Class NOAACalculator

java.lang.Object

com.kosherjava.zmanim.util.AstronomicalCalculator

com.kosherjava.zmanim.util.NOAACalculator

All Implemented Interfaces:

Cloneable

public class NOAACalculator
extends AstronomicalCalculator

Implementation of sunrise and sunset methods to calculate astronomical times based on the NOAA algorithm. This calculator uses the Java algorithm based on the implementation by NOAA - National Oceanic and Atmospheric Administration's Surface Radiation Research Branch. NOAA's implementation is based on equations from Astronomical Algorithms by Jean Meeus. Added to the algorithm is an adjustment of the zenith to account for elevation. The algorithm can be found in the Wikipedia Sunrise Equation article.

Author:

© Eliyahu Hershfeld 2011 - 2025

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static enum	NOAACalculator.SolarEvent	An enum to indicate what type of solar event (SUNRISE, SUNSET, NOON or MIDNIGHT) is being calculated. .

Field Summary

Fields

Modifier and Type	Field	Description
private static final double	JULIAN_DAY_JAN_1_2000	The Julian day of January 1, 2000, known as J2000.0.
private static final double	JULIAN_DAYS_PER_CENTURY	Julian days per century.

Constructor Summary

Constructors

Constructor	Description
NOAACalculator()	Default constructor of the NOAACalculator.

Method Summary

Modifier and Type	Method	Description
private int	adjustHourForTimeZone(Calendar calendar)	Returns the hour of day adjusted for the timezone and DST.
String	getCalculatorName()	Returns the name of the algorithm.
private static double	getEarthOrbitEccentricity(double julianCenturies)	Return the unitless eccentricity of earth's orbit.
private static double	getEquationOfTime(double julianCenturies)	Return the Equation of Time - the difference between true solar time and mean solar time
private static double	getJulianCenturiesFromJulianDay(double julianDay)	Convert Julian day to centuries since J2000.0.
private static double	getJulianDay(Calendar calendar)	Return the Julian day from a Java Calendar.
private static double	getMeanObliquityOfEcliptic(double julianCenturies)	Returns the mean obliquity of the ecliptic (Axial tilt).
private static double	getObliquityCorrection(double julianCenturies)	Returns the corrected obliquity of the ecliptic (Axial tilt).
double	getSolarAzimuth(Calendar calendar, GeoLocation geoLocation)	Return the Solar Azimuth for the horizontal coordinate system at the given location at the given time.
double	getSolarElevation(Calendar calendar, GeoLocation geoLocation)	Return the Solar Elevation for the horizontal coordinate system at the given location at the given time.
private double	getSolarElevationAzimuth(Calendar calendar, GeoLocation geoLocation, boolean isAzimuth)	Return the Solar Elevation or Solar Azimuth at the given location and time.
private static double	getSolarNoonMidnightUTC(double julianDay, double longitude, NOAACalculator.SolarEvent solarEvent)	Return the Universal Coordinated Time (UTC) of the current day solar noon or the the upcoming midnight (about 12 hours after solar noon) of the given day at the given location on earth.
private static double	getSunApparentLongitude(double julianCenturies)	Return the apparent longitude of the sun.
private static double	getSunDeclination(double julianCenturies)	Return the declination of the sun.
private static double	getSunEquationOfCenter(double julianCenturies)	Returns the equation of center for the sun in degrees.
private static double	getSunGeometricMeanAnomaly(double julianCenturies)	Returns the Geometric Mean Anomaly of the Sun in degrees.
private static double	getSunGeometricMeanLongitude(double julianCenturies)	Returns the Geometric Mean Longitude of the Sun.
private static double	getSunHourAngle(double latitude, double solarDeclination, double zenith, NOAACalculator.SolarEvent solarEvent)	Return the hour angle of the sun in radians at for the latitude.
private static double	getSunRiseSetUTC(Calendar calendar, double latitude, double longitude, double zenith, NOAACalculator.SolarEvent solarEvent)	Return the Universal Coordinated Time (UTC) of sunrise or sunset in minutes for the given day at the given location on earth.
private static double	getSunTrueLongitude(double julianCenturies)	Return the true longitude of the sun.
double	getUTCMidnight(Calendar calendar, GeoLocation geoLocation)	Return the Universal Coordinated Time (UTC) of the solar midnight for the end of the given civil day at the given location on earth (about 12 hours after solar noon).
double	getUTCNoon(Calendar calendar, GeoLocation geoLocation)	Return the Universal Coordinated Time (UTC) of solar noon for the given day at the given location on earth.
double	getUTCSunrise(Calendar calendar, GeoLocation geoLocation, double zenith, boolean adjustForElevation)	A method that calculates UTC sunrise as well as any time based on an angle above or below sunrise.
double	getUTCSunset(Calendar calendar, GeoLocation geoLocation, double zenith, boolean adjustForElevation)	A method that calculates UTC sunset as well as any time based on an angle above or below sunset.

