/// <summary> /// Initializes the transform using the parameters from the specified coordinate system information /// </summary> /// <param name="projInfo">A ProjectionInfo class contains all the standard and custom parameters needed to initialize this transform</param> protected override void OnInit(ProjectionInfo projInfo) { if (Es != 0) { _en = MeridionalDistance.GetEn(Es); if (_en == null) { throw new ProjectionException(0); } _ml0 = MeridionalDistance.MeridionalLength(Phi0, Math.Sin(Phi0), Math.Cos(Phi0), _en); _esp = Es / (1 - Es); } else { _esp = K0; _ml0 = .5 * _esp; } }
/// <summary> /// The forward transform where the spheroidal model of the earth has a flattening factor, /// matching more closely with the oblique spheroid of the actual earth /// </summary> /// <param name="lp">The double values for geodetic lambda and phi organized into a one dimensional array</param> /// <param name="xy">The double values for linear x and y organized into a one dimensional array</param> /// <param name="startIndex">The zero based integer start index</param> /// <param name="numPoints">The integer count of the number of xy pairs in the lp and xy arrays</param> protected override void EllipticalForward(double[] lp, double[] xy, int startIndex, int numPoints) { for (int i = startIndex; i < startIndex + numPoints; i++) { int phi = i * 2 + PHI; int lam = i * 2 + LAMBDA; int x = i * 2 + X; int y = i * 2 + Y; /* * Fail if our longitude is more than 90 degrees from the * central meridian since the results are essentially garbage. * Is error -20 really an appropriate return value? * * http://trac.osgeo.org/proj/ticket/5 */ if (lp[lam] < -HALF_PI || lp[lam] > HALF_PI) { xy[x] = double.NaN; xy[y] = double.NaN; continue; //ProjectionException(14); } double sinphi = Math.Sin(lp[phi]); double cosphi = Math.Cos(lp[phi]); double t = Math.Abs(cosphi) > 1E-10 ? sinphi / cosphi : 0; t *= t; double al = cosphi * lp[lam]; double als = al * al; al /= Math.Sqrt(1 - Es * sinphi * sinphi); double n = _esp * cosphi * cosphi; xy[x] = K0 * al * (FC1 + FC3 * als * (1 - t + n + FC5 * als * (5 + t * (t - 18) + n * (14 - 58 * t) + FC7 * als * (61 + t * (t * (179 - t) - 479))))); xy[y] = K0 * (MeridionalDistance.MeridionalLength(lp[phi], sinphi, cosphi, _en) - _ml0 + sinphi * al * lp[lam] * FC2 * (1 + FC4 * als * (5 - t + n * (9 + 4 * n) + FC6 * als * (61 + t * (t - 58) + n * (270 - 330 * t) + FC8 * als * (1385 + t * (t * (543 - t) - 3111)))))); } }
/// <summary> /// Meridonal length function /// </summary> /// <param name="phi"></param> /// <param name="sphi"></param> /// <param name="cphi"></param> /// <param name="en"></param> /// <returns></returns> public static double Mlfn(double phi, double sphi, double cphi, double[] en) { return(MeridionalDistance.MeridionalLength(phi, sphi, cphi, en)); }