void DashboardInstrument_Sun::calculateSun(double latit, double longit, wxDateTime &sunrise, wxDateTime &sunset){
/*
Source:
Almanac for Computers, 1990
published by Nautical Almanac Office
United States Naval Observatory
Washington, DC 20392
Inputs:
day, month, year: date of sunrise/sunset
latitude, longitude: location for sunrise/sunset
zenith: Sun's zenith for sunrise/sunset
offical = 90 degrees 50'
civil = 96 degrees
nautical = 102 degrees
astronomical = 108 degrees
NOTE: longitude is positive for East and negative for West
NOTE: the algorithm assumes the use of a calculator with the
trig functions in "degree" (rather than "radian") mode. Most
programming languages assume radian arguments, requiring back
and forth convertions. The factor is 180/pi. So, for instance,
the equation RA = atan(0.91764 * tan(L)) would be coded as RA
= (180/pi)*atan(0.91764 * tan((pi/180)*L)) to give a degree
answer with a degree input for L.
1. first calculate the day of the year
N1 = floor(275 * month / 9)
N2 = floor((month + 9) / 12)
N3 = (1 + floor((year - 4 * floor(year / 4) + 2) / 3))
N = N1 - (N2 * N3) + day - 30
*/
int n = m_dt.GetDayOfYear();
/*
2. convert the longitude to hour value and calculate an approximate time
lngHour = longitude / 15
if rising time is desired:
t = N + ((6 - lngHour) / 24)
if setting time is desired:
t = N + ((18 - lngHour) / 24)
*/
double lngHour = longit / 15;
double tris = n + ((6 - lngHour) / 24);
double tset = n + ((18 - lngHour) / 24);
/*
3. calculate the Sun's mean anomaly
M = (0.9856 * t) - 3.289
*/
double mris = (0.9856 * tris) - 3.289;
double mset = (0.9856 * tset) - 3.289;
/*
4. calculate the Sun's true longitude
L = M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634
NOTE: L potentially needs to be adjusted into the range [0,360) by adding/subtracting 360
*/
double lris = mris + (1.916 * sin(DEGREE * mris)) + (0.020 * sin(2 * DEGREE * mris)) + 282.634;
if (lris > 360) lris -= 360;
if (lris < 0) lris += 360;
double lset = mset + (1.916 * sin(DEGREE * mset)) + (0.020 * sin(2 * DEGREE * mset)) + 282.634;
if (lset > 360) lset -= 360;
if (lset < 0) lset += 360;
/*
5a. calculate the Sun's right ascension
RA = atan(0.91764 * tan(L))
NOTE: RA potentially needs to be adjusted into the range [0,360) by adding/subtracting 360
*/
double raris = RADIAN * atan(0.91764 * tan(DEGREE * lris));
if (raris > 360) raris -= 360;
if (raris < 0) raris += 360;
double raset = RADIAN * atan(0.91764 * tan(DEGREE * lset));
if (raset > 360) raset -= 360;
if (raset < 0) raset += 360;
/*
5b. right ascension value needs to be in the same quadrant as L
Lquadrant = (floor( L/90)) * 90
RAquadrant = (floor(RA/90)) * 90
RA = RA + (Lquadrant - RAquadrant)
*/
double lqris = (floor( lris/90)) * 90;
double raqris = (floor(raris/90)) * 90;
raris = raris + (lqris - raqris);
double lqset = (floor( lset/90)) * 90;
double raqset = (floor(raset/90)) * 90;
raset = raset + (lqset - raqset);
/*
5c. right ascension value needs to be converted into hours
RA = RA / 15
*/
raris = raris/15;
raset = raset/15;
/*
6. calculate the Sun's declination
sinDec = 0.39782 * sin(L)
cosDec = cos(asin(sinDec))
*/
double sinDecris = 0.39782 * sin(DEGREE * lris);
double cosDecris = cos(asin(sinDecris));
double sinDecset = 0.39782 * sin(DEGREE * lset);
double cosDecset = cos(asin(sinDecset));
/*
7a. calculate the Sun's local hour angle
cosH = (cos(zenith) - (sinDec * sin(latitude))) / (cosDec * cos(latitude))
if (cosH > 1)
the sun never rises on this location (on the specified date)
if (cosH < -1)
the sun never sets on this location (on the specified date)
*/
double cosZenith = cos(DEGREE * ZENITH_OFFICIAL);
double coshris = (cosZenith - (sinDecris * sin(DEGREE * latit))) / (cosDecris * cos(DEGREE * latit));
double coshset = (cosZenith - (sinDecset * sin(DEGREE * latit))) / (cosDecset * cos(DEGREE * latit));
bool neverrises = false;
if (coshris > 1) neverrises = true;
if (coshris < -1) neverrises = true; //nohal - it's cosine - even value lower than -1 is ilegal... correct me if i'm wrong
bool neversets = false;
if (coshset < -1) neversets = true;
if (coshset > 1) neversets = true; //nohal - it's cosine - even value greater than 1 is ilegal... correct me if i'm wrong
/*
7b. finish calculating H and convert into hours
if if rising time is desired:
H = 360 - acos(cosH)
if setting time is desired:
H = acos(cosH)
H = H / 15
*/
double hris = 360 - RADIAN * acos(coshris);
hris = hris/15;
double hset = RADIAN * acos(coshset);
hset = hset/15;
/*
8. calculate local mean time of rising/setting
T = H + RA - (0.06571 * t) - 6.622
*/
tris = hris + raris - (0.06571 * tris) - 6.622;
tset = hset + raset - (0.06571 * tset) - 6.622;
/*
9. adjust back to UTC
UT = T - lngHour
NOTE: UT potentially needs to be adjusted into the range [0,24) by adding/subtracting 24
*/
double utris = tris - lngHour;
if (utris > 24) utris -= 24;
if (utris <0) utris += 24;
double utset = tset - lngHour;
if (utset > 24) utset -= 24;
if (utset <0) utset += 24;
sunrise = convHrmn(utris);
if (neverrises) sunrise.SetYear(999);
sunset = convHrmn(utset);
if (neversets) sunset.SetYear(999);
/*
Optional:
10. convert UT value to local time zone of latitude/longitude
localT = UT + localOffset
*/
}
