/// <summary>
/// Returns the sunrise/sunset times at the given location on the specified day
/// </summary>
/// <param name="dt">The requested date/time, utc. Day/night will be computed based on the time</param>
private void ComputeTimesAtLocation(DateTime dt)
{
if (Latitude > 90 || Latitude < -90)
{
throw new MyFlightbookException(Resources.Airports.errInvalidLatitude);
}
if (Longitude > 180 || Longitude < -180)
{
throw new MyFlightbookException(Resources.Airports.errInvalidLongitude);
}
double JD = Solar.calcJD(dt.Year, dt.Month, dt.Day);
DateTime dtUTC = dt.ToUniversalTime();
SolarAngle = Solar.calcSolarAngle(Latitude, Longitude, JD, dtUTC.Hour * 60 + dtUTC.Minute);
IsFAACivilNight = SolarAngle <= -6.0;
Boolean nosunrise = false;
double riseTimeGMT = Solar.calcSunriseUTC(JD, Latitude, -Longitude);
if (double.IsNaN(riseTimeGMT))
{
nosunrise = true;
}
// Calculate sunset for this date
// if no sunset is found, set flag nosunset
Boolean nosunset = false;
double setTimeGMT = Solar.calcSunsetUTC(JD, Latitude, -Longitude);
if (double.IsNaN(setTimeGMT))
{
nosunset = true;
}
// we now know the UTC # of minutes for each. Return the UTC sunrise/sunset times
if (!nosunrise)
{
Sunrise = MinutesToDateTime(dt, riseTimeGMT);
}
if (!nosunset)
{
Sunset = MinutesToDateTime(dt, setTimeGMT);
}
// Update daytime/nighttime
// 3 possible scenarios:
// (a) time is between sunrise/sunset as computed - it's daytime or FAA daytime.
// (b) time is after the sunset - figure out the next sunrise and compare to that
// (c) time is before sunrise - figure out the previous sunset and compare to that
IsNight = IsFAACivilNight;
IsFAANight = false;
IsWithinNightOffset = false;
if (Sunrise.CompareTo(dt) <= 0 && Sunset.CompareTo(dt) >= 0)
{
// between sunrise and sunset - it's daytime no matter how you slice it; use default values (set above)
}
else if (Sunset.CompareTo(dt) < 0)
{
// get the next sunrise. It is night if the time is between sunset and the next sunrise
DateTime dtTomorrow = dt.AddDays(1);
JD = Solar.calcJD(dtTomorrow.Year, dtTomorrow.Month, dtTomorrow.Day);
double nextSunrise = Solar.calcSunriseUTC(JD, Latitude, -Longitude);
if (!double.IsNaN(nextSunrise))
{
DateTime dtNextSunrise = MinutesToDateTime(dtTomorrow, nextSunrise);
IsNight = (dtNextSunrise.CompareTo(dt) > 0); // we've already determined that we're after sunset, we just need to be before sunrise
IsFAANight = (Sunset.AddMinutes(NightLandingOffset).CompareTo(dt) <= 0 && dtNextSunrise.AddMinutes(-NightLandingOffset).CompareTo(dt) >= 0);
IsWithinNightOffset = (Sunset.AddMinutes(NightFlightOffset).CompareTo(dt) <= 0 && dtNextSunrise.AddMinutes(-NightFlightOffset).CompareTo(dt) >= 0);
}
}
else if (Sunrise.CompareTo(dt) > 0)
{
// get the previous sunset. It is night if the time is between that sunset and the sunrise
DateTime dtYesterday = dt.AddDays(-1);
JD = Solar.calcJD(dtYesterday.Year, dtYesterday.Month, dtYesterday.Day);
double prevSunset = Solar.calcSunsetUTC(JD, Latitude, -Longitude);
if (!double.IsNaN(prevSunset))
{
DateTime dtPrevSunset = MinutesToDateTime(dtYesterday, prevSunset);
IsNight = (dtPrevSunset.CompareTo(dt) < 0); // we've already determined that we're before sunrise, we just need to be after sunset.
IsFAANight = (dtPrevSunset.AddMinutes(NightLandingOffset).CompareTo(dt) <= 0 && Sunrise.AddMinutes(-NightLandingOffset).CompareTo(dt) >= 0);
IsWithinNightOffset = (dtPrevSunset.AddMinutes(NightFlightOffset).CompareTo(dt) <= 0 && Sunrise.AddMinutes(-NightFlightOffset).CompareTo(dt) >= 0);
}
}
}
