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Date:: Fri Apr 21 04:00:56 2006 UTC
Message:: system tan() is probably good enough
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  1 28994509 2004-04-21 devnull #include <u.h>
  2 28994509 2004-04-21 devnull #include <libc.h>
  3 28994509 2004-04-21 devnull #include <stdio.h>
  4 28994509 2004-04-21 devnull #include "map.h"
  5 28994509 2004-04-21 devnull 
  6 28994509 2004-04-21 devnull static double cirmod(double);
  7 28994509 2004-04-21 devnull 
  8 28994509 2004-04-21 devnull static struct place pole;	/* map pole is tilted to here */
  9 28994509 2004-04-21 devnull static struct coord twist;	/* then twisted this much */
 10 28994509 2004-04-21 devnull static struct place ipole;	/* inverse transfrom */
 11 28994509 2004-04-21 devnull static struct coord itwist;
 12 28994509 2004-04-21 devnull 
 13 28994509 2004-04-21 devnull void
 14 28994509 2004-04-21 devnull orient(double lat, double lon, double theta)
 15 28994509 2004-04-21 devnull {
 16 28994509 2004-04-21 devnull 	lat = cirmod(lat);
 17 28994509 2004-04-21 devnull 	if(lat>90.) {
 18 28994509 2004-04-21 devnull 		lat = 180. - lat;
 19 28994509 2004-04-21 devnull 		lon -= 180.;
 20 28994509 2004-04-21 devnull 		theta -= 180.;
 21 28994509 2004-04-21 devnull 	} else if(lat < -90.) {
 22 28994509 2004-04-21 devnull 		lat = -180. - lat;
 23 28994509 2004-04-21 devnull 		lon -= 180.;
 24 28994509 2004-04-21 devnull 		theta -= 180;
 25 28994509 2004-04-21 devnull 	}
 26 28994509 2004-04-21 devnull 	latlon(lat,lon,&pole);
 27 28994509 2004-04-21 devnull 	deg2rad(theta, &twist);
 28 28994509 2004-04-21 devnull 	latlon(lat,180.-theta,&ipole);
 29 28994509 2004-04-21 devnull 	deg2rad(180.-lon, &itwist);
 30 28994509 2004-04-21 devnull }
 31 28994509 2004-04-21 devnull 
 32 28994509 2004-04-21 devnull void
 33 28994509 2004-04-21 devnull latlon(double lat, double lon, struct place *p)
 34 28994509 2004-04-21 devnull {
 35 28994509 2004-04-21 devnull 	lat = cirmod(lat);
 36 28994509 2004-04-21 devnull 	if(lat>90.) {
 37 28994509 2004-04-21 devnull 		lat = 180. - lat;
 38 28994509 2004-04-21 devnull 		lon -= 180.;
 39 28994509 2004-04-21 devnull 	} else if(lat < -90.) {
 40 28994509 2004-04-21 devnull 		lat = -180. - lat;
 41 28994509 2004-04-21 devnull 		lon -= 180.;
 42 28994509 2004-04-21 devnull 	}
 43 28994509 2004-04-21 devnull 	deg2rad(lat,&p->nlat);
 44 28994509 2004-04-21 devnull 	deg2rad(lon,&p->wlon);
 45 28994509 2004-04-21 devnull }
 46 28994509 2004-04-21 devnull 
 47 28994509 2004-04-21 devnull void
 48 28994509 2004-04-21 devnull deg2rad(double theta, struct coord *coord)
 49 28994509 2004-04-21 devnull {
 50 28994509 2004-04-21 devnull 	theta = cirmod(theta);
 51 28994509 2004-04-21 devnull 	coord->l = theta*RAD;
 52 28994509 2004-04-21 devnull 	if(theta==90) {
 53 28994509 2004-04-21 devnull 		coord->s = 1;
 54 28994509 2004-04-21 devnull 		coord->c = 0;
 55 28994509 2004-04-21 devnull 	} else if(theta== -90) {
 56 28994509 2004-04-21 devnull 		coord->s = -1;
 57 28994509 2004-04-21 devnull 		coord->c = 0;
 58 28994509 2004-04-21 devnull 	} else
 59 28994509 2004-04-21 devnull 		sincos(coord);
 60 28994509 2004-04-21 devnull }
 61 28994509 2004-04-21 devnull 
 62 28994509 2004-04-21 devnull static double
 63 28994509 2004-04-21 devnull cirmod(double theta)
 64 28994509 2004-04-21 devnull {
 65 28994509 2004-04-21 devnull 	while(theta >= 180.)
 66 28994509 2004-04-21 devnull 		theta -= 360;
 67 28994509 2004-04-21 devnull 	while(theta<-180.)
