src/gen/sun.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 *           SOLAR CALCULATIONS
 *
 *               3/31/87
 *
 */

#include  <math.h>

#define  PI  3.141592654

double  s_latitude = 0.66;      /* site latitude (radians) */
double  s_longitude = 2.13;     /* site longitude (radians) */
double  s_meridian = 2.0944;    /* standard meridian (radians) */


int
jdate(month, day)               /* Julian date (days into year) */
int  month, day;
{
        static short  mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334};
        
        return(mo_da[month-1] + day);
}


double
stadj(jd)               /* solar time adjustment from Julian date */
int  jd;
{
        return( 0.170 * sin( (4*PI/373) * (jd - 80) ) -
                0.129 * sin( (2*PI/355) * (jd - 8) ) +
                12 * (s_meridian - s_longitude) / PI );
}


double
sdec(jd)                /* solar declination angle from Julian date */
int  jd;
{
        return( 0.4093 * sin( (2*PI/368) * (jd - 81) ) );
}


double
salt(sd, st)    /* solar altitude from solar declination and solar time */
double  sd, st;
{
        return( asin( sin(s_latitude) * sin(sd) -
                        cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) );
}


double
sazi(sd, st)    /* solar azimuth from solar declination and solar time */
double  sd, st;
{
        return( -atan2( cos(sd)*sin(st*(PI/12)),
                        -cos(s_latitude)*sin(sd) -
                        sin(s_latitude)*cos(sd)*cos(st*(PI/12)) ) );
}
Revision:	2.3
Committed:	Sat Feb 22 02:07:24 2003 UTC (21 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad3R5
Changes since 2.2:	+1 -4 lines
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
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.3	static const char RCSid[] = "$Id$";
3	greg	1.1	#endif
4	greg	1.2	/*
5	greg	1.1	* SOLAR CALCULATIONS
6			*
7			* 3/31/87
8			*
9			*/
10
11	greg	2.2	#include <math.h>
12
13	greg	1.1	#define PI 3.141592654
14
15			double s_latitude = 0.66; /* site latitude (radians) */
16			double s_longitude = 2.13; /* site longitude (radians) */
17			double s_meridian = 2.0944; /* standard meridian (radians) */
18
19
20			int
21			jdate(month, day) /* Julian date (days into year) */
22			int month, day;
23			{
24			static short mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334};
25
26			return(mo_da[month-1] + day);
27			}
28
29
30			double
31			stadj(jd) /* solar time adjustment from Julian date */
32			int jd;
33			{
34			return( 0.170 * sin( (4PI/373) (jd - 80) ) -
35			0.129 * sin( (2PI/355) (jd - 8) ) +
36			12 * (s_meridian - s_longitude) / PI );
37			}
38
39
40			double
41			sdec(jd) /* solar declination angle from Julian date */
42			int jd;
43			{
44			return( 0.4093 * sin( (2PI/368) (jd - 81) ) );
45			}
46
47
48			double
49			salt(sd, st) /* solar altitude from solar declination and solar time */
50			double sd, st;
51			{
52			return( asin( sin(s_latitude) * sin(sd) -
53			cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) );
54			}
55
56
57			double
58			sazi(sd, st) /* solar azimuth from solar declination and solar time */
59			double sd, st;
60			{
61			return( -atan2( cos(sd)sin(st(PI/12)),
62			-cos(s_latitude)*sin(sd) -
63			sin(s_latitude)cos(sd)cos(st*(PI/12)) ) );
64			}