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{ RCSid $Id: sun.cal,v 1.3 2019/11/07 23:15:06 greg Exp $ } |
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{* |
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* SOLAR CALCULATIONS |
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* |
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* 7/25/84 |
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* 10/10/86 |
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* |
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*} |
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DEG : PI/180; |
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RLAT = 0.66; {* Site latitude (radians) *} |
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RLON = 2.13; {* Site longitude (radians) *} |
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RSM = 120 * DEG; {* Standard meridian (radians) *} |
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stadj(jd) {* solar time adjustment (hours) *} |
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{ jd is days into year } |
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= |
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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*(RSM-RLON)/PI |
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; |
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sdec(jd) {* solar declination angle (radians) *} |
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{ jd is days into year } |
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= |
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0.4093 * sin( 2*PI/365 * (jd - 81) ) |
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; |
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salt(sd, st) {* solar altitude (radians) *} |
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{ sd is solar declination, st is solar time (hours) } |
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= |
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asin( sin(RLAT) * sin(sd) - cos(RLAT) * cos(sd) * |
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cos(PI/12*st) ) |
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; |
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sazi(sd, st) {* the solar azimuth (radians) *} |
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{ sd is solar declination, st is solar time (hours) } |
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= |
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-atan2( cos(sd) * sin(PI/12*st), |
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-cos(RLAT)*sin(sd) - |
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sin(RLAT)*cos(sd)*cos(PI/12*st) ) |
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; |
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SAZI = sazi(SDEC, STIME) / DEG; |
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SALT = salt(SDEC, STIME) / DEG; |
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SDEC = sdec(JDATE); |
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STIME = TIME + stadj(JDATE); |
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HALFDAY = acos(-tan(RLAT)*tan(SDEC)) * (12/PI); |
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JDATE = DAY + select(MONTH,0,31,59,90,120,151,181,212,243,273,304,334); |
