src/gen/sun.c

#ifndef lint
static const char       RCSid[] = "$Id: sun.c,v 2.5 2009/06/06 20:18:32 greg Exp $";
#endif
/*
 *           SOLAR CALCULATIONS
 *
 *               3/31/87
 *
 */

#include  <math.h>
#include  "sun.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:	2.6
Committed:	Fri Aug 9 16:51:15 2013 UTC (10 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad5R2, rad4R2P2, rad5R0, rad5R1, rad4R2, rad4R2P1
Changes since 2.5:	+2 -1 lines
Log Message:	Added header file for solar position calculations
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.6	static const char RCSid[] = "$Id: sun.c,v 2.5 2009/06/06 20:18:32 greg 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	greg	2.6	#include "sun.h"
13	greg	2.2
14	greg	2.5	#ifdef M_PI
15			#define PI M_PI
16			#else
17			#define PI 3.141592653589793
18			#endif
19	greg	1.1
20			double s_latitude = 0.66; /* site latitude (radians) */
21			double s_longitude = 2.13; /* site longitude (radians) */
22			double s_meridian = 2.0944; /* standard meridian (radians) */
23
24
25			int
26	schorsch	2.4	jdate( /* Julian date (days into year) */
27			int month,
28			int day
29			)
30	greg	1.1	{
31			static short mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334};
32
33			return(mo_da[month-1] + day);
34			}
35
36
37			double
38	schorsch	2.4	stadj( /* solar time adjustment from Julian date */
39			int jd
40			)
41	greg	1.1	{
42			return( 0.170 * sin( (4PI/373) (jd - 80) ) -
43			0.129 * sin( (2PI/355) (jd - 8) ) +
44			12 * (s_meridian - s_longitude) / PI );
45			}
46
47
48			double
49	schorsch	2.4	sdec( /* solar declination angle from Julian date */
50			int jd
51			)
52	greg	1.1	{
53			return( 0.4093 * sin( (2PI/368) (jd - 81) ) );
54			}
55
56
57			double
58	schorsch	2.4	salt( /* solar altitude from solar declination and solar time */
59			double sd,
60			double st
61			)
62	greg	1.1	{
63			return( asin( sin(s_latitude) * sin(sd) -
64			cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) );
65			}
66
67
68			double
69	schorsch	2.4	sazi( /* solar azimuth from solar declination and solar time */
70			double sd,
71			double st
72			)
73	greg	1.1	{
74			return( -atan2( cos(sd)sin(st(PI/12)),
75			-cos(s_latitude)*sin(sd) -
76			sin(s_latitude)cos(sd)cos(st*(PI/12)) ) );
77			}