geod_inv.c
1.51 KB
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
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
#ifndef lint
static const char SCCSID[]="@(#)geod_inv.c 4.5 95/09/23 GIE REL";
#endif
# include "projects.h"
# include "geodesic.h"
# define DTOL 1e-12
void
geod_inv(void) {
double th1,th2,thm,dthm,dlamm,dlam,sindlamm,costhm,sinthm,cosdthm,
sindthm,L,E,cosd,d,X,Y,T,sind,tandlammp,u,v,D,A,B;
if (ellipse) {
th1 = atan(onef * tan(phi1));
th2 = atan(onef * tan(phi2));
} else {
th1 = phi1;
th2 = phi2;
}
thm = .5 * (th1 + th2);
dthm = .5 * (th2 - th1);
dlamm = .5 * ( dlam = adjlon(lam2 - lam1) );
if (fabs(dlam) < DTOL && fabs(dthm) < DTOL) {
al12 = al21 = geod_S = 0.;
return;
}
sindlamm = sin(dlamm);
costhm = cos(thm); sinthm = sin(thm);
cosdthm = cos(dthm); sindthm = sin(dthm);
L = sindthm * sindthm + (cosdthm * cosdthm - sinthm * sinthm)
* sindlamm * sindlamm;
d = acos(cosd = 1 - L - L);
if (ellipse) {
E = cosd + cosd;
sind = sin( d );
Y = sinthm * cosdthm;
Y *= (Y + Y) / (1. - L);
T = sindthm * costhm;
T *= (T + T) / L;
X = Y + T;
Y -= T;
T = d / sind;
D = 4. * T * T;
A = D * E;
B = D + D;
geod_S = geod_a * sind * (T - f4 * (T * X - Y) +
f64 * (X * (A + (T - .5 * (A - E)) * X) -
Y * (B + E * Y) + D * X * Y));
tandlammp = tan(.5 * (dlam - .25 * (Y + Y - E * (4. - X)) *
(f2 * T + f64 * (32. * T - (20. * T - A)
* X - (B + 4.) * Y)) * tan(dlam)));
} else {
geod_S = geod_a * d;
tandlammp = tan(dlamm);
}
u = atan2(sindthm , (tandlammp * costhm));
v = atan2(cosdthm , (tandlammp * sinthm));
al12 = adjlon(TWOPI + v - u);
al21 = adjlon(TWOPI - v - u);
}