/Proj4/PJ_hatano.c

 1#ifndef lint
 2static const char SCCSID[]="@(#)PJ_hatano.c	4.1 94/02/15     GIE     REL";
 3#endif
 4#define PJ_LIB__
 5#include	"projects.h"
 6PROJ_HEAD(hatano, "Hatano Asymmetrical Equal Area") "\n\tPCyl, Sph.";
 7#define NITER	20
 8#define EPS	1e-7
 9#define ONETOL 1.000001
10#define CN	2.67595
11#define CS	2.43763
12#define RCN	0.37369906014686373063
13#define RCS	0.41023453108141924738
14#define FYCN	1.75859
15#define FYCS	1.93052
16#define RYCN	0.56863737426006061674
17#define RYCS	0.51799515156538134803
18#define FXC	0.85
19#define RXC	1.17647058823529411764
20FORWARD(s_forward); /* spheroid */
21	double th1, c;
22	int i;
23
24	c = sin(lp.phi) * (lp.phi < 0. ? CS : CN);
25	for (i = NITER; i; --i) {
26		lp.phi -= th1 = (lp.phi + sin(lp.phi) - c) / (1. + cos(lp.phi));
27		if (fabs(th1) < EPS) break;
28	}
29	xy.x = FXC * lp.lam * cos(lp.phi *= .5);
30	xy.y = sin(lp.phi) * (lp.phi < 0. ? FYCS : FYCN);
31	return (xy);
32}
33INVERSE(s_inverse); /* spheroid */
34	double th;
35
36	th = xy.y * ( xy.y < 0. ? RYCS : RYCN);
37	if (fabs(th) > 1.)
38		if (fabs(th) > ONETOL)	I_ERROR
39		else			th = th > 0. ? HALFPI : - HALFPI;
40	else
41		th = asin(th);
42	lp.lam = RXC * xy.x / cos(th);
43	th += th;
44	lp.phi = (th + sin(th)) * (xy.y < 0. ? RCS : RCN);
45	if (fabs(lp.phi) > 1.)
46		if (fabs(lp.phi) > ONETOL)	I_ERROR
47		else			lp.phi = lp.phi > 0. ? HALFPI : - HALFPI;
48	else
49		lp.phi = asin(lp.phi);
50	return (lp);
51}
52FREEUP; if (P) pj_dalloc(P); }
53ENTRY0(hatano) P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; ENDENTRY(P)