CalendarAstronomer is a class that can perform the calculations to
* determine the positions of the sun and moon, the time of sunrise and
* sunset, and other astronomy-related data. The calculations it performs
* are in some cases quite complicated, and this utility class saves you
* the trouble of worrying about them.
*
* The measurement of time is a very important part of astronomy. Because
* astronomical bodies are constantly in motion, observations are only valid
* at a given moment in time. Accordingly, each CalendarAstronomer
* object has a time property that determines the date
* and time for which its calculations are performed. You can set and
* retrieve this property with {@link #setDate setDate}, {@link #getDate getDate}
* and related methods.
*
* Almost all of the calculations performed by this class, or by any * astronomer, are approximations to various degrees of accuracy. The * calculations in this class are mostly modelled after those described * in the book * * Practical Astronomy With Your Calculator, by Peter J. * Duffett-Smith, Cambridge University Press, 1990. This is an excellent * book, and if you want a greater understanding of how these calculations * are performed it a very good, readable starting point. *
* WARNING: This class is very early in its development, and * it is highly likely that its API will change to some degree in the future. * At the moment, it basically does just enough to support {@link IslamicCalendar} * and {@link ChineseCalendar}. * * @author Laura Werner * @author Alan Liu * @internal */ class U_I18N_API CalendarAstronomer : public UMemory { public: // some classes public: /** * Represents the position of an object in the sky relative to the ecliptic, * the plane of the earth's orbit around the Sun. * This is a spherical coordinate system in which the latitude * specifies the position north or south of the plane of the ecliptic. * The longitude specifies the position along the ecliptic plane * relative to the "First Point of Aries", which is the Sun's position in the sky * at the Vernal Equinox. *
* Note that Ecliptic objects are immutable and cannot be modified * once they are constructed. This allows them to be passed and returned by * value without worrying about whether other code will modify them. * * @see CalendarAstronomer.Equatorial * @see CalendarAstronomer.Horizon * @internal */ class U_I18N_API Ecliptic : public UMemory { public: /** * Constructs an Ecliptic coordinate object. *
* @param lat The ecliptic latitude, measured in radians. * @param lon The ecliptic longitude, measured in radians. * @internal */ Ecliptic(double lat = 0, double lon = 0) { latitude = lat; longitude = lon; } /** * Setter for Ecliptic Coordinate object * @param lat The ecliptic latitude, measured in radians. * @param lon The ecliptic longitude, measured in radians. * @internal */ void set(double lat, double lon) { latitude = lat; longitude = lon; } /** * Return a string representation of this object * @internal */ UnicodeString toString() const; /** * The ecliptic latitude, in radians. This specifies an object's * position north or south of the plane of the ecliptic, * with positive angles representing north. * @internal */ double latitude; /** * The ecliptic longitude, in radians. * This specifies an object's position along the ecliptic plane * relative to the "First Point of Aries", which is the Sun's position * in the sky at the Vernal Equinox, * with positive angles representing east. *
* A bit of trivia: the first point of Aries is currently in the * constellation Pisces, due to the precession of the earth's axis. * @internal */ double longitude; }; /** * Represents the position of an * object in the sky relative to the plane of the earth's equator. * The Right Ascension specifies the position east or west * along the equator, relative to the sun's position at the vernal * equinox. The Declination is the position north or south * of the equatorial plane. *
* Note that Equatorial objects are immutable and cannot be modified * once they are constructed. This allows them to be passed and returned by * value without worrying about whether other code will modify them. * * @see CalendarAstronomer.Ecliptic * @see CalendarAstronomer.Horizon * @internal */ class U_I18N_API Equatorial : public UMemory { public: /** * Constructs an Equatorial coordinate object. *
* @param asc The right ascension, measured in radians. * @param dec The declination, measured in radians. * @internal */ Equatorial(double asc = 0, double dec = 0) : ascension(asc), declination(dec) { } /** * Setter * @param asc The right ascension, measured in radians. * @param dec The declination, measured in radians. * @internal */ void set(double asc, double dec) { ascension = asc; declination = dec; } /** * Return a string representation of this object, with the * angles measured in degrees. * @internal */ UnicodeString toString() const; /** * Return a string representation of this object with the right ascension * measured in hours, minutes, and seconds. * @internal */ //String toHmsString() { //return radToHms(ascension) + "," + radToDms(declination); //} /** * The right ascension, in radians. * This is the position east or west along the equator * relative to the sun's position at the vernal equinox, * with positive angles representing East. * @internal */ double ascension; /** * The declination, in radians. * This is the position north or south of the equatorial plane, * with positive angles representing north. * @internal */ double declination; }; /** * Represents the position of an object in the sky relative to * the local horizon. * The Altitude represents the object's elevation above the horizon, * with objects below the horizon having a negative altitude. * The Azimuth is the geographic direction of the object from the * observer's position, with 0 representing north. The azimuth increases * clockwise from north. *
* Note that Horizon objects are immutable and cannot be modified * once they are constructed. This allows them to be passed and returned by * value without worrying about whether other code will modify them. * * @see CalendarAstronomer.Ecliptic * @see CalendarAstronomer.Equatorial * @internal */ class U_I18N_API Horizon : public UMemory { public: /** * Constructs a Horizon coordinate object. *
* @param alt The altitude, measured in radians above the horizon.
