修正的经纬度球面面积计算

//算法依据：球面多边形计算面积的关键在于计算多边形所有角的度数.
        //对于球面n边形,所有角的和为S,球的半径为R,那么其面积就是
        //R^2*(S-(n-2)*Pi)
        function calcArea(PointX,PointY) 
        {
            var Count = PointX.length
            if (Count>3) 
            {
                var mtotalArea = 0;
                if((PointX[0]!=PointX[Count-1])||(PointY[0]!=PointY[Count-1]))
                {
                    return;
                }
                //一个顶角的三个点
                var LowX=0.0;
                var LowY=0.0;
                var MiddleX=0.0;
                var MiddleY=0.0;            
                var HighX=0.0;
                var HighY=0.0;

                var AM = 0.0;        
                var BM = 0.0;   
                var CM = 0.0;            

                var AL = 0.0;        
                var BL = 0.0;   
                var CL = 0.0;        
       
                var AH = 0.0;