Methods inherited from class com.kosherjava.zmanim.util.AstronomicalCalculator

adjustZenith, clone, getDefault, getEarthRadius, getElevationAdjustment, getRefraction, getSolarRadius, setEarthRadius, setRefraction, setSolarRadius

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

JULIAN_DAY_JAN_1_2000

private static final double JULIAN_DAY_JAN_1_2000

The Julian day of January 1, 2000, known as J2000.0.

See Also:

• Constant Field Values

JULIAN_DAYS_PER_CENTURY

private static final double JULIAN_DAYS_PER_CENTURY

Julian days per century.

See Also:

• Constant Field Values

Constructor Details

NOAACalculator

public NOAACalculator()

Default constructor of the NOAACalculator.

Method Details

getCalculatorName

public String getCalculatorName()

Description copied from class: AstronomicalCalculator

Returns the name of the algorithm.

Specified by:

getCalculatorName in class AstronomicalCalculator

Returns:

the descriptive name of the algorithm.

See Also:

• AstronomicalCalculator.getCalculatorName()

getUTCSunrise

public double getUTCSunrise(Calendar calendar,
 GeoLocation geoLocation,
 double zenith,
 boolean adjustForElevation)

Description copied from class: AstronomicalCalculator

A method that calculates UTC sunrise as well as any time based on an angle above or below sunrise. This abstract method is implemented by the classes that extend this class.

Specified by:

getUTCSunrise in class AstronomicalCalculator

Parameters:

calendar - Used to calculate day of year.

geoLocation - The location information used for astronomical calculating sun times.

zenith - the azimuth below the vertical zenith of 90 degrees. for sunrise typically the zenith used for the calculation uses geometric zenith of 90° and adjusts this slightly to account for solar refraction and the sun's radius. Another example would be AstronomicalCalendar.getBeginNauticalTwilight() that passes AstronomicalCalendar.NAUTICAL_ZENITH to this method.

adjustForElevation - Should the time be adjusted for elevation

Returns:

The UTC time of sunrise in 24-hour format. 5:45:00 AM will return 5.75.0. If an error was encountered in the calculation (expected behavior for some locations such as near the poles, Double.NaN will be returned.

See Also:

• AstronomicalCalculator.getUTCSunrise(Calendar, GeoLocation, double, boolean)

getUTCSunset

public double getUTCSunset(Calendar calendar,
 GeoLocation geoLocation,
 double zenith,
 boolean adjustForElevation)

Description copied from class: AstronomicalCalculator

A method that calculates UTC sunset as well as any time based on an angle above or below sunset. This abstract method is implemented by the classes that extend this class.

Specified by:

getUTCSunset in class AstronomicalCalculator

Parameters:

calendar - Used to calculate day of year.

geoLocation - The location information used for astronomical calculating sun times.

zenith - the azimuth below the vertical zenith of 90°. For sunset typically the zenith used for the calculation uses geometric zenith of 90° and adjusts this slightly to account for solar refraction and the sun's radius. Another example would be AstronomicalCalendar.getEndNauticalTwilight() that passes AstronomicalCalendar.NAUTICAL_ZENITH to this method.

adjustForElevation - Should the time be adjusted for elevation

Returns:

The UTC time of sunset in 24-hour format. 5:45:00 AM will return 5.75.0. If an error was encountered in the calculation (expected behavior for some locations such as near the poles, Double.NaN will be returned.

See Also:

• AstronomicalCalculator.getUTCSunset(Calendar, GeoLocation, double, boolean)

getJulianDay

private static double getJulianDay(Calendar calendar)

Return the Julian day from a Java Calendar.

