Getting wrong distance between locations in iOS?

Question

Hi aim using following method to find out the distance between my current location and the locations(lat and longitude) stored in NSMutableArray value.

But am getting wrong distance..Please help..

My code

    -(void)getDistancetoShow:(NSMutableArray *)newArray{

    CLLocationCoordinate2D coordinateUser = [self getLocation];


    float _lat,_long;


  first_Loc = [[CLLocation alloc] initWithLatitude:coordinateUser.latitude longitude:coordinateUser.longitude];

    for(int p=0;p<[[newArray1 valueForKey:@"Name"] count];p++){

        _lat=[[[newArray1 valueForKey:@"Latitude"] objectAtIndex:p]floatValue];
         _long=[[[newArray1 valueForKey:@"Longitude"] objectAtIndex:p]floatValue];
        second_loc=[[CLLocation alloc] initWithLatitude:_lat longitude:_long];


        showDistance=[second_loc distanceFromLocation:first_Loc]/1000;

        [distanceToDispaly addObject:[NSString stringWithFormat:@"%.2f KM",showDistance]];
    }

     NSLog(@"first=%@, second=%@", first_Loc, second_loc);


}

Latitudes in array

( "47.0735010448824", "47.0564688100431", " 47.0582514311038", "47.0587640538326", "47.0569233603454", "47.0541853132569", "47.0542029215138", "47.0544259594592", "47.0560264547367", " 47.0576532159776", " 47.0550023679218", "47.0342030007379", "47.0746263896213", " 47.0740256635512", "47.0524765957921", "47.0606287049051", "47.0539691521825", "47.0542799159057", "47.0651001682846", "47.0536948902097", "47.0525973335309", "47.0389265414812", "47.0761811267051", "47.0668801601942", "47.0614859079241", "47.0579433468181", "47.0718998779465" )

and longitude in array

( "21.9154175327011", "21.9312065669748", "21.9337414545594", " 21.9346772505188", " 21.9300587945685", "21.9363460105132", "21.9362081709222", "21.9343042603097", "21.939485335992", "21.9320057169724", "21.9300799002643", "21.9485373571669", "21.9310667367526", "21.9318507902135", "21.9192195298473", "21.9195273899529", "21.9329595191441", "21.9292015418841", "21.9219452321208", "21.9098849252041", "21.9074768948561", "21.9424499491422", "21.9151458954504", "21.9304346568769", "21.9305973807911", "21.9331511189507", "21.9159872752442" )

but the real distance in something like staring with 9**** but am getiing now 5***

Answer 1

CLLocation gives you crow(straight) distance between two places. I thinks you are getting crow distance.

First take coordinate of two places and find distance between them. then search crow distance between those two coordinate.

hope this will help

Answer 2

Once you get the two coordinates you can calculate the distance between them using this piece of code (taken from here):

- (NSNumber*)calculateDistanceInMetersBetweenCoord:(CLLocationCoordinate2D)coord1 coord:(CLLocationCoordinate2D)coord2 {
    NSInteger nRadius = 6371; // Earth's radius in Kilometers
    double latDiff = (coord2.latitude - coord1.latitude) * (M_PI/180);
    double lonDiff = (coord2.longitude - coord1.longitude) * (M_PI/180);
    double lat1InRadians = coord1.latitude * (M_PI/180);
    double lat2InRadians = coord2.latitude * (M_PI/180);
    double nA = pow ( sin(latDiff/2), 2 ) + cos(lat1InRadians) * cos(lat2InRadians) * pow ( sin(lonDiff/2), 2 );
    double nC = 2 * atan2( sqrt(nA), sqrt( 1 - nA ));
    double nD = nRadius * nC;
    // convert to meters
    return @(nD*1000);
}

Hope this helps!

Answer 3

To get distance from array of points in Swift use below reduce method.

Here locations is array of type CLLocation.

 let calculatedDistance = locations.reduce((0, locations[0])) { ($0.0 + $0.1.distance(from: $1), $1)}.0