* @param azim The azimuth, measured in radians clockwise from north.
* @internal
*/
Horizon(double alt=0, double azim=0)
: altitude(alt), azimuth(azim) { }
/**
* Setter for Ecliptic Coordinate object
* @param alt The altitude, measured in radians above the horizon.
* @param azim The azimuth, measured in radians clockwise from north.
* @internal
*/
void set(double alt, double azim) {
altitude = alt;
azimuth = azim;
}
/**
* Return a string representation of this object, with the
* angles measured in degrees.
* @internal
*/
UnicodeString toString() const;
/**
* The object's altitude above the horizon, in radians.
* @internal
*/
double altitude;
/**
* The object's direction, in radians clockwise from north.
* @internal
*/
double azimuth;
};
public:
//-------------------------------------------------------------------------
// Assorted private data used for conversions
//-------------------------------------------------------------------------
// My own copies of these so compilers are more likely to optimize them away
static const double PI;
/**
* The average number of solar days from one new moon to the next. This is the time
* it takes for the moon to return the same ecliptic longitude as the sun.
* It is longer than the sidereal month because the sun's longitude increases
* during the year due to the revolution of the earth around the sun.
* Approximately 29.53.
*
* @see #SIDEREAL_MONTH
* @internal
* @deprecated ICU 2.4. This class may be removed or modified.
*/
static const double SYNODIC_MONTH;
//-------------------------------------------------------------------------
// Constructors
//-------------------------------------------------------------------------
/**
* Construct a new CalendarAstronomer object that is initialized to
* the current date and time.
* @internal
*/
CalendarAstronomer();
/**
* Construct a new CalendarAstronomer object that is initialized to
* the specified date and time.
* @internal
*/
CalendarAstronomer(UDate d);
/**
* Construct a new CalendarAstronomer object with the given
* latitude and longitude. The object's time is set to the current
* date and time.
*
* @param longitude The desired longitude, in degrees east of
* the Greenwich meridian.
*
* @param latitude The desired latitude, in degrees. Positive
* values signify North, negative South.
*
* @see java.util.Date#getTime()
* @internal
*/
CalendarAstronomer(double longitude, double latitude);
/**
* Destructor
* @internal
*/
~CalendarAstronomer();
//-------------------------------------------------------------------------
// Time and date getters and setters
//-------------------------------------------------------------------------
/**
* Set the current date and time of this CalendarAstronomer object. All
* astronomical calculations are performed based on this time setting.
*
* @param aTime the date and time, expressed as the number of milliseconds since
* 1/1/1970 0:00 GMT (Gregorian).
*
* @see #setDate
* @see #getTime
* @internal
*/
void setTime(UDate aTime);
/**
* Set the current date and time of this CalendarAstronomer object. All
* astronomical calculations are performed based on this time setting.
*
* @param aTime the date and time, expressed as the number of milliseconds since
* 1/1/1970 0:00 GMT (Gregorian).
*
* @see #getTime
* @internal
*/
void setDate(UDate aDate) { setTime(aDate); }
/**
* Set the current date and time of this CalendarAstronomer object. All
* astronomical calculations are performed based on this time setting.
