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root/radiance/ray/src/cal/cal/sun.cal
Revision: 1.1
Committed: Sat Feb 22 02:07:21 2003 UTC (21 years, 1 month ago) by greg
Branch: MAIN
CVS Tags: rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R5, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1
Log Message: 
Changes and check-in for 3.5 release
Includes new source files and modifications not recorded for many years
See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release

File Contents

# Content
1 {*
2 * SOLAR CALCULATIONS
3 *
4 * 7/25/84
5 * 10/10/86
6 *
7 *}
8
9 RLAT = 0.66; {* Site latitude (radians) *}
10
11 RLON = 2.13; {* Site longitude (radians) *}
12
13 RSM = 120 * PI/180; {* Standard meridian (radians) *}
14
15
16 stadj(jd) {* solar time adjustment (hours) *}
17 { jd is days into year }
18 =
19 0.170 * sin( 4*PI/373 * (jd - 80) ) -
20 0.129 * sin( 2*PI/355 * (jd - 8 ) ) +
21 12*(RSM-RLON)/PI
22 ;
23
24
25 sdec(jd) {* solar declination angle (radians) *}
26 { jd is days into year }
27 =
28 0.4093 * sin( 2*PI/368 * (jd - 81) )
29 ;
30
31
32 salt(sd, st) {* solar altitude (radians) *}
33 { sd is solar declination, st is solar time (hours) }
34 =
35 asin( sin(RLAT) * sin(sd) - cos(RLAT) * cos(sd) *
36 cos(st*PI/12) )
37 ;
38
39
40 sazi(sd, st) {* the solar azimuth (radians) *}
41 { sd is solar declination, st is solar time (hours) }
42 =
43 -atan2( cos(sd) * sin(st*PI/12),
44 -cos(RLAT)*sin(sd) -
45 sin(RLAT)*cos(sd)*cos(st*PI/12) )
46 ;
47
48
49 SAZI = sazi(SDEC, STIME) * 180/PI;
50
51 SALT = salt(SDEC, STIME) * 180/PI;
52
53 SDEC = sdec(JDATE);
54
55 STIME = TIME + stadj(JDATE);
56
57 JDATE = DAY + select(MONTH,0,31,59,90,120,151,181,212,243,273,304,334);