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static const char SCCSID[]="@(#)PJ_poly.c 4.1 94/02/15 GIE REL";
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PROJ_HEAD(poly, "Polyconic (American)")
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FORWARD(e_forward); /* ellipsoid */
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if (fabs(lp.phi) <= TOL) { xy.x = lp.lam; xy.y = -P->ml0; }
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ms = fabs(cp = cos(lp.phi)) > TOL ? pj_msfn(sp, cp, P->es) / sp : 0.;
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xy.x = ms * sin(lp.lam *= sp);
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xy.y = (pj_mlfn(lp.phi, sp, cp, P->en) - P->ml0) + ms * (1. - cos(lp.lam));
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FORWARD(s_forward); /* spheroid */
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if (fabs(lp.phi) <= TOL) { xy.x = lp.lam; xy.y = P->ml0; }
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cot = 1. / tan(lp.phi);
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xy.x = sin(E = lp.lam * sin(lp.phi)) * cot;
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xy.y = lp.phi - P->phi0 + cot * (1. - cos(E));
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INVERSE(e_inverse); /* ellipsoid */
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if (fabs(xy.y) <= TOL) { lp.lam = xy.x; lp.phi = 0.; }
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double r, c, sp, cp, s2ph, ml, mlb, mlp, dPhi;
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r = xy.y * xy.y + xy.x * xy.x;
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for (lp.phi = xy.y, i = I_ITER; i ; --i) {
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s2ph = sp * ( cp = cos(lp.phi));
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c = sp * (mlp = sqrt(1. - P->es * sp * sp)) / cp;
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ml = pj_mlfn(lp.phi, sp, cp, P->en);
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mlp = P->one_es / (mlp * mlp * mlp);
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( ml + ml + c * mlb - 2. * xy.y * (c * ml + 1.) ) / (
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P->es * s2ph * (mlb - 2. * xy.y * ml) / c +
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2.* (xy.y - ml) * (c * mlp - 1. / s2ph) - mlp - mlp ));
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if (fabs(dPhi) <= ITOL)
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lp.lam = asin(xy.x * tan(lp.phi) * sqrt(1. - P->es * c * c)) / sin(lp.phi);
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INVERSE(s_inverse); /* spheroid */
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if (fabs(xy.y = P->phi0 + xy.y) <= TOL) { lp.lam = xy.x; lp.phi = 0.; }
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B = xy.x * xy.x + xy.y * xy.y;
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lp.phi -= (dphi = (xy.y * (lp.phi * tp + 1.) - lp.phi -
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.5 * ( lp.phi * lp.phi + B) * tp) /
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((lp.phi - xy.y) / tp - 1.));
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} while (fabs(dphi) > CONV && --i);
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lp.lam = asin(xy.x * tan(lp.phi)) / sin(lp.phi);
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FREEUP; if (P) { if (P->en) pj_dalloc(P->en); pj_dalloc(P); } }
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if (!(P->en = pj_enfn(P->es))) E_ERROR_0;
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P->ml0 = pj_mlfn(P->phi0, sin(P->phi0), cos(P->phi0), P->en);