따라한곳은 http://avionics.tistory.com/tag/%EA%B1%B0%EB%A6%AC%EA%B5%AC%ED%95%98%EA%B8%B0 
인데요

public double  LOCATION_TO_LOCATION_LENGTH(Location A, double B_LATITUDE , double B_LONGITUDE){
  double A_TO_B_LENGTH = 0;
  double A_LATITUDE = A.getLatitude()*1E6;
  double A_LONGITUDE = A.getLongitude()*1E6;
  
  
  
  if((A_LATITUDE == B_LATITUDE)&& (A_LONGITUDE == B_LONGITUDE)){
   A_TO_B_LENGTH = 0;
   return A_TO_B_LENGTH;
  }else{
   if(Math.sin(A_LATITUDE) * Math.sin(B_LATITUDE) + (Math.cos(A_LATITUDE)*Math.cos(B_LATITUDE)*Math.cos(A_LONGITUDE-B_LONGITUDE)) >1 ){
    A_TO_B_LENGTH = 3963.1 * Math.acos(1);
    return A_TO_B_LENGTH;
   }else{
    return 3963.1 * Math.acos((Math.sin(A_LATITUDE)*Math.sin(B_LATITUDE))+(Math.cos(A_LATITUDE)*Math.cos(B_LATITUDE)*Math.cos(A_LONGITUDE-B_LONGITUDE)));
   }
  }
 }


인데 결과가 좀..... 단위는 마일로 계산해주는거 같아요 ,,,
제대로 되는걸까요 ?