*
* @param jdn the desired time, expressed as a "julian day number",
* which is the number of elapsed days since
* 1/1/4713 BC (Julian), 12:00 GMT. Note that julian day
* numbers start at noon. To get the jdn for
* the corresponding midnight, subtract 0.5.
*
* @see #getJulianDay
* @see #JULIAN_EPOCH_MS
* @internal
*/
void setJulianDay(double jdn);
/**
* Get the current time of this CalendarAstronomer object,
* represented as the number of milliseconds since
* 1/1/1970 AD 0:00 GMT (Gregorian).
*
* @see #setTime
* @see #getDate
* @internal
*/
UDate getTime();
/**
* Get the current time of this CalendarAstronomer object,
* expressed as a "julian day number", which is the number of elapsed
* days since 1/1/4713 BC (Julian), 12:00 GMT.
*
* @see #setJulianDay
* @see #JULIAN_EPOCH_MS
* @internal
*/
double getJulianDay();
/**
* Return this object's time expressed in julian centuries:
* the number of centuries after 1/1/1900 AD, 12:00 GMT
*
* @see #getJulianDay
* @internal
*/
double getJulianCentury();
/**
* Returns the current Greenwich sidereal time, measured in hours
* @internal
*/
double getGreenwichSidereal();
private:
double getSiderealOffset();
public:
/**
* Returns the current local sidereal time, measured in hours
* @internal
*/
double getLocalSidereal();
/**
* Converts local sidereal time to Universal Time.
*
* @param lst The Local Sidereal Time, in hours since sidereal midnight
* on this object's current date.
*
* @return The corresponding Universal Time, in milliseconds since
* 1 Jan 1970, GMT.
*/
//private:
double lstToUT(double lst);
/**
*
* Convert from ecliptic to equatorial coordinates.
*
* @param ecliptic The ecliptic
* @param result Fillin result
* @return reference to result
*/
Equatorial& eclipticToEquatorial(Equatorial& result, const Ecliptic& ecliptic);
/**
* Convert from ecliptic to equatorial coordinates.
*
* @param eclipLong The ecliptic longitude
* @param eclipLat The ecliptic latitude
*
* @return The corresponding point in equatorial coordinates.
* @internal
*/
Equatorial& eclipticToEquatorial(Equatorial& result, double eclipLong, double eclipLat);
/**
* Convert from ecliptic longitude to equatorial coordinates.
*
* @param eclipLong The ecliptic longitude
*
* @return The corresponding point in equatorial coordinates.
* @internal
*/
Equatorial& eclipticToEquatorial(Equatorial& result, double eclipLong) ;
/**
* @internal
*/
Horizon& eclipticToHorizon(Horizon& result, double eclipLong) ;
//-------------------------------------------------------------------------
// The Sun
//-------------------------------------------------------------------------
/**
* The longitude of the sun at the time specified by this object.
* The longitude is measured in radians along the ecliptic
* from the "first point of Aries," the point at which the ecliptic
* crosses the earth's equatorial plane at the vernal equinox.
*
* Currently, this method uses an approximation of the two-body Kepler's
* equation for the earth and the sun. It does not take into account the
* perturbations caused by the other planets, the moon, etc.
* @internal
*/
double getSunLongitude();
/**
* TODO Make this public when the entire class is package-private.
*/
/*public*/ void getSunLongitude(double julianDay, double &longitude, double &meanAnomaly);
/**
* The position of the sun at this object's current date and time,
* in equatorial coordinates.
* @param result fillin for the result
* @internal
*/
Equatorial& getSunPosition(Equatorial& result);
public:
/**
* Constant representing the vernal equinox.
* For use with {@link #getSunTime getSunTime}.
* Note: In this case, "vernal" refers to the northern hemisphere's seasons.
* @internal
*/
// static double VERNAL_EQUINOX();
/**
* Constant representing the summer solstice.
* For use with {@link #getSunTime getSunTime}.
* Note: In this case, "summer" refers to the northern hemisphere's seasons.
* @internal
*/
static double SUMMER_SOLSTICE();
/**
* Constant representing the autumnal equinox.
* For use with {@link #getSunTime getSunTime}.
* Note: In this case, "autumn" refers to the northern hemisphere's seasons.
* @internal
*/
// static double AUTUMN_EQUINOX();
/**
* Constant representing the winter solstice.
