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root/radiance/ray/src/gen/sun.c
Revision: 2.1
Committed: Tue Nov 12 17:04:42 1991 UTC (32 years, 4 months ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 1.2: +0 -0 lines
Log Message:
updated revision number for release 2.0

File Contents

# Content
1 /* Copyright (c) 1989 Regents of the University of California */
2
3 #ifndef lint
4 static char SCCSid[] = "$SunId$ LBL";
5 #endif
6
7 /*
8 * SOLAR CALCULATIONS
9 *
10 * 3/31/87
11 *
12 */
13
14 #define PI 3.141592654
15
16 double s_latitude = 0.66; /* site latitude (radians) */
17 double s_longitude = 2.13; /* site longitude (radians) */
18 double s_meridian = 2.0944; /* standard meridian (radians) */
19
20
21 int
22 jdate(month, day) /* Julian date (days into year) */
23 int month, day;
24 {
25 static short mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334};
26
27 return(mo_da[month-1] + day);
28 }
29
30
31 double
32 stadj(jd) /* solar time adjustment from Julian date */
33 int jd;
34 {
35 double sin();
36
37 return( 0.170 * sin( (4*PI/373) * (jd - 80) ) -
38 0.129 * sin( (2*PI/355) * (jd - 8) ) +
39 12 * (s_meridian - s_longitude) / PI );
40 }
41
42
43 double
44 sdec(jd) /* solar declination angle from Julian date */
45 int jd;
46 {
47 double sin();
48
49 return( 0.4093 * sin( (2*PI/368) * (jd - 81) ) );
50 }
51
52
53 double
54 salt(sd, st) /* solar altitude from solar declination and solar time */
55 double sd, st;
56 {
57 double sin(), cos(), asin();
58
59 return( asin( sin(s_latitude) * sin(sd) -
60 cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) );
61 }
62
63
64 double
65 sazi(sd, st) /* solar azimuth from solar declination and solar time */
66 double sd, st;
67 {
68 double sin(), cos(), atan2();
69
70 return( -atan2( cos(sd)*sin(st*(PI/12)),
71 -cos(s_latitude)*sin(sd) -
72 sin(s_latitude)*cos(sd)*cos(st*(PI/12)) ) );
73 }