Parameters:

calendar - The Java Calendar

Returns:

the Julian day corresponding to the date Note: Number is returned for the start of the Julian day. Fractional days / time should be added later.

getJulianCenturiesFromJulianDay

private static double getJulianCenturiesFromJulianDay(double julianDay)

Convert Julian day to centuries since J2000.0.

Parameters:

julianDay - the Julian Day to convert

Returns:

the centuries since 2000 Julian corresponding to the Julian Day

getSunGeometricMeanLongitude

private static double getSunGeometricMeanLongitude(double julianCenturies)

Returns the Geometric Mean Longitude of the Sun.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the Geometric Mean Longitude of the Sun in degrees

getSunGeometricMeanAnomaly

private static double getSunGeometricMeanAnomaly(double julianCenturies)

Returns the Geometric Mean Anomaly of the Sun in degrees.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the Geometric Mean Anomaly of the Sun in degrees

getEarthOrbitEccentricity

private static double getEarthOrbitEccentricity(double julianCenturies)

Return the unitless eccentricity of earth's orbit.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the unitless eccentricity

getSunEquationOfCenter

private static double getSunEquationOfCenter(double julianCenturies)

Returns the equation of center for the sun in degrees.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the equation of center for the sun in degrees

getSunTrueLongitude

private static double getSunTrueLongitude(double julianCenturies)

Return the true longitude of the sun.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the sun's true longitude in degrees

getSunApparentLongitude

private static double getSunApparentLongitude(double julianCenturies)

Return the apparent longitude of the sun.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

sun's apparent longitude in degrees

getMeanObliquityOfEcliptic

private static double getMeanObliquityOfEcliptic(double julianCenturies)

Returns the mean obliquity of the ecliptic (Axial tilt).

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the mean obliquity in degrees

getObliquityCorrection

private static double getObliquityCorrection(double julianCenturies)

Returns the corrected obliquity of the ecliptic (Axial tilt).

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the corrected obliquity in degrees

getSunDeclination

private static double getSunDeclination(double julianCenturies)

Return the declination of the sun.

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

the sun's declination in degrees

getEquationOfTime

private static double getEquationOfTime(double julianCenturies)

Return the Equation of Time - the difference between true solar time and mean solar time

Parameters:

julianCenturies - the number of Julian centuries since J2000.0.

Returns:

equation of time in minutes of time

getSunHourAngle

private static double getSunHourAngle(double latitude,
 double solarDeclination,
 double zenith,
 NOAACalculator.SolarEvent solarEvent)

Return the hour angle of the sun in radians at for the latitude.

Parameters:

latitude - the latitude of observer in degrees

solarDeclination - the declination angle of sun in degrees

zenith - the zenith

solarEvent - If the hour angle is for SUNRISE or SUNSET

Returns:

hour angle of sunrise in radians

getSolarElevation

public double getSolarElevation(Calendar calendar,
 GeoLocation geoLocation)

Description copied from class: AstronomicalCalculator

Return the Solar Elevation for the horizontal coordinate system at the given location at the given time. Can be negative if the sun is below the horizon. Not corrected for altitude.

Specified by:

getSolarElevation in class AstronomicalCalculator

Parameters:

calendar - time of calculation

geoLocation - The location information

Returns:

solar elevation in degrees. The horizon (calculated in a vacuum using the solar radius as the point) is 090°, civil twilight is -690° etc. This means that sunrise and sunset that do use refraction and are calculated from the upper limb of the sun will return about 0.83390°.

See Also:

• AstronomicalCalculator.getSolarElevation(Calendar, GeoLocation)

getSolarAzimuth

public double getSolarAzimuth(Calendar calendar,
 GeoLocation geoLocation)

Description copied from class: AstronomicalCalculator

Return the Solar Azimuth for the horizontal coordinate system at the given location at the given time. Not corrected for altitude. True south is 180 degrees.

Specified by:

getSolarAzimuth in class AstronomicalCalculator

Parameters:

calendar - time of calculation

geoLocation - The location information

Returns:

the solar azimuth in degrees. Astronomical midday would be 180 in the norther hemosphere and 0 in the southern hemosphere. Depending on the location and time of year, sunrise will have an azimuth of about 90° and sunset about 270°.