* For use with {@link #getSunTime getSunTime}.
* Note: In this case, "winter" refers to the northern hemisphere's seasons.
* @internal
*/
static double WINTER_SOLSTICE();
/**
* Find the next time at which the sun's ecliptic longitude will have
* the desired value.
* @internal
*/
UDate getSunTime(double desired, UBool next);
/**
* Returns the time (GMT) of sunrise or sunset on the local date to which
* this calendar is currently set.
*
* NOTE: This method only works well if this object is set to a
* time near local noon. Because of variations between the local
* official time zone and the geographic longitude, the
* computation can flop over into an adjacent day if this object
* is set to a time near local midnight.
*
* @internal
*/
UDate getSunRiseSet(UBool rise);
//-------------------------------------------------------------------------
// The Moon
//-------------------------------------------------------------------------
/**
* The position of the moon at the time set on this
* object, in equatorial coordinates.
* @internal
* @return const reference to internal field of calendar astronomer. Do not use outside of the lifetime of this astronomer.
*/
const Equatorial& getMoonPosition();
/**
* The "age" of the moon at the time specified in this object.
* This is really the angle between the
* current ecliptic longitudes of the sun and the moon,
* measured in radians.
*
* @see #getMoonPhase
* @internal
*/
double getMoonAge();
/**
* Calculate the phase of the moon at the time set in this object.
* The returned phase is a double in the range
* 0 <= phase < 1, interpreted as follows:
*
* @param desired The desired longitude. * @param next true if the next occurrence of the phase * is desired, false for the previous occurrence. * @internal */ UDate getMoonTime(double desired, UBool next); UDate getMoonTime(const MoonAge& desired, UBool next); /** * Returns the time (GMT) of sunrise or sunset on the local date to which * this calendar is currently set. * @internal */ UDate getMoonRiseSet(UBool rise); //------------------------------------------------------------------------- // Interpolation methods for finding the time at which a given event occurs //------------------------------------------------------------------------- // private class AngleFunc : public UMemory { public: virtual double eval(CalendarAstronomer&) = 0; virtual ~AngleFunc(); }; friend class AngleFunc; UDate timeOfAngle(AngleFunc& func, double desired, double periodDays, double epsilon, UBool next); class CoordFunc : public UMemory { public: virtual void eval(Equatorial& result, CalendarAstronomer&) = 0; virtual ~CoordFunc(); }; friend class CoordFunc; double riseOrSet(CoordFunc& func, UBool rise, double diameter, double refraction, double epsilon); //------------------------------------------------------------------------- // Other utility methods //------------------------------------------------------------------------- private: /** * Return the obliquity of the ecliptic (the angle between the ecliptic * and the earth's equator) at the current time. This varies due to * the precession of the earth's axis. * * @return the obliquity of the ecliptic relative to the equator, * measured in radians. */ double eclipticObliquity(); //------------------------------------------------------------------------- // Private data //------------------------------------------------------------------------- private: /** * Current time in milliseconds since 1/1/1970 AD * @see java.util.Date#getTime */ UDate fTime; /* These aren't used yet, but they'll be needed for sunset calculations * and equatorial to horizon coordinate conversions */ double fLongitude; double fLatitude; double fGmtOffset; // // The following fields are used to cache calculated results for improved // performance. These values all depend on the current time setting // of this object, so the clearCache method is provided. // double julianDay; double julianCentury; double sunLongitude; double meanAnomalySun; double moonLongitude; double moonEclipLong; double meanAnomalyMoon; double eclipObliquity; double siderealT0; double siderealTime; void clearCache(); Equatorial moonPosition; UBool moonPositionSet; /** * @internal */ // UDate local(UDate localMillis); }; U_NAMESPACE_END struct UHashtable; U_NAMESPACE_BEGIN /** * Cache of month -> julian day * @internal */ class CalendarCache : public UMemory { public: static int32_t get(CalendarCache** cache, int32_t key, UErrorCode &status); static void put(CalendarCache** cache, int32_t key, int32_t value, UErrorCode &status); virtual ~CalendarCache(); private: CalendarCache(int32_t size, UErrorCode& status); static void createCache(CalendarCache** cache, UErrorCode& status); /** * not implemented */ CalendarCache(); UHashtable *fTable; }; U_NAMESPACE_END #endif #endif