How to show heading direction from Current location to other location on map in ios?

Question

I have a requirement where i have to show the heading direction towards any location on map from user current location. Let say if we have 4 location annotation on map apart from current location and i want to show heading towards any of the location after tapping on it. How can we achieve it. I have gone trough Map API documentation & Locaiotn API, I found that we get the heading value in the delegate method which provided by API when we called the startupdatingheading method. I not getting idea how can we externally get the heading data between two locations. Please help me out. Thanks in advance.

Answer 1

This will calculate the initial bearing to get from lat1,lon1 to lat2,lon2 on a straight line.

double lat1=48.0;  // source latitude, example data
double lon1=17.0;  // source longitude

double lat2=49.0;  // destination latitude
double lon2=18.0;  // destination longitude

double lat1Rad = lat1 * M_PI / 180;
double lat2Rad = lat2 * M_PI / 180;

double dLon = (lon2 - lon1) * M_PI / 180;

double y = sin(dLon) * cos(lat2Rad);
double x = cos(lat1Rad) * sin(lat2Rad) - sin(lat1Rad) * cos(lat2Rad) * cos(dLon);

double bearingRad = atan2(y, x);

// this is the bearing from source to destination in degrees, normalized to 0..360
double bearing = fmod((bearingRad * 180 / M_PI + 360),360);

Answer 2

Swift version:

func getHeading(fromLoc: CLLocationCoordinate2D, toLoc: CLLocationCoordinate2D) -> Double {
    let lat1Rad = fromLoc.latitude * Double.pi / 180
    let lat2Rad = toLoc.latitude * Double.pi / 180
    let dLon = (toLoc.longitude - fromLoc.longitude) * Double.pi / 180
    let y = sin(dLon) * cos(lat2Rad)
    let x = cos(lat1Rad) * sin(lat2Rad) - sin(lat1Rad) * cos(lat2Rad) * cos(dLon)
    let bearingRad = atan2(y, x)
    // this is the bearing from/to in degrees, normalized to 0..360
    return fmod((bearingRad * 180 / Double.pi + 360),360);
}