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+/***************************************************************************
+ sun.cpp - Sun Rise and Set Calculations
+ -------------------
+ begin : Friday July 11 2003
+ copyright : (C) 2003 by John Ratke
+ email : jratke@comcast.net
+
+ history:
+ Written as DAYLEN.C, 1989-08-16
+ Modified to SUNRISET.C, 1992-12-01
+ (c) Paul Schlyter, 1989, 1992
+ Released to the public domain by Paul Schlyter, December 1992
+ Portions Modified to SUNDOWN.NLM by Cliff Haas 98-05-22
+ Converted to C++ and modified by John Ratke
+
+***************************************************************************/
+
+/***************************************************************************
+* *
+* This program is free software; you can redistribute it and/or modify *
+* it under the terms of the GNU General Public License as published by *
+* the Free Software Foundation; either version 2 of the License, or *
+* (at your option) any later version. *
+* *
+***************************************************************************/
+
+#include <kdebug.h>
+
+#include <math.h>
+#include "sun.h"
+
+/* A function to compute the number of days elapsed since 2000 Jan 0.0 */
+/* (which is equal to 1999 Dec 31, 0h UT) */
+
+static inline double days_since_2000_Jan_0(int y, int m, int d)
+{
+ return (367L*(y)-((7*((y)+(((m)+9)/12)))/4)+((275*(m))/9)+(d)-730530L);
+}
+
+/* Some conversion factors between radians and degrees */
+
+static const double PI = 3.14159265358979323846;
+
+static const double RADEG = ( 180.0 / PI );
+static const double DEGRAD = ( PI / 180.0 );
+
+/* The trigonometric functions in degrees */
+static inline double sind(double x) { return sin( x * DEGRAD ); }
+static inline double cosd(double x) { return cos( x * DEGRAD ); }
+static inline double tand(double x) { return tan( x * DEGRAD ); }
+static inline double atand(double x) { return RADEG * atan(x); }
+static inline double asind(double x) { return RADEG * asin(x); }
+static inline double acosd(double x) { return RADEG * acos(x); }
+static inline double atan2d(double y, double x) { return RADEG * atan2(y, x); }
+
+/* Other local functions */
+static double latitudeToDouble( const QString &latitude );
+static double longitudeToDouble( const QString &longitude );
+static int __sunriset__( int year, int month, int day, double lon, double lat,
+ double altit, int upper_limb, double &trise, double &tset );
+static void sunpos( double d, double &lon, double &r );
+static void sun_RA_dec( double d, double &RA, double &dec, double &r );
+static inline double revolution( const double x );
+static inline double rev180( const double x );
+static inline double GMST0( const double d );
+
+
+/*
+ * This function computes times for sunrise/sunset.
+ * Sunrise/set is considered to occur when the Sun's upper limb is
+ * 35 arc minutes below the horizon (this accounts for the refraction
+ * of the Earth's atmosphere).
+ */
+static inline int sun_rise_set(int year, int month, int day, double lon, double lat, double &rise, double &set)
+{
+ return __sunriset__( year, month, day, lon, lat, -35.0/60.0, 1, rise, set );
+}
+
+/*
+ * This function computes the start and end times of civil twilight.
+ * Civil twilight starts/ends when the Sun's center is 6 degrees below
+ * the horizon.
