distance function

double distance(double lat1, double lon1, double lat2, double lon2,)

Distance between two locations calculated with Haversine formula.

Implementation

double distance(double lat1, double lon1, double lat2, double lon2) {
  double dLat = _toRadians(lat2 - lat1);
  double dLon = _toRadians(lon2 - lon1);
  lat1 = _toRadians(lat1);
  lat2 = _toRadians(lat2);
  double a =
      pow(sin(dLat / 2), 2) + pow(sin(dLon / 2), 2) * cos(lat1) * cos(lat2);
  double c = 2 * asin(sqrt(a));
  return R * c;
}