haversineDistance static method
Returns the haversine distance in metres between a and b.
Implementation
static double haversineDistance(LatLng a, LatLng b) {
final dLat = _toRad(b.latitude - a.latitude);
final dLng = _toRad(b.longitude - a.longitude);
final sinDLat = sin(dLat / 2);
final sinDLng = sin(dLng / 2);
final x = sinDLat * sinDLat +
cos(_toRad(a.latitude)) * cos(_toRad(b.latitude)) * sinDLng * sinDLng;
return _earthRadius * 2 * atan2(sqrt(x), sqrt(1 - x));
}