/// <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)
        {
            double pp;

            /* get control point locations */
            double phi1 = projInfo.GetPhi1();
            double lam1 = projInfo.GetLam1();
            double phi2 = projInfo.GetPhi2();
            double lam2 = projInfo.GetLam2();
            if (phi1 == phi2 && lam1 == lam2) throw new ProjectionException(-25);
            Lam0 = Proj.Adjlon(0.5*(lam1 + lam2));
            _dlam2 = Proj.Adjlon(lam2 - lam1);
            _cp1 = Math.Cos(phi1);
            _cp2 = Math.Cos(phi2);
            _sp1 = Math.Sin(phi1);
            _sp2 = Math.Sin(phi2);
            _cs = _cp1*_sp2;
            _sc = _sp1*_cp2;
            _ccs = _cp1*_cp2*Math.Sin(_dlam2);
            _z02 = Proj.Aacos(_sp1*_sp2 + _cp1*_cp2*Math.Cos(_dlam2));
            _hz0 = .5*_z02;
            double A12 = Math.Atan2(_cp2*Math.Sin(_dlam2),
                                    _cp1*_sp2 - _sp1*_cp2*Math.Cos(_dlam2));
            _ca = Math.Cos(pp = Proj.Aasin(_cp1*Math.Sin(A12)));
            _sa = Math.Sin(pp);
            _lp = Proj.Adjlon(Math.Atan2(_cp1*Math.Cos(A12), _sp1) - _hz0);
            _dlam2 *= .5;
            _lamc = HalfPi - Math.Atan2(Math.Sin(A12)*_sp1, Math.Cos(A12)) - _dlam2;
            _thz0 = Math.Tan(_hz0);
            _rhshz0 = .5/Math.Sin(_hz0);
            _r2z0 = 0.5/_z02;
            _z02 *= _z02;
        }
        /// <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)
        {
            double con;
            double f;
            double d;
            double toRadians = projInfo.GeographicInfo.Unit.Radians;
            _rot = projInfo.ParamI("no_rot") == 0;
            bool azi = projInfo.ParamD("alpha") != 0.0;
            if (azi)
            {
                _lamc = projInfo.ParamD("lonc")*toRadians;
                _alpha = projInfo.ParamD("alpha") *toRadians;
                if (Math.Abs(_alpha) < Tol ||
                    Math.Abs(Math.Abs(Phi0) - HalfPi) <= Tol ||
                    Math.Abs(Math.Abs(_alpha) - HalfPi) <= Tol)
                    throw new ProjectionException(32);
            }
            else
            {
                _lam1 = projInfo.GetLam1();
                _phi1 = projInfo.GetPhi1();
                _lam2 = projInfo.GetLam2();
                _phi2 = projInfo.GetPhi2();
                if(Math.Abs(_phi1 - _phi2) <= Tol ||
                    (con = Math.Abs(_phi1)) <= Tol ||
                    Math.Abs(con - HalfPi) <= Tol ||
                    Math.Abs(Math.Abs(Phi0) - HalfPi) <= Tol ||
                    Math.Abs(Math.Abs(_phi2) - HalfPi) <= Tol)
                {
                    throw new ProjectionException(33);
                }
            }
            _ellips = Es > 0;
            double com = _ellips ? Math.Sqrt(OneEs) : 1;
            if (Math.Abs(Phi0) > EPS10)
            {
                double sinph0 = Math.Sin(Phi0);
                double cosph0 = Math.Cos(Phi0);
                if (_ellips)
                {
                    con = 1 - Es*sinph0*sinph0;
                    _bl = cosph0*cosph0;
                    _bl = Math.Sqrt(1 + Es*_bl*_bl/OneEs);
                    _al = _bl*K0*com/con;
                    d = _bl*com/(cosph0*Math.Sqrt(con));
                }
                else
                {
                    _bl = 1;
                    _al = K0;
                    d = 1/cosph0;
                }


                if ((f = d*d - 1) <= 0)
                {
                    f = 0;
                }
                else
                {
                    f = Math.Sqrt(f);
                    if (Phi0 < 0) f = -f;
                }
                _el = f += d;
                if (_ellips)
                {
                    _el *= Math.Pow(Proj.Tsfn(Phi0, sinph0, E), _bl);
                }
                else
                {
                    _el *= TSFN0(Phi0);
                }
            }
            else
            {
                _bl = 1/com;
                _al = K0;
                _el = d = f = 1;
            }
            if(azi)
            {
                _gamma = Math.Asin(Math.Sin(_alpha)/d);
                Lam0 = _lamc - Math.Asin((.5*(f - 1/f))*Math.Tan(_gamma))/_bl;
            }
            else
            {
                double h;
                double l;
                if(_ellips)
                {
                    h = Math.Pow(Proj.Tsfn(_phi1, Math.Sin(_phi1), E), _bl);
                    l = Math.Pow(Proj.Tsfn(_phi2, Math.Sin(_phi2), E), _bl);
                }
                else
                {
                    h = TSFN0(_phi1);
                    l = TSFN0(_phi2);
                }
                f = _el/h;
                double p = (l - h)/(l + h);
                double j = _el*_el;
                j = (j - l*h)/(j + l*h);
                if ((con = _lam1 - _lam2) < -Math.PI)
                {
                    _lam2 -= Math.PI*2;
                }
                else if (con > Math.PI)
                {
                    _lam2 += Math.PI*2;
                }
                Lam0 = Proj.Adjlon(.5*(_lam1 + _lam2) - Math.Atan(j*Math.Tan(.5*_bl*(_lam1 - _lam2))/p)/_bl);
                _gamma = Math.Atan(2*Math.Sin(_bl*Proj.Adjlon(_lam1 - Lam0))/(f - 1/f));
                _alpha = Math.Asin(d*Math.Sin(_gamma));
            }
            _singam = Math.Sin(_gamma);
            _cosgam = Math.Cos(_gamma);
            if(projInfo.ParamI("rot_conv") != 0)
            {
                f = _gamma;
            }
            else
            {
                f = _alpha;
            }
            _sinrot = Math.Sin(f);
            _cosrot = Math.Cos(f);
            if(projInfo.ParamI("no_uoff") != 0)
            {
                _u0 = 0;
            }
            else
            {
                _u0 = Math.Abs(_al*Math.Atan(Math.Sqrt(d*d - 1)/_cosrot)/_bl);
               
            }
            if (Phi0 < 0) _u0 = -_u0;
        }