 68 28994509 2004-04-21 devnull 		theta += 360.;
 69 28994509 2004-04-21 devnull 	return(theta);
 70 28994509 2004-04-21 devnull }
 71 28994509 2004-04-21 devnull 
 72 28994509 2004-04-21 devnull void
 73 28994509 2004-04-21 devnull sincos(struct coord *coord)
 74 28994509 2004-04-21 devnull {
 75 28994509 2004-04-21 devnull 	coord->s = sin(coord->l);
 76 28994509 2004-04-21 devnull 	coord->c = cos(coord->l);
 77 28994509 2004-04-21 devnull }
 78 28994509 2004-04-21 devnull 
 79 28994509 2004-04-21 devnull void
 80 28994509 2004-04-21 devnull normalize(struct place *gg)
 81 28994509 2004-04-21 devnull {
 82 28994509 2004-04-21 devnull 	norm(gg,&pole,&twist);
 83 28994509 2004-04-21 devnull }
 84 28994509 2004-04-21 devnull 
 85 28994509 2004-04-21 devnull void
 86 28994509 2004-04-21 devnull invert(struct place *g)
 87 28994509 2004-04-21 devnull {
 88 28994509 2004-04-21 devnull 	norm(g,&ipole,&itwist);
 89 28994509 2004-04-21 devnull }
 90 28994509 2004-04-21 devnull 
 91 28994509 2004-04-21 devnull void
 92 28994509 2004-04-21 devnull norm(struct place *gg, struct place *pp, struct coord *tw)
 93 28994509 2004-04-21 devnull {
 94 28994509 2004-04-21 devnull 	register struct place *g;	/*geographic coords */
 95 28994509 2004-04-21 devnull 	register struct place *p;	/* new pole in old coords*/
 96 28994509 2004-04-21 devnull 	struct place m;			/* standard map coords*/
 97 28994509 2004-04-21 devnull 	g = gg;
 98 28994509 2004-04-21 devnull 	p = pp;
 99 28994509 2004-04-21 devnull 	if(p->nlat.s == 1.) {
100 28994509 2004-04-21 devnull 		if(p->wlon.l+tw->l == 0.)
101 28994509 2004-04-21 devnull 			return;
102 28994509 2004-04-21 devnull 		g->wlon.l -= p->wlon.l+tw->l;
103 28994509 2004-04-21 devnull 	} else {
104 28994509 2004-04-21 devnull 		if(p->wlon.l != 0) {
105 28994509 2004-04-21 devnull 			g->wlon.l -= p->wlon.l;
106 28994509 2004-04-21 devnull 			sincos(&g->wlon);
107 28994509 2004-04-21 devnull 		}
108 28994509 2004-04-21 devnull 		m.nlat.s = p->nlat.s * g->nlat.s
109 28994509 2004-04-21 devnull 			+ p->nlat.c * g->nlat.c * g->wlon.c;
110 28994509 2004-04-21 devnull 		m.nlat.c = sqrt(1. - m.nlat.s * m.nlat.s);
111 28994509 2004-04-21 devnull 		m.nlat.l = atan2(m.nlat.s, m.nlat.c);
112 28994509 2004-04-21 devnull 		m.wlon.s = g->nlat.c * g->wlon.s;
113 28994509 2004-04-21 devnull 		m.wlon.c = p->nlat.c * g->nlat.s
114 28994509 2004-04-21 devnull 			- p->nlat.s * g->nlat.c * g->wlon.c;
115 28994509 2004-04-21 devnull 		m.wlon.l = atan2(m.wlon.s, - m.wlon.c)
116 28994509 2004-04-21 devnull 			- tw->l;
117 28994509 2004-04-21 devnull 		*g = m;
118 28994509 2004-04-21 devnull 	}
119 28994509 2004-04-21 devnull 	sincos(&g->wlon);
120 28994509 2004-04-21 devnull 	if(g->wlon.l>PI)
121 28994509 2004-04-21 devnull 		g->wlon.l -= 2*PI;
122 28994509 2004-04-21 devnull 	else if(g->wlon.l<-PI)
123 28994509 2004-04-21 devnull 		g->wlon.l += 2*PI;
124 28994509 2004-04-21 devnull }
125 28994509 2004-04-21 devnull 
126 28994509 2004-04-21 devnull void
127 28994509 2004-04-21 devnull printp(struct place *g)
128 28994509 2004-04-21 devnull {
129 28994509 2004-04-21 devnull printf("%.3f %.3f %.3f %.3f %.3f %.3f\n",
130 28994509 2004-04-21 devnull g->nlat.l,g->nlat.s,g->nlat.c,g->wlon.l,g->wlon.s,g->wlon.c);
131 28994509 2004-04-21 devnull }
132 28994509 2004-04-21 devnull 
133 28994509 2004-04-21 devnull void
134 28994509 2004-04-21 devnull copyplace(struct place *g1, struct place *g2)
135 28994509 2004-04-21 devnull {
136 28994509 2004-04-21 devnull 	*g2 = *g1;
137 28994509 2004-04-21 devnull }