//高斯投影由经纬度(Unit:DD)计算大地平面坐标(含带号，Unit:Metres)
public static XYZCoordinate GaussProjCal(BLHCoordinate BLH, Datum datum, double lon)
{
int ProjNo, ZoneWide; ////带宽
double longitude0, X0, xval, yval;
double a, e2, ee, NN, T, C, A, M, b, l, h;
b = BLH.B;
l = BLH.L;
h = BLH.H;
ZoneWide = 3; //3度带宽
a = datum.r_major;
ProjNo = (int)((l - 1.5) / ZoneWide + 1);
longitude0 = lon;
if (Math.Abs(lon - 0) < 0.000001)
{
longitude0 = ProjNo * ZoneWide; //中央经线
}
longitude0 = longitude0 * Math.PI / 180;
l = l * Math.PI / 180; //经度转换为弧度
b = b * Math.PI / 180; //纬度转换为弧度
e2 = datum.E2;
ee = e2 * (1.0 - e2);
NN = a / Math.Sqrt(1.0 - e2 * Math.Sin(b) * Math.Sin(b));
T = Math.Tan(b) * Math.Tan(b);
C = ee * Math.Cos(b) * Math.Cos(b);
A = (l - longitude0) * Math.Cos(b);
M = a * ((1 - e2 / 4 - 3 * e2 * e2 / 64 - 5 * e2 * e2 * e2 / 256) * b - (3 * e2 / 8 + 3 * e2 * e2 / 32 + 45 * e2 * e2 * e2 / 1024) * Math.Sin(2 * b) + (15 * e2 * e2 / 256 + 45 * e2 * e2 * e2 / 1024) * Math.Sin(4 * b) - (35 * e2 * e2 * e2 / 3072) * Math.Sin(6 * b));
xval = NN * (A + (1 - T + C) * A * A * A / 6 + (5 - 18 * T + T * T + 72 * C - 58 * ee) * A * A * A * A * A / 120);
yval = M + NN * Math.Tan(b) * (A * A / 2 + (5 - T + 9 * C + 4 * C * C) * A * A * A * A / 24 + (61 - 58 * T + T * T + 600 * C - 330 * ee) * A * A * A * A * A * A / 720);
//X0 = 1000000L * ProjNo + 500000L;
X0 = 500000L;
xval = xval + X0;
return(new XYZCoordinate(xval, yval, h));
}
public static XYZCoordinate BLHToXYZ(BLHCoordinate BLH, Datum datum)
{
double a = datum.r_major;
double b = datum.r_minor;
double b1 = BLH.B * Pi / 180;
double l1 = BLH.L * Pi / 180;
double h1 = BLH.H;
double eq = datum.E2;
double N = a / Math.Sqrt(1 - eq * Math.Sin(b1) * Math.Sin(b1));
double Xq = (N + h1) * Math.Cos(b1) * Math.Cos(l1);
double Yq = (N + h1) * Math.Cos(b1) * Math.Sin(l1);
double Zq = ((1 - eq) * N + h1) * Math.Sin(b1);
return(new XYZCoordinate(Xq, Yq, Zq));
}
