src/gen/sun.c

#ifndef lint
static const char       RCSid[] = "$Id: sun.c,v 2.4 2003/11/16 10:29:38 schorsch Exp $";
#endif
/*
 *           SOLAR CALCULATIONS
 *
 *               3/31/87
 *
 */

#include  <math.h>

#ifdef M_PI
#define  PI     M_PI
#else
#define  PI     3.141592653589793
#endif

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(          /* Julian date (days into year) */
        int month,
        int 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(          /* 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(           /* solar declination angle from Julian date */
        int  jd
)
{
        return( 0.4093 * sin( (2*PI/368) * (jd - 81) ) );
}


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


double
sazi(   /* solar azimuth from solar declination and solar time */
        double sd,
        double st
)
{
        return( -atan2( cos(sd)*sin(st*(PI/12)),
                        -cos(s_latitude)*sin(sd) -
                        sin(s_latitude)*cos(sd)*cos(st*(PI/12)) ) );
}
Revision:	2.5
Committed:	Sat Jun 6 20:18:32 2009 UTC (16 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad4R1, rad4R0
Changes since 2.4:	+6 -2 lines
Log Message:	Added Jean-Jacques Delaunay's gendaylit program to distribution
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.5	static const char RCSid[] = "$Id: sun.c,v 2.4 2003/11/16 10:29:38 schorsch Exp $";
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	2.5	#ifdef M_PI
14			#define PI M_PI
15			#else
16			#define PI 3.141592653589793
17			#endif
18	greg	1.1
19			double s_latitude = 0.66; /* site latitude (radians) */
20			double s_longitude = 2.13; /* site longitude (radians) */
21			double s_meridian = 2.0944; /* standard meridian (radians) */
22
23
24			int
25	schorsch	2.4	jdate( /* Julian date (days into year) */
26			int month,
27			int day
28			)
29	greg	1.1	{
30			static short mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334};
31
32			return(mo_da[month-1] + day);
33			}
34
35
36			double
37	schorsch	2.4	stadj( /* solar time adjustment from Julian date */
38			int jd
39			)
40	greg	1.1	{
41			return( 0.170 * sin( (4PI/373) (jd - 80) ) -
42			0.129 * sin( (2PI/355) (jd - 8) ) +
43			12 * (s_meridian - s_longitude) / PI );
44			}
45
46
47			double
48	schorsch	2.4	sdec( /* solar declination angle from Julian date */
49			int jd
50			)
51	greg	1.1	{
52			return( 0.4093 * sin( (2PI/368) (jd - 81) ) );
53			}
54
55
56			double
57	schorsch	2.4	salt( /* solar altitude from solar declination and solar time */
58			double sd,
59			double st
60			)
61	greg	1.1	{
62			return( asin( sin(s_latitude) * sin(sd) -
63			cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) );
64			}
65
66
67			double
68	schorsch	2.4	sazi( /* solar azimuth from solar declination and solar time */
69			double sd,
70			double st
71			)
72	greg	1.1	{
73			return( -atan2( cos(sd)sin(st(PI/12)),
74			-cos(s_latitude)*sin(sd) -
75			sin(s_latitude)cos(sd)cos(st*(PI/12)) ) );
76			}