManager alloc] init];
    [locationManager setDesiredAccuracy:kCLLocationAccuracyBest];
    [locationManager setDelegate:self];
    return locationManager;
}

-(void)myLocationClickedWithCount: (int) count{
    [[self locationManager] startUpdatingLocation];
    CLLocation *location = [locationManager location];
    CLGeocoder *locationGeocoded = [[CLGeocoder alloc] init];
    [locationGeocoded reverseGeocodeLocation:location completionHandler:^(NSArray *placemarks, NSError *error) {
        CLPlacemark *placemark = [placemarks objectAtIndex:0];
        if (!placemark){
            if (count > 0){
                //placemark not available, try again after 1 second
                sleep(1);
                [self myLocationClickedWithCount:count-1];
            }
            else{
                //Unable to get location after 3 tries
                UIAlertView *locationNotFoundAlert = [[UIAlertView alloc]initWithTitle:@"Unable to Locate" message:@"Would you like to try again?" delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil];
                locationNotFoundAlert.tag = locationNotFoundAlertTag;
                [locationNotFoundAlert show];
            }
        }else{
            // got location but not accurate.
            if (location.horizontalAccuracy > accuracyRadius) {
                UIAlertView *locationInaccurateAlert = [[UIAlertView alloc]initWithTitle:@"Inaccurate Location" message:[NSString stringWithFormat:@"Your GPS shows the radius of %.2f meters. Would you like to try again?",location.horizontalAccuracy] delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil];
                locationInaccurateAlert.tag = locationInaccurateAlertTag;
                [locationInaccurateAlert show];
            }else {
                address.text = placemark;
            }
        }
    }];
}

---

更新 当用户再次询问时，猜测可能需要更长的时间。我只是想知道我应该如何编码。 IE：我应该再打电话给[[self locationManager] startUpdatingLocation]; 吗？还是会重置我到目前为止的位置。因此，如何根据 GPS 的当前信息来改进我的第二次猜测（GPS 开启时间越长，准确度就越高？）。

Answer 1

关于通过代码的准确性，您无能为力...除了

   [locationManager setDesiredAccuracy:kCLLocationAccuracyBest];

你已经完成了... 据我所见，如果您使用的是 3G 或 EDGE，那么您的准确度会大大提高（可以达到 5-10m 的准确度水平）。

您可以参考 Apple 的 this 文章，该文章讨论了 iphone GPS 精度的工作原理......

希望这会有所帮助..