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

  • Field Details

  • 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:

    • 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:

    • 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:

    • 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 start of day. Fractional days 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 static double getSolarElevation(Calendar calendar, double latitude, double longitude)
      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.
      Parameters:
      calendar - time of calculation
      latitude - latitude of location for calculation
      longitude - longitude of location for calculation
      Returns:
      solar elevation in degrees - horizon is 0 degrees, civil twilight is -6 degrees

    • getSolarAzimuth

      public static double getSolarAzimuth(Calendar calendar, double latitude, double longitude)
      Return the Solar Azimuth for the horizontal coordinate system at the given location at the given time. Not corrected for altitude. True south is 0 degrees.
      Parameters:
      calendar - time of calculation
      latitude - latitude of location for calculation
      longitude - longitude of location for calculation
      Returns:
      the solar azimuth

    • 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:

    • 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:

    • 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:

    • 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.