public double distanceInMetres(@NotNull LatLong other){
  double lngDelta=Math.abs(lng - other.lng);
  if (lngDelta > 180)   lngDelta=360 - lngDelta;
  double p1=lngDelta * Math.cos(0.5 * radians * (lat + other.lat));
  double p2=(lat - other.lat);
  return EarthRadius * radians * Math.sqrt(p1 * p1 + p2 * p2);
}

public double distanceInMetres ( @ NotNull LatLong other ) { double lngDelta = Math . abs ( lng - other . lng ) ; if ( lngDelta > 180 ) lngDelta = 360 - lngDelta ; double p1 = lngDelta * Math . cos ( 0.5 * radians * ( lat + other . lat ) ) ; double p2 = ( lat - other . lat ) ; return EarthRadius * radians * Math . sqrt ( p1 * p1 + p2 * p2 ) ; }
this is the equirectangular approximation . it ' s a little slower than the region . distanceinmetres ( ) formula .
