北京54投影坐标系的cad坐标转84地理坐标系的算法

这里的是没有给定参数所以没有用七参法，先将投影坐标系转了地理坐标系，然后做了横纵和比例纠偏

        public static double[] Transform(PointF point)
        {
            double xParam = 94.362163134086399;
            double yParam = -310.26525523306055;

            double xMultiple = 1.19862910076924;
            double yMultiple = 1;

            //旋转中心点
            double centerX = 114.00092403;
            double centerY = 36.14333070;

            //旋转角度
            double Angle = 0.064894377180536;

            double X = Math.Round(point.X, 7) + 4000000;
            double Y = Math.Round(point.Y, 7) + 38500000;

            //double X = 60139 + 4000000;
            //double Y = 34944 + 38500000;

            // 由高斯投影坐标反算成经纬度
            int ProjNo; int ZoneWide; ////带宽
            double[] output = new double[2];
            double longitude1, latitude1, longitude0, X0, Y0, xval, yval;//latitude0,
            double e1, e2, f, a, ee, NN, T, C, M, D, R, u, fai, iPI;
            iPI = 0.0174532925199433; ////3.1415926535898/180.0;
            a = 6378245.0; f = 1.0 / 298.3; //54年北京坐标系参数
                                            //a = 6378140.0; f = 1 / 298.257; //80年西安坐标系参数
            ZoneWide = 6; ////6度带宽
            ProjNo = (int)(X / 1000000L); //查找带号
            longitude0 = (ProjNo - 1) * ZoneWide + ZoneWide / 2;
            longitude0 = longitude0 * iPI; //中央经线

            X0 = ProjNo * 1000000L + 500000L;
            Y0 = 0;
            xval = X - X0; yval = Y - Y0; //带内大地坐标
            e2 = 2 * f - f * f;
            e1 = (1.0 - Math.Sqrt(1 - e2)) / (1.0 + Math.Sqrt(1 - e2));
            ee = e2 / (1 - e2);
            M = yval;
            u = M / (a * (1 - e2 / 4 - 3 * e2 * e2 / 64 - 5 * e2 * e2 * e2 / 256));
            fai = u + (3 * e1 / 2 - 27 * e1 * e1 * e1 / 32) * Math.Sin(2 * u) + (21 * e1 * e1 / 16 - 55 * e1 * e1 * e1 * e1 / 32) * Math.Sin(4 * u)
            + (151 * e1 * e1 * e1 / 96) * Math.Sin(6 * u) + (1097 * e1 * e1 * e1 * e1 / 512) * Math.Sin(8 * u);
            C = ee * Math.Cos(fai) * Math.Cos(fai);
            T = Math.Tan(fai) * Math.Tan(fai);
            NN = a / Math.Sqrt(1.0 - e2 * Math.Sin(fai) * Math.Sin(fai));
            R = a * (1 - e2) / Math.Sqrt((1 - e2 * Math.Sin(fai) * Math.Sin(fai)) * (1 - e2 * Math.Sin(fai) * Math.Sin(fai)) * (1 - e2 * Math.Sin
            (fai) * Math.Sin(fai)));
            D = xval / NN;
            //计算经度(Longitude) 纬度(Latitude)
            longitude1 = longitude0 + (D - (1 + 2 * T + C) * D * D * D / 6 + (5 - 2 * C + 28 * T - 3 * C * C + 8 * ee + 24 * T * T) * D
            * D * D * D * D / 120) / Math.Cos(fai);
            latitude1 = fai - (NN * Math.Tan(fai) / R) * (D * D / 2 - (5 + 3 * T + 10 * C - 4 * C * C - 9 * ee) * D * D * D * D / 24
            + (61 + 90 * T + 298 * C + 45 * T * T - 256 * ee - 3 * C * C) * D * D * D * D * D * D / 720);
            // 现状图
            output[0] = longitude1 / iPI * xMultiple + xParam;
            output[1] = latitude1 / iPI * yMultiple + yParam;
            return output;
        }

横向有20m左右偏差，纵向有3m左右偏差。因为cad没有旋转，所以没有做旋转的纠偏。

这里的代码仅作参考，有更好建议可以提出来大家一起研究