private static double Atan2(double y, double x)
{
double outValue = 0;
if (x < 0)
{
outValue = MathEx.Atan(y / x) + MathEx.PI;
}
if ((x > 0) && (y >= 0))
{
outValue = MathEx.Atan(y / x);
}
if ((x > 0) && (y < 0))
{
outValue = MathEx.Atan(y / x) + 2 * MathEx.PI;
}
if ((x == 0) && (y > 0))
{
outValue = MathEx.PI / 2;
}
if ((x == 0) && (y < 0))
{
outValue = 3 * MathEx.PI / 2;
}
if ((x == 0) && (y == 0))
{
outValue = 0;
}
return(outValue);
}
private int Calculate(Direction direction)
{
// doy (N)
int N = date.DayOfYear;
// appr. time (t)
double lngHour = longitude / 15.0;
double t;
if (direction == Direction.Sunrise)
{
t = N + ((6.0 - lngHour) / 24.0);
}
else
{
t = N + ((18.0 - lngHour) / 24.0);
}
// mean anomaly (M)
double M = (0.9856 * t) - 3.289;
// true longitude (L)
double L = M + (1.916 * MathEx.Sin(Deg2Rad(M))) + (0.020 * MathEx.Sin(Deg2Rad(2 * M))) + 282.634;
L = FixValue(L, 0, 360);
// right asc (RA)
double RA = Rad2Deg(MathEx.Atan(0.91764 * MathEx.Tan(Deg2Rad(L))));
RA = FixValue(RA, 0, 360);
// adjust quadrant of RA
double Lquadrant = (Math.Floor(L / 90.0)) * 90.0;
double RAquadrant = (Math.Floor(RA / 90.0)) * 90.0;
RA = RA + (Lquadrant - RAquadrant);
RA = RA / 15.0;
// sin cos DEC (sinDec / cosDec)
double sinDec = 0.39782 * MathEx.Sin(Deg2Rad(L));
double cosDec = MathEx.Cos(MathEx.Asin(sinDec));
// local hour angle (cosH)
double cosH = (MathEx.Cos(Deg2Rad((double)zenith / 1000.0f)) - (sinDec * MathEx.Sin(Deg2Rad(latitude)))) / (cosDec * MathEx.Cos(Deg2Rad(latitude)));
// local hour (H)
double H;
if (direction == Direction.Sunrise)
{
H = 360.0 - Rad2Deg(MathEx.Acos(cosH));
}
else
{
H = Rad2Deg(MathEx.Acos(cosH));
}
H = H / 15.0;
// time (T)
double T = H + RA - (0.06571 * t) - 6.622;
// universal time (T)
double UT = T - lngHour;
UT += utcOffset; // local UTC offset
if (daylightChanges != null)
{
if ((date > daylightChanges.Start) && (date < daylightChanges.End))
{
UT += (double)daylightChanges.Delta.Ticks / 36000000000;
}
}
UT = FixValue(UT, 0, 24);
return((int)Math.Round(UT * 3600)); // Convert to seconds
}