Calculate a new coordinate given a starting coordinate, bearing and distance. Objective-C

AnnotationCoordinateUtility.m

#import <CoreLocation/CoreLocation.h>
#import <MapKit/MapKit.h>
#import "AnnotationCoordinateUtility.h"


@implementation AnnotationCoordinateUtility {
    }

    + (void)mutateCoordinatesOfClashingAnnotations:(NSArray *)annotations {

        NSDictionary *coordinateValuesToAnnotations = [self groupAnnotationsByLocationValue:annotations];

        for (NSValue *coordinateValue in coordinateValuesToAnnotations.allKeys) {
            NSMutableArray *outletsAtLocation = coordinateValuesToAnnotations[coordinateValue];
            if (outletsAtLocation.count > 1) {
                CLLocationCoordinate2D coordinate;
                [coordinateValue getValue:&coordinate];
                [self repositionAnnotations:outletsAtLocation toAvoidClashAtCoordination:coordinate];
            }
        }
    }

    + (NSDictionary *)groupAnnotationsByLocationValue:(NSArray *)annotations {

        NSMutableDictionary *result = [NSMutableDictionary dictionary];

        for (id<MKAnnotation> pin in annotations) {

            CLLocationCoordinate2D coordinate = pin.coordinate;
            NSValue *coordinateValue = [NSValue valueWithBytes:&coordinate objCType:@encode(CLLocationCoordinate2D)];

            NSMutableArray *annotationsAtLocation = result[coordinateValue];
            if (!annotationsAtLocation) {
                annotationsAtLocation = [NSMutableArray array];
                result[coordinateValue] = annotationsAtLocation;
            }

            [annotationsAtLocation addObject:pin];
        }
        return result;
    }

    + (void)repositionAnnotations:(NSMutableArray *)annotations toAvoidClashAtCoordination:(CLLocationCoordinate2D)coordinate {

        double distance = 3 * annotations.count / 2.0;
        double radiansBetweenAnnotations = (M_PI * 2) / annotations.count;

        for (int i = 0; i < annotations.count; i++) {

            double heading = radiansBetweenAnnotations * i;
            CLLocationCoordinate2D newCoordinate = [self calculateCoordinateFrom:coordinate onBearing:heading atDistance:distance];

            id <MKAnnotation> annotation = annotations[i];
            annotation.coordinate = newCoordinate;
        }
    }

    + (CLLocationCoordinate2D)calculateCoordinateFrom:(CLLocationCoordinate2D)coordinate  onBearing:(double)bearingInRadians atDistance:(double)distanceInMetres {

        double coordinateLatitudeInRadians = coordinate.latitude * M_PI / 180;
        double coordinateLongitudeInRadians = coordinate.longitude * M_PI / 180;

        double distanceComparedToEarth = distanceInMetres / 6378100;

        double resultLatitudeInRadians = asin(sin(coordinateLatitudeInRadians) * cos(distanceComparedToEarth) + cos(coordinateLatitudeInRadians) * sin(distanceComparedToEarth) * cos(bearingInRadians));
        double resultLongitudeInRadians = coordinateLongitudeInRadians + atan2(sin(bearingInRadians) * sin(distanceComparedToEarth) * cos(coordinateLatitudeInRadians), cos(distanceComparedToEarth) - sin(coordinateLatitudeInRadians) * sin(resultLatitudeInRadians));

        CLLocationCoordinate2D result;
        result.latitude = resultLatitudeInRadians * 180 / M_PI;
        result.longitude = resultLongitudeInRadians * 180 / M_PI;
        return result;
    }

@end