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#ifndef lint |
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static const char RCSid[] = "$Id: sun.c,v 2.3 2003/02/22 02:07:24 greg Exp $"; |
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#endif |
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/* |
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* SOLAR CALCULATIONS |
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* |
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* 3/31/87 |
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* |
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*/ |
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|
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#include <math.h> |
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|
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#define PI 3.141592654 |
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|
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double s_latitude = 0.66; /* site latitude (radians) */ |
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double s_longitude = 2.13; /* site longitude (radians) */ |
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double s_meridian = 2.0944; /* standard meridian (radians) */ |
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|
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|
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int |
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jdate( /* Julian date (days into year) */ |
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int month, |
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int day |
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) |
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{ |
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static short mo_da[12] = {0,31,59,90,120,151,181,212,243,273,304,334}; |
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|
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return(mo_da[month-1] + day); |
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} |
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|
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|
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double |
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stadj( /* solar time adjustment from Julian date */ |
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int jd |
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) |
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{ |
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return( 0.170 * sin( (4*PI/373) * (jd - 80) ) - |
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0.129 * sin( (2*PI/355) * (jd - 8) ) + |
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12 * (s_meridian - s_longitude) / PI ); |
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} |
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|
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|
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double |
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sdec( /* solar declination angle from Julian date */ |
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int jd |
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) |
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{ |
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return( 0.4093 * sin( (2*PI/368) * (jd - 81) ) ); |
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} |
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|
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|
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double |
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salt( /* solar altitude from solar declination and solar time */ |
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double sd, |
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double st |
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) |
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{ |
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return( asin( sin(s_latitude) * sin(sd) - |
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cos(s_latitude) * cos(sd) * cos(st*(PI/12)) ) ); |
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} |
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|
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|
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double |
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sazi( /* solar azimuth from solar declination and solar time */ |
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double sd, |
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double st |
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) |
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{ |
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return( -atan2( cos(sd)*sin(st*(PI/12)), |
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-cos(s_latitude)*sin(sd) - |
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sin(s_latitude)*cos(sd)*cos(st*(PI/12)) ) ); |
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} |
