1 #include <u.h>
2 #include <libc.h>
3 #include "map.h"
4 
5 static struct place gywhem, gyehem;
6 static struct coord gytwist;
7 static double gyconst, gykc, gyside;
8 
9 
10 static void
11 dosquare(double z1, double z2, double *x, double *y)
12 {
13 	double w1,w2;
14 	w1 = z1 -1;
15 	if(fabs(w1*w1+z2*z2)>.000001) {
16 		cdiv(z1+1,z2,w1,z2,&w1,&w2);
17 		w1 *= gyconst;
18 		w2 *= gyconst;
19 		if(w1<0)
20 			w1 = 0;
21 		elco2(w1,w2,gykc,1.,1.,x,y);
22 	} else {
23 		*x = gyside;
24 		*y = 0;
25 	}
26 }
27 
28 int
29 Xguyou(struct place *place, double *x, double *y)
30 {
31 	int ew;		/*which hemisphere*/
32 	double z1,z2;
33 	struct place pl;
34 	ew = place->wlon.l<0;
35 	copyplace(place,&pl);
36 	norm(&pl,ew?&gyehem:&gywhem,&gytwist);
37 	Xstereographic(&pl,&z1,&z2);
38 	dosquare(z1/2,z2/2,x,y);
39 	if(!ew)
40 		*x -= gyside;
41 	return(1);
42 }
43 
44 proj
45 guyou(void)
46 {
47 	double junk;
48 	gykc = 1/(3+2*sqrt(2.));
49 	gyconst = -(1+sqrt(2.));
50 	elco2(-gyconst,0.,gykc,1.,1.,&gyside,&junk);
51 	gyside *= 2;
52 	latlon(0.,90.,&gywhem);
53 	latlon(0.,-90.,&gyehem);
54 	deg2rad(0.,&gytwist);
55 	return(Xguyou);
56 }
57 
58 int
59 guycut(struct place *g, struct place *og, double *cutlon)
60 {
61 	int c;
62 	c = picut(g,og,cutlon);
63 	if(c!=1)
64 		return(c);
65 	*cutlon = 0.;
66 	if(g->nlat.c<.7071||og->nlat.c<.7071)
67 		return(ckcut(g,og,0.));
68 	return(1);
69 }
70 
71 static int
72 Xsquare(struct place *place, double *x, double *y)
73 {
74 	double z1,z2;
75 	double r, theta;
76 	struct place p;
77 	copyplace(place,&p);
78 	if(place->nlat.l<0) {
79 		p.nlat.l = -p.nlat.l;
80 		p.nlat.s = -p.nlat.s;
81 	}
82 	if(p.nlat.l<FUZZ && fabs(p.wlon.l)>PI-FUZZ){
83 		*y = -gyside/2;
84 		*x = p.wlon.l>0?0:gyside;
85 		return(1);
86 	}
87 	Xstereographic(&p,&z1,&z2);
88 	r = sqrt(sqrt(hypot(z1,z2)/2));
89 	theta = atan2(z1,-z2)/4;
90 	dosquare(r*sin(theta),-r*cos(theta),x,y);
91 	if(place->nlat.l<0)
92 		*y = -gyside - *y;
93 	return(1);
94 }
95 
96 proj
97 square(void)
98 {
99 	guyou();
100 	return(Xsquare);
101 }