See Also:

• AstronomicalCalculator.getSolarAzimuth(Calendar, GeoLocation)

getSolarElevationAzimuth

private double getSolarElevationAzimuth(Calendar calendar,
 GeoLocation geoLocation,
 boolean isAzimuth)

Return the Solar Elevation or Solar Azimuth at the given location and time. Can be negative if the sun is below the horizon. Elevation is based on sea-level and is not adjusted for altitude.

Parameters:

calendar - time of calculation

geoLocation - The location for calculating the elevation or azimuth.

isAzimuth - true for azimuth, false for elevation

Returns:

solar elevation or azimuth in degrees.

See Also:

• getSolarElevation(Calendar, GeoLocation)
• getSolarAzimuth(Calendar, GeoLocation)

adjustHourForTimeZone

private int adjustHourForTimeZone(Calendar calendar)

Returns the hour of day adjusted for the timezone and DST. This is needed for the azimuth and elevation calculations.

Parameters:

calendar - the Calendar to extract the hour from. This must have the timezone set to the proper timezone.

Returns:

the adjusted hour corrected for timezone and DST offset.

getUTCNoon

public double getUTCNoon(Calendar calendar,
 GeoLocation geoLocation)

Return the Universal Coordinated Time (UTC) of solar noon for the given day at the given location on earth. This implementation returns true solar noon as opposed to the time halfway between sunrise and sunset. Other calculators may return a more simplified calculation of halfway between sunrise and sunset. See The Definition of Chatzos for details on solar noon calculations.

Specified by:

getUTCNoon in class AstronomicalCalculator

Parameters:

calendar - The Calendar representing the date to calculate solar noon for

geoLocation - The location information used for astronomical calculating sun times. This class uses only requires the longitude for calculating noon since it is the same time anywhere along the longitude line.

Returns:

the time in minutes from zero UTC

See Also:

• AstronomicalCalculator.getUTCNoon(Calendar, GeoLocation)
• getSolarNoonMidnightUTC(double, double, SolarEvent)

getUTCMidnight

public double getUTCMidnight(Calendar calendar,
 GeoLocation geoLocation)

Return the Universal Coordinated Time (UTC) of the solar midnight for the end of the given civil day at the given location on earth (about 12 hours after solar noon). This implementation returns true solar midnight as opposed to the time halfway between sunrise and sunset. Other calculators may return a more simplified calculation of halfway between sunrise and sunset. See The Definition of Chatzos for details on solar noon / midnight calculations.

Specified by:

getUTCMidnight in class AstronomicalCalculator

Parameters:

calendar - The Calendar representing the date to calculate solar noon for

geoLocation - The location information used for astronomical calculating sun times. This class uses only requires the longitude for calculating noon since it is the same time anywhere along the longitude line.

Returns:

the time in minutes from zero UTC

See Also:

• AstronomicalCalculator.getUTCNoon(Calendar, GeoLocation)
• getSolarNoonMidnightUTC(double, double, SolarEvent)

getSolarNoonMidnightUTC

private static double getSolarNoonMidnightUTC(double julianDay,
 double longitude,
 NOAACalculator.SolarEvent solarEvent)

Return the Universal Coordinated Time (UTC) of the current day solar noon or the the upcoming midnight (about 12 hours after solar noon) of the given day at the given location on earth.

Parameters:

julianDay - The Julian day since J2000.0.

longitude - The longitude of observer in degrees

solarEvent - If the calculation is for NOON or MIDNIGHT

Returns:

the time in minutes from zero UTC

See Also:

• AstronomicalCalculator.getUTCNoon(Calendar, GeoLocation)
• getUTCNoon(Calendar, GeoLocation)

getSunRiseSetUTC

private static double getSunRiseSetUTC(Calendar calendar,
 double latitude,
 double longitude,
 double zenith,
 NOAACalculator.SolarEvent solarEvent)

Return the Universal Coordinated Time (UTC) of sunrise or sunset in minutes for the given day at the given location on earth.

Parameters:

calendar - The calendar

latitude - The latitude of observer in degrees

longitude - Longitude of observer in degrees

zenith - Zenith

solarEvent - If the calculation is for SUNRISE or SUNSET

Returns:

the time in minutes from zero Universal Coordinated Time (UTC)

TODO:

Possibly increase the number of passes for improved accuracy, especially in the Arctic areas.