https://blog.faceutil.com/2017/03/20/%ec%95%84%eb%91%90%ec%9d%b4%eb%85%b8-gps-%eb%aa%a8%eb%93%88%ec%9d%98-%ec%82%ac%ec%9a%a9-1%ed%8e%b8-gps-%eb%a1%9c%ea%b7%b8-%ec%b0%8d%ec%96%b4%eb%b3%b4%ea%b8%b0-%e3%83%85/