GPS经纬度换算成XY坐标

         ///<summary>
        /// GPS经纬度换算成x,y坐标
        ///</summary>
        ///<param name="l">精度</param>
        ///<param name="B">纬度</param>
        ///<param name="xc">X坐标</param>
        ///<param name="yc">Y坐标</param>
        publicstaticvoid MCT84Bl2xy(double l, double B, outdouble xc, outdouble yc)
        {
            try
            {
l = l * Math.PI /180;
                B = B * Math.PI /180;

                double B0 =30* Math.PI /180;

                double N =0, e =0, a =0, b =0, e2 =0, K =0;
                a =6378137;
                b =6356752.3142;
                e = Math.Sqrt(1- (b / a) * (b / a));
e2 = Math.Sqrt((a / b) * (a / b) -1);
                double CosB0 = Math.Cos(B0);
                N = (a * a / b) / Math.Sqrt(1+ e2 * e2 * CosB0 * CosB0);
                K = N * CosB0;

                double Pi = Math.PI;
                double SinB = Math.Sin(B);

                double tan = Math.Tan(Pi /4+ B /2);
                double E2 = Math.Pow((1- e * SinB) / (1+ e * SinB), e /2);
                double xx = tan * E2;

                xc = K * Math.Log(xx);
                yc = K * l;
                return;
            }
            catch (Exception ErrInfo)
            {
            }
            xc =-1;
            yc =-1;
        }