좌표 최단거리 검색

두 좌표간의 직선 거리를 구하기 위한 함수이며, 지도 API 등에 활용하면 될 듯 하다.

사용해 본 결과 상당히 정확했음.

1) prototype 사용

 function calculateDistance(lat1, lon1, lat2, lon2) {
          var R = 6371; // km
          var dLat = (lat2-lat1).toRad();
          var dLon = (lon2-lon1).toRad(); 
          var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
                  Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) * 
                  Math.sin(dLon/2) * Math.sin(dLon/2); 
          var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
          var d = R * c;
          return d;
        } 
     
 
          Number.prototype.toRad = function() {
         return this * Math.PI / 180;
         
       } 

2) prototype 미사용

          function toRad(value){
             
             return value * Math.PI / 180;
             
         }
        
 
        function calculateDistance(lat1, lon1, lat2, lon2) {
              var R = 6371; // km
              var dLat = toRad(lat2-lat1);
              var dLon = toRad(lon2-lon1); 
              var a = Math.sin(dLat/2) * Math.sin(dLat/2) + Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLon/2) * Math.sin(dLon/2); 
              var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
              var d = R * c;
              return d;
            } 

출처 : https://stackoverflow.com/questions/5260423/torad-javascript-function-throwing-error/10459202

http://www.movable-type.co.uk/scripts/latlong.html