根据道路计算两个位置之间的距离

Question

I have two MKCoordinateRegion objects. Based on values from those objects I make two annotations on map. Then I calculate distance between those two locations:

CLLocationCoordinate2D pointACoordinate = [ann coordinate];
    CLLocation *pointALocation = [[CLLocation alloc] initWithLatitude:pointACoordinate.latitude longitude:pointACoordinate.longitude];  

    CLLocationCoordinate2D pointBCoordinate = [ann2 coordinate];
    CLLocation *pointBLocation = [[CLLocation alloc] initWithLatitude:pointBCoordinate.latitude longitude:pointBCoordinate.longitude];  

    float distanceMeters = [pointBLocation distanceFromLocation:pointALocation];

    distanceMeters = distanceMeters / 1000;

But I ma not sure that values I get is correct.
Are those values air distance?
Is it possible to get distance based on roads ?
I need distance that user must pass with car.

Answer 1

Theses values are air distance.

You can't find the distance based on roads with the Apple SDK. Try to ask directly to google APIs http://code.google.com/intl/fr-FR/apis/maps/index.html

Answer 2

Use CLLocation instead of CLLocationCoordinate:-

CLLocation has an init method named

-(id)initWithLatitude:(CLLocationDegrees)latitude longitude:(CLLocationDegrees)longitude. 

Then use

- (CLLocationDistance)getDistanceFrom:(const CLLocation *)location 

to get the distance between two CLLocation objects on Road.

The Distance you will get is in kilometers.

Answer 3

Since iOS7 you can get that info with this:

+ (void)distanceByRoadFromPoint:(CLLocationCoordinate2D)fromPoint
                        toPoint:(CLLocationCoordinate2D)toPoint
              completionHandler:(MKDirectionsHandler)completionHandler {

    MKDirectionsRequest *request = [[MKDirectionsRequest alloc] init];
    request.transportType = MKDirectionsTransportTypeAutomobile;

    request.source = [self mapItemFromCoordinate:fromPoint];
    request.destination = [self mapItemFromCoordinate:toPoint];

    MKDirections *directions = [[MKDirections alloc] initWithRequest:request];
    [directions calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse * routeResponse, NSError *routeError) {

         MKRoute *route = [routeResponse.routes firstObject];
         CLLocationDistance distance = route.distance;
         NSTimeInterval expectedTime = route.expectedTravelTime;

         //call a completion handler that suits your situation

     }];    

   }


+ (MKMapItem *)mapItemFromCoordinate:(CLLocationCoordinate2D)coordinate {

    MKPlacemark *placemark = [[MKPlacemark alloc] initWithCoordinate:coordinate addressDictionary:nil];
    MKMapItem *item = [[MKMapItem alloc] initWithPlacemark:placemark];

    return item;

}

Answer 4

what @coolanilkothari says is almost correct almost except for the fact that getDistanceFrom is deprecated in ios 3.2. This is what the apple docs have to say..

getDistanceFrom:

Returns the distance (in meters) from the receiver's location to the specified location. (Deprecated in iOS 3.2. Use the distanceFromLocation: method instead.) - (CLLocationDistance)getDistanceFrom:(const CLLocation *)location Parameters

location

 The other location. 

Return Value

The distance (in meters) between the two locations. Discussion

This method measures the distance between the two locations by tracing a line between them that follows the curvature of the Earth. The resulting arc is a smooth curve and does not take into account specific altitude changes between the two locations. Availability

 Available in iOS 2.0 and later. Deprecated in iOS 3.2. 

Declared In CLLocation.h

Answer 5

you have to just pass origin and destination co-ordinate and then parse the result.

http://maps.googleapis.com/maps/api/distancematrix/xml?origins=Vancouver+BC&destinations=San+Francisco&sensor=false