net.e175.klaus.solarpositioning

Class SPA

java.lang.Object

net.e175.klaus.solarpositioning.SPA

public final class SPA
extends Object

Calculate topocentric solar position, i.e. the location of the sun on the sky for a certain point in time on a certain point of the Earth's surface. This follows the SPA algorithm described in Reda, I.; Andreas, A. (2003): Solar Position Algorithm for Solar Radiation Applications. NREL Report No. TP-560-34302, Revised January 2008. This is not a port of the C code, but a re-implementation based on the published procedure.

Author:

Klaus Brunner

Method Summary

Modifier and Type	Method and Description
static AzimuthZenithAngle	calculateSolarPosition(GregorianCalendar date, double latitude, double longitude, double elevation, double deltaT) Calculate topocentric solar position, i.e.
static AzimuthZenithAngle	calculateSolarPosition(GregorianCalendar date, double latitude, double longitude, double elevation, double deltaT, double pressure, double temperature) Calculate topocentric solar position, i.e.
static GregorianCalendar[]	calculateSunriseTransitSet(GregorianCalendar day, double latitude, double longitude, double deltaT) Calculate the times of sunrise, sun transit (solar noon), and sunset for a given day.

Methods inherited from class java.lang.Object

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

Method Detail

calculateSolarPosition

public static AzimuthZenithAngle calculateSolarPosition(GregorianCalendar date,
                                                        double latitude,
                                                        double longitude,
                                                        double elevation,
                                                        double deltaT,
                                                        double pressure,
                                                        double temperature)

Calculate topocentric solar position, i.e. the location of the sun on the sky for a certain point in time on a certain point of the Earth's surface. This follows the SPA algorithm described in Reda, I.; Andreas, A. (2003): Solar Position Algorithm for Solar Radiation Applications. NREL Report No. TP-560-34302, Revised January 2008. The algorithm is supposed to work for the years -2000 to 6000, with uncertainties of +/-0.0003 degrees.

Parameters:

date - Observer's local date and time.

latitude - Observer's latitude, in degrees (negative south of equator).

longitude - Observer's longitude, in degrees (negative west of Greenwich).

elevation - Observer's elevation, in meters.

deltaT - Difference between earth rotation time and terrestrial time (or Universal Time and Terrestrial Time), in seconds. See http://asa.usno.navy.mil/SecK/DeltaT.html. For the year 2015, a reasonably accurate default would be 68.

pressure - Annual average local pressure, in millibars (or hectopascals). Used for refraction correction of zenith angle. If unsure, 1000 is a reasonable default.

temperature - Annual average local temperature, in degrees Celsius. Used for refraction correction of zenith angle.

Returns:

Topocentric solar position (azimuth measured eastward from north)

See Also:

AzimuthZenithAngle

calculateSolarPosition

public static AzimuthZenithAngle calculateSolarPosition(GregorianCalendar date,
                                                        double latitude,
                                                        double longitude,
                                                        double elevation,
                                                        double deltaT)

Calculate topocentric solar position, i.e. the location of the sun on the sky for a certain point in time on a certain point of the Earth's surface. This follows the SPA algorithm described in Reda, I.; Andreas, A. (2003): Solar Position Algorithm for Solar Radiation Applications. NREL Report No. TP-560-34302, Revised January 2008. The algorithm is supposed to work for the years -2000 to 6000, with uncertainties of +/-0.0003 degrees. This method does not perform refraction correction.

Parameters:

date - Observer's local date and time.

latitude - Observer's latitude, in degrees (negative south of equator).

longitude - Observer's longitude, in degrees (negative west of Greenwich).

elevation - Observer's elevation, in meters.

deltaT - Difference between earth rotation time and terrestrial time (or Universal Time and Terrestrial Time), in seconds. See http://asa.usno.navy.mil/SecK/DeltaT.html. For the year 2015, a reasonably accurate default would be 68.

Returns:

Topocentric solar position (azimuth measured eastward from north)

See Also:

AzimuthZenithAngle

calculateSunriseTransitSet

public static GregorianCalendar[] calculateSunriseTransitSet(GregorianCalendar day,
                                                             double latitude,
                                                             double longitude,
                                                             double deltaT)

Calculate the times of sunrise, sun transit (solar noon), and sunset for a given day.

Parameters:

day - GregorianCalendar of day for which sunrise/transit/sunset are to be calculated. The time of day (hour, minute, second, millisecond) is ignored.

latitude - Observer's latitude, in degrees (negative south of equator).

longitude - Observer's longitude, in degrees (negative west of Greenwich).

deltaT - Difference between earth rotation time and terrestrial time (or Universal Time and Terrestrial Time), in seconds. See http://asa.usno.navy.mil/SecK/DeltaT.html. For the year 2015, a reasonably accurate default would be 68.

Returns:

An array of 3 GregorianCalendar values corresponding to the time of sunrise, sun transit, and sunset, respectively. Note that the values for sunrise and sunset may be null: in this case, the sun stays above or below the horizon all day.