1 #include <u.h>
2 #include <libc.h>
3 #include "map.h"
4 
5 /* Given two lat-lon pairs, find an orientation for the
6    -o option of "map" that will place those two points
7    on the equator of a standard projection, equally spaced
8    about the prime meridian.
9 
10    -w and -l options are suggested also.
11 
12    Option -t prints out a series of
13    coordinates that follows the (great circle) track
14    in the original coordinate system,
15    followed by ".
16    This data is just right for map -t.
17 
18    Option -i inverts the map top-to-bottom.
19 */
20 struct place pole;
21 struct coord twist;
22 int track;
23 int inv = -1;
24 
25 extern void doroute(double, double, double, double, double);
26 
27 void
28 dorot(double a, double b, double *x, double *y, void (*f)(struct place *))
29 {
30 	struct place g;
31 	deg2rad(a,&g.nlat);
32 	deg2rad(b,&g.wlon);
33 	(*f)(&g);
34 	*x = g.nlat.l/RAD;
35 	*y = g.wlon.l/RAD;
36 }
37 
38 void
39 rotate(double a, double b, double *x, double *y)
40 {
41 	dorot(a,b,x,y,normalize);
42 }
43 
44 void
45 rinvert(double a, double b, double *x, double *y)
46 {
47 	dorot(a,b,x,y,invert);
48 }
49 
50 main(int argc, char **argv)
51 {
52 #pragma ref argv
53 	double an,aw,bn,bw;
54 	ARGBEGIN {
55 	case 't':
56 		track = 1;
57 		break;
58 
59 	case 'i':
60 		inv = 1;
61 		break;
62 
63 	default:
64 		exits("route: bad option");
65 	} ARGEND;
66 	if (argc<4) {
67 		print("use route [-t] [-i] lat lon lat lon\n");
68 		exits("arg count");
69 	}
70 	an = atof(argv[0]);
71 	aw = atof(argv[1]);
72 	bn = atof(argv[2]);
73 	bw = atof(argv[3]);
74 	doroute(inv*90.,an,aw,bn,bw);
75 	return 0;
76 }
77 
78 void
79 doroute(double dir, double an, double aw, double bn, double bw)
80 {
81 	double an1,aw1,bn1,bw1,pn,pw;
82 	double theta;
83 	double cn,cw,cn1,cw1;
84 	int i,n;
85 	orient(an,aw,0.);
86 	rotate(bn,bw,&bn1,&bw1);
87 /*	printf("b %f %f\n",bn1,bw1);*/
88 	orient(an,aw,bw1);
89 	rinvert(0.,dir,&pn,&pw);
90 /*	printf("p %f %f\n",pn,pw);*/
91 	orient(pn,pw,0.);
92 	rotate(an,aw,&an1,&aw1);
93 	rotate(bn,bw,&bn1,&bw1);
94 	theta = (aw1+bw1)/2;
95 /*	printf("a %f %f \n",an1,aw1);*/
96 	orient(pn,pw,theta);
97 	rotate(an,aw,&an1,&aw1);
98 	rotate(bn,bw,&bn1,&bw1);
99 	if(fabs(aw1-bw1)>180)
100 		if(theta<0.) theta+=180;
101 		else theta -= 180;
102 	orient(pn,pw,theta);
103 	rotate(an,aw,&an1,&aw1);
104 	rotate(bn,bw,&bn1,&bw1);
105 	if(!track) {
106 		double dlat, dlon, t;
107 		/* printf("A %.4f %.4f\n",an1,aw1); */
108 		/* printf("B %.4f %.4f\n",bn1,bw1); */
109 		cw1 = fabs(bw1-aw1);	/* angular difference for map margins */
110 		/* while (aw<0.0)
111 			aw += 360.;
112 		while (bw<0.0)
113 			bw += 360.; */
114 		dlon = fabs(aw-bw);
115 		if (dlon>180)
116 			dlon = 360-dlon;
117 		dlat = fabs(an-bn);
118 		printf("-o %.4f %.4f %.4f -w %.2f %.2f %.2f %.2f \n",
119 		  pn,pw,theta, -0.3*cw1, .3*cw1, -.6*cw1, .6*cw1);
120 
121 	} else {
122 		cn1 = 0;
123 		n = 1 + fabs(bw1-aw1)/.2;
124 		for(i=0;i<=n;i++) {
125 			cw1 = aw1 + i*(bw1-aw1)/n;
126 			rinvert(cn1,cw1,&cn,&cw);
127 			printf("%f %f\n",cn,cw);
128 		}
129 		printf("\"\n");
130 	}
131 }