Rough Haversine Formula

gistfile1.txt

#import "CLLocation+NHIAdditions.h"

@implementation CLLocation (NHIAdditions)

- (CGFloat)distanceToPoint:(CLLocation*)pointB
{
    //uses the haversine formula. http://en.wikipedia.org/wiki/Haversine_formula
    NSInteger nRadius = 6371; // Earth's radius in Kilometers
    // Get the difference between our two points then convert the difference into radians
    CGFloat differenceInLatitudes = (pointB.coordinate.latitude - self.coordinate.latitude) * (M_PI/180);
    CGFloat differenceInLongitudes = (pointB.coordinate.longitude - self.coordinate.longitude) * (M_PI/180);
    
    CGFloat pointALatitudeInRadians = degreesToRadian(self.coordinate.latitude);
    CGFloat pointBLatitudeInRadians = degreesToRadian(pointB.coordinate.latitude);
    
    CGFloat nA = pow ( sin(differenceInLatitudes/2), 2 ) + cos(pointALatitudeInRadians) * cos(pointBLatitudeInRadians) * pow ( sin(differenceInLongitudes/2), 2 );
    
    CGFloat nC = 2 * atan2( sqrt(nA), sqrt( 1 - nA ));
    CGFloat distance = nRadius * nC;
    
    return distance; // Return our calculated distance
}

@end