Arduino get direction / bearing from two geolocations

gistfile1.ino

/*
 * Arduino geolocation bearing calculation based on two geolocation latitude-longitude values
 * Johannes 'kontur' Neumeier, 2015
 * https://gist.github.com/kontur/794b04537a9bea84c40c
 */

void setup() {
  Serial.begin(9600);
  Serial.println(getDirection(60.1650338, 24.8768908, 60.1243045, 26.2730065));
}

void loop() {
}


/*
reference java implementation

protected static double bearing(double lat1, double lon1, double lat2, double lon2){
  double longitude1 = lon1;
  double longitude2 = lon2;
  double latitude1 = Math.toRadians(lat1);
  double latitude2 = Math.toRadians(lat2);
  double longDiff= Math.toRadians(longitude2-longitude1);
  double y= Math.sin(longDiff)*Math.cos(latitude2);
  double x=Math.cos(latitude1)*Math.sin(latitude2)-Math.sin(latitude1)*Math.cos(latitude2)*Math.cos(longDiff);

  return (Math.toDegrees(Math.atan2(y, x))+360)%360;
}
*/

int getDirection(float latitude1, float longitude1, float latitude2, float longitude2) {
  float lat1 = toRadians(latitude1);
  float lat2 = toRadians(latitude2);
  float lng1 = toRadians(longitude1);
  float lng2 = toRadians(longitude2);
  float Y = sin(lng2 - lng1) * cos(lat2);
  float X = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(lng2 - lng1);  
  float deg = toDegrees(atan2(Y, X));  
  // note that this implementation doesn't use the module, but angles lower than 0 get augmented by 360 only
  if (deg < 0) {
    deg = 360 + deg;
  }
  float angle = deg;
  int a = (int) (abs(angle) + (1 / 7200));
  return a;
}

float toRadians(float angle) {
  return (PI / 180) * angle;
}

float toDegrees(float rad) {
  return (rad * 180) / PI;
}