src/PJ_august.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

#define PJ_LIB__
#include	"projects.h"


PROJ_HEAD(august, "August Epicycloidal") "\n\tMisc Sph, no inv.";
#define M 1.333333333333333


static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
    XY xy = {0.0,0.0};
	double t, c1, c, x1, x12, y1, y12;
	(void) P;

	t = tan(.5 * lp.phi);
	c1 = sqrt(1. - t * t);
	c = 1. + c1 * cos(lp.lam *= .5);
	x1 = sin(lp.lam) *  c1 / c;
	y1 =  t / c;
	xy.x = M * x1 * (3. + (x12 = x1 * x1) - 3. * (y12 = y1 *  y1));
	xy.y = M * y1 * (3. + 3. * x12 - y12);
	return (xy);
}


PJ *PROJECTION(august) {
    P->inv = 0;
    P->fwd = s_forward;
    P->es = 0.;
    return P;
}