GeoDistance between two points using lat/long, per http://stackoverflow.com/questions/2010466/how-can-i-determine-the-distance-between-two-sets-of-lattitude-longitude-coordin

geodistance.m

double ToRadians(double degrees) { return degrees * M_PI / 180; }

- (NSNumber *)geoDistanceFromLat:(CLLocationDegrees)lat1 fromLon:(CLLocationDegrees)lng1 toLat:(CLLocationDegrees)lat2 toLon:(CLLocationDegrees)lng2 {
	
	CLLocationDistance EarthRadiusInMeters = 6367000.0;
	
	CLLocationDistance distance = EarthRadiusInMeters * 2 *
	asin(fmin(1, sqrt((pow(sin((ToRadians(lat2) - ToRadians(lat1)) / 2.0),2.0)
						+
					   cos(ToRadians(lat1)) * cos(ToRadians(lat2))
						*
					   pow(sin((ToRadians(lng2) - ToRadians(lng1)) / 2.0), 2.0)
					   )
					  )
			  )
		 );
	
	return @(distance);
}