net.time4j.calendar.astro

Enum StdSolarCalculator

java.lang.Object

java.lang.Enum<StdSolarCalculator>

net.time4j.calendar.astro.StdSolarCalculator

All Implemented Interfaces:

Serializable, Comparable<StdSolarCalculator>, SolarTime.Calculator

public enum StdSolarCalculator
extends Enum<StdSolarCalculator>
implements SolarTime.Calculator

Enumeration of some standard calculators for solar time.

Since:

3.36/4.31

Enum Constant Summary

Enum Constants

Enum Constant and Description
CC Follows closely the algorithms published by Dershowitz/Reingold in their book "Calendrical Calculations" (third edition).
NOAA Follows closely the algorithms published by NOAA (National Oceanic and Atmospheric Administration).
SIMPLE Simple and relatively fast but rather imprecise calculator.
TIME4J Based mainly on the astronomical calculations published by Jean Meeus in his book "Astronomical Algorithms" (second edition).

Method Summary

Modifier and Type	Method and Description
double	declination(double jde) Determines the declination of sun.
double	getFeature(double jde, String nameOfFeature) Supported features are at least "declination" and "right-ascension".
double	rightAscension(double jde) Determines the right ascension of sun.
static StdSolarCalculator	valueOf(String name) Returns the enum constant of this type with the specified name.
static StdSolarCalculator[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

compareTo, equals, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.time4j.calendar.astro.SolarTime.Calculator

equationOfTime, getGeodeticAngle, getZenithAngle, name, sunrise, sunset

Enum Constant Detail

SIMPLE

public static final StdSolarCalculator SIMPLE

Simple and relatively fast but rather imprecise calculator.

This calculator was once published in "Almanac for Computers, 1990 by Nautical Almanac Office in United States Naval Observatory (USNO)".

Ed Williams has used this book as the source for his algorithmic proposal. Mike Reedell has then used the proposal of Williams to realize his popular sunrise/sunset-library written in Java. Leaving aside general precision requirements, this method cannot be recommended for the polar regions. So the scope of this method is constrained to the latitudes in range -65.0 <= latitude <= +65.0 otherwise the results are expected to be unusable.

However, if users only use this method for actual years and non-polar regions, then the precision of sunrise or sunset events remain within two minutes (and the equation of time within one minute).

NOAA

public static final StdSolarCalculator NOAA

Follows closely the algorithms published by NOAA (National Oceanic and Atmospheric Administration).

Introduction

The website of NOAA also links to the calculation details. This is a calculator with reasonably good precision. But the altitude of the observer is not taken into account.

Although the precision is theoretically often better than one minute (for non-polar regions, beyond +/-72 degrees latitude rather in range of ten minutes), users should consider the fact that local topology or the actual weather conditions are not taken into account. Therefore truncating the results to minute precision should be considered.

Example

     PlainDate date = PlainDate.of(2009, 9, 6);
     SolarTime atlanta = SolarTime.ofLocation(33.766667, -84.416667, 0, StdSolarCalculator.NOAA);
     TZID tzid = () -> "America/New_York";
     assertThat(
       date.get(atlanta.sunrise())
         .get()
         .toZonalTimestamp(tzid)
         .with(PlainTime.PRECISION, ClockUnit.MINUTES),
       is(PlainTimestamp.of(2009, 9, 6, 7, 15)));
 

CC

public static final StdSolarCalculator CC

Follows closely the algorithms published by Dershowitz/Reingold in their book "Calendrical Calculations" (third edition).

The altitude of the observer is taken into account by an approximated geodetic model.

Supported features (in degrees)

• right-ascension
• declination
• mean-anomaly
• nutation
• obliquity
• solar-longitude
• lunar-longitude

TIME4J

public static final StdSolarCalculator TIME4J

Based mainly on the astronomical calculations published by Jean Meeus in his book "Astronomical Algorithms" (second edition).

Introduction

This calculation offers high precision with the general limitation that the local topology or special weather conditions cannot be calculated.

The altitude of the observer is taken into account using a spheroid (WGS84) and the assumption of a standard atmosphere (for the refraction).

Supported features (in degrees)

• right-ascension
• declination
• mean-anomaly
• nutation
• obliquity
• solar-longitude
• lunar-longitude

Method Detail

values

public static StdSolarCalculator[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (StdSolarCalculator c : StdSolarCalculator.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static StdSolarCalculator valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

declination

public double declination(double jde)

Determines the declination of sun.

Parameters:

jde - julian day in ephemeris time

Returns:

declination of sun in degrees

See Also:

rightAscension(double)

rightAscension

public double rightAscension(double jde)

Determines the right ascension of sun.

Parameters:

jde - julian day in ephemeris time

Returns:

right ascension of sun in degrees

See Also:

declination(double)

getFeature

public double getFeature(double jde,
                         String nameOfFeature)

Supported features are at least "declination" and "right-ascension".

Specified by:

getFeature in interface SolarTime.Calculator

Parameters:

jde - julian day in ephemeris time

nameOfFeature - describes what kind of value shall be calculated

Returns:

result value or Double.NaN if the feature is not supported