// this is not used effectovely
// it is just try to have some alternative function for calculation sun position
// but it needs to be fixed, because
// it calculates correct ecliptical coordinates, but when transforming
// into horizontal coordinates (azimut, elevation) it will do something wrong
public static GCHorizontalCoords sunPosition(int year, int month, int day, int hour, int min, int sec,
double lat, double longi)
{
double twopi = GCMath.PI2;
double deg2rad = GCMath.PI2 / 180;
int[] month_days = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30 };
for (int y2 = 0; y2 < month; y2++)
{
day += month_days[y2];
}
if ((year % 4 == 0) && ((year % 400 == 0) || (year % 100 != 0)) && (day >= 60) && !(month == 2 & day == 60))
{
day++;
}
//# Get Julian date - 2400000
double hourd = hour + min / 60.0 + sec / 3600.0; // hour plus fraction
double delta = year - 1949;
double leap = Math.Floor(delta / 4); // former leapyears
double jd = 32916.5 + delta * 365 + leap + day + hourd / 24.0;
// The input to the Atronomer's almanach is the difference between
// the Julian date and JD 2451545.0 (noon, 1 January 2000)
double time = jd - 51545.0;
// Ecliptic coordinates
// Mean longitude
double mnlong = GCMath.putIn360(280.460 + .9856474 * time);
// Mean anomaly
double mnanom = GCMath.putIn360(357.528 + .9856003 * time);
//mnanom <- mnanom * deg2rad
// Ecliptic longitude and obliquity of ecliptic
double eclong = mnlong + 1.915 * GCMath.sinDeg(mnanom) + 0.020 * GCMath.sinDeg(2 * mnanom);
eclong = GCMath.putIn360(eclong);
double oblqec = 23.439 - 0.0000004 * time;
//-- eclong <- eclong * deg2rad
//-- oblqec <- oblqec * deg2rad
// Celestial coordinates
// Right ascension and declination
double num = GCMath.cosDeg(oblqec) * GCMath.sinDeg(eclong);
double den = GCMath.cosDeg(eclong);
double ra = GCMath.arcTan2Deg(num, den);
while (ra < 0)
{
ra += 180;
}
//-- ra[den < 0] <- ra[den < 0] + pi
if (den >= 0 && num < 0)
{
ra += 360;
}
double dec = GCMath.arcSinDeg(GCMath.sinDeg(oblqec) * GCMath.sinDeg(eclong));
// Local coordinates
// Greenwich mean sidereal time
double gmst = 6.697375 + .0657098242 * time + hourd;
gmst = GCMath.putIn24(gmst);
// Local mean sidereal time
double lmst = gmst + longi / 15.0;
lmst = GCMath.putIn24(lmst);
lmst = lmst * 15.0;
// Hour angle
double ha = lmst - ra;
ha = GCMath.putIn180(ha);
// Azimuth and elevation
double el = GCMath.arcSinDeg(GCMath.sinDeg(dec) * GCMath.sinDeg(lat) + GCMath.cosDeg(dec) * GCMath.cosDeg(lat) * GCMath.cosDeg(ha));
double az = GCMath.arcSinDeg(-GCMath.cosDeg(dec) * GCMath.sinDeg(ha) / GCMath.cosDeg(el));
//# -----------------------------------------------
//# New code
//# Solar zenith angle
double zenithAngle = GCMath.arccosDeg(GCMath.sinDeg(lat) * GCMath.sinDeg(dec) + GCMath.cosDeg(lat) * GCMath.cosDeg(dec) * GCMath.cosDeg(ha));
//# Solar azimuth
az = GCMath.arccosDeg(((GCMath.sinDeg(lat) * GCMath.cosDeg(zenithAngle)) - GCMath.sinDeg(dec)) / (GCMath.cosDeg(lat) * GCMath.sinDeg(zenithAngle)));
//# -----------------------------------------------
//# Azimuth and elevation
el = GCMath.arcSinDeg(GCMath.sinDeg(dec) * GCMath.sinDeg(lat) + GCMath.cosDeg(dec) * GCMath.cosDeg(lat) * GCMath.cosDeg(ha));
//# -----------------------------------------------
//# New code
if (ha > 0)
{
az += 180;
}
else
{
az = 540 - az;
}
az = GCMath.putIn360(az);
// For logic and names, see Spencer, J.W. 1989. Solar Energy. 42(4):353
//cosAzPos <- (0 <= sin(dec) - sin(el) * sin(lat))
//sinAzNeg <- (sin(az) < 0)
//az[cosAzPos & sinAzNeg] <- az[cosAzPos & sinAzNeg] + twopi
//az[!cosAzPos] <- pi - az[!cosAzPos]
/*
* if (0 < GCMath.sinDeg(dec) - GCMath.sinDeg(el) * GCMath.sinDeg(lat))
* {
* if(GCMath.sinDeg(az) < 0)
* {
* az = az + 360;
* }
* }
* else
* {
* az = 180 - az;
* }
*/
//el <- el / deg2rad
//az <- az / deg2rad
//lat <- lat / deg2rad
GCHorizontalCoords coords;
coords.azimut = az;
coords.elevation = el;
return(coords);
}
