PJ_hatano.c

#define PJ_LIB__
#include	<projects.h>
PROJ_HEAD(hatano, "Hatano Asymmetrical Equal Area") "\n\tPCyl, Sph.";
#define NITER	20
#define EPS	1e-7
#define ONETOL 1.000001
#define CN	2.67595
#define CS	2.43763
#define RCN	0.37369906014686373063
#define RCS	0.41023453108141924738
#define FYCN	1.75859
#define FYCS	1.93052
#define RYCN	0.56863737426006061674
#define RYCS	0.51799515156538134803
#define FXC	0.85
#define RXC	1.17647058823529411764
FORWARD(s_forward); /* spheroid */
	double th1, c;
	int i;
	(void) P;

	c = sin(lp.phi) * (lp.phi < 0. ? CS : CN);
	for (i = NITER; i; --i) {
		lp.phi -= th1 = (lp.phi + sin(lp.phi) - c) / (1. + cos(lp.phi));
		if (fabs(th1) < EPS) break;
	}
	xy.x = FXC * lp.lam * cos(lp.phi *= .5);
	xy.y = sin(lp.phi) * (lp.phi < 0. ? FYCS : FYCN);
	return (xy);
}
INVERSE(s_inverse); /* spheroid */
	double th;

	th = xy.y * ( xy.y < 0. ? RYCS : RYCN);
	if (fabs(th) > 1.)
		if (fabs(th) > ONETOL)	I_ERROR
		else			th = th > 0. ? HALFPI : - HALFPI;
	else
		th = asin(th);
	lp.lam = RXC * xy.x / cos(th);
	th += th;
	lp.phi = (th + sin(th)) * (xy.y < 0. ? RCS : RCN);
	if (fabs(lp.phi) > 1.)
		if (fabs(lp.phi) > ONETOL)	I_ERROR
		else			lp.phi = lp.phi > 0. ? HALFPI : - HALFPI;
	else
		lp.phi = asin(lp.phi);
	return (lp);
}
FREEUP; if (P) pj_dalloc(P); }
ENTRY0(hatano) P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P)