blob: fe17eaa6b86e5e01148eb39045912e4e6cab1762 (
plain)
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
34
35
36
37
38
39
40
41
42
43
44
|
#define PJ_LIB__
# include <errno.h>
# include <projects.h>
PROJ_HEAD(boggs, "Boggs Eumorphic") "\n\tPCyl., no inv., Sph.";
# define NITER 20
# define EPS 1e-7
# define ONETOL 1.000001
# define FXC 2.00276
# define FXC2 1.11072
# define FYC 0.49931
static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */
XY xy = {0.0,0.0};
double theta, th1, c;
int i;
(void) P;
theta = lp.phi;
if (fabs(fabs(lp.phi) - M_HALFPI) < EPS)
xy.x = 0.;
else {
c = sin(theta) * M_PI;
for (i = NITER; i; --i) {
theta -= th1 = (theta + sin(theta) - c) /
(1. + cos(theta));
if (fabs(th1) < EPS) break;
}
theta *= 0.5;
xy.x = FXC * lp.lam / (1. / cos(lp.phi) + FXC2 / cos(theta));
}
xy.y = FYC * (lp.phi + M_SQRT2 * sin(theta));
return (xy);
}
PJ *PROJECTION(boggs) {
P->es = 0.;
P->fwd = s_forward;
return P;
}
|