+ */
+static inline int civil_twilight(int year, int month, int day, double lon, double lat, double &start, double &end)
+{
+ return __sunriset__( year, month, day, lon, lat, -6.0, 0, start, end );
+}
+
+
+Sun::Sun(const QString &latitude, const QString &longitude, QDate date, const int localUTCOffset) :
+ m_date(date),
+ m_lat(latitudeToDouble(latitude)), m_lon(longitudeToDouble(longitude)),
+ m_localUTCOffset(localUTCOffset)
+{
+}
+
+
+QTime Sun::computeRiseTime()
+{
+ double riseTime;
+ double setTime;
+
+ sun_rise_set( m_date.year(), m_date.month(), m_date.day(), m_lon, m_lat, riseTime, setTime );
+
+ QTime result = convertDoubleToLocalTime( riseTime );
+
+ if ( ! result.isValid() )
+ result.setHMS( 6, 0, 0 );
+
+ return result;
+}
+
+
+QTime Sun::computeSetTime()
+{
+ double riseTime;
+ double setTime;
+
+ sun_rise_set( m_date.year(), m_date.month(), m_date.day(), m_lon, m_lat, riseTime, setTime );
+
+ QTime result = convertDoubleToLocalTime( setTime );
+
+ if ( ! result.isValid() )
+ result.setHMS( 19, 0, 0 );
+
+ return result;
+}
+
+
+QTime Sun::computeCivilTwilightStart()
+{
+ double start;
+ double end;
+
+ civil_twilight( m_date.year(), m_date.month(), m_date.day(), m_lon, m_lat, start, end );
+
+ QTime result = convertDoubleToLocalTime( start );
+
+ if ( ! result.isValid() )
+ result.setHMS( 6, 0, 0 );
+
+ return result;
+}
+
+
+QTime Sun::computeCivilTwilightEnd()
+{
+ double start;
+ double end;
+
+ civil_twilight( m_date.year(), m_date.month(), m_date.day(), m_lon, m_lat, start, end );
+
+ QTime result = convertDoubleToLocalTime( end );
+
+ if ( ! result.isValid() )
+ result.setHMS( 19, 0, 0 );
+
+ return result;
+}
+
+
+/*
+ * Converts latitude in format DD-MMH, where DD is degrees, MM is minutes,
+ * and H is Hemisphere (N for North, or S for South) to a floating point number.
+ *
+ * For example: 27-00S to -27.0
+ *
+ * Does not currently handle seconds.
+ */
+static double latitudeToDouble( const QString &latitude )
+{
+ double result;
+
+ double dd = latitude.left(2).toDouble();
+ double mm = latitude.mid(3, 2).toDouble();
+
+ result = dd + (mm / 60);
+
+ if (latitude.contains("S"))
+ result *= -1;
+
+ return result;
+}
+
+
+static double longitudeToDouble( const QString &longitude )
+{
+ double result;
+
+ double ddd = longitude.left(3).toDouble();
+ double mm = longitude.mid(4, 2).toDouble();
+
+ result = ddd + (mm / 60);
+
+ if (longitude.contains("W"))
+ result *= -1;
+
+ return result;
+}
+
+
+QTime Sun::convertDoubleToLocalTime( const double time )
+{
+ QTime result;
+
+ // Example: say time is 17.7543 Then hours = 17 and minutes = 0.7543 * 60 = 45.258
+ // We need to convert the time to CORRECT local hours
+ int hours = (int)floor(time);
+ int localhours = hours + (m_localUTCOffset / 60);
+
+ // We need to convert the time to CORRECT local minutes
+ int minutes = (int)floor((time - hours) * 60);
+ int localminutes = minutes + (m_localUTCOffset % 60);
+
+ // We now have to adjust the time to be within the 60m boundary
+ if (localminutes < 0)
+ {
+ //As minutes is less than 0, we need to
+ //reduce a hour and add 60m to minutes.
+ localminutes += 60;
+ localhours--;
+ }
+ if (localminutes >= 60)
+ {
+ //As minutes are more than 60, we need to
+ //add one more hour and reduce the minutes to
+ //a value between 0 and 59.
+ localminutes -= 60;
+ localhours++;
+ }
+
+ // Round up or down to nearest second.
+ // Use rint instead of nearbyint because rint is in FreeBSD
+ int seconds = (int)rint( fabs( minutes - ((time - hours) * 60) ) * 60 );
+
+ // We now have to adjust the time to be within the 24h boundary
+ if (localhours < 0) { localhours += 24; }
+ if (localhours >= 24) { localhours -= 24; }
+
+ // Try to set the hours, minutes and seconds for the local time.
+ // If this doesn't work, then we will return the invalid time.
+ result.setHMS( localhours, localminutes, seconds );
+
+ return result;
+}
+
+
+/*
+ * Note: year,month,date = calendar date, 1801-2099 only.
+ * Eastern longitude positive, Western longitude negative
+ * Northern latitude positive, Southern latitude negative
+ * The longitude value IS critical in this function!
+ * altit = the altitude which the Sun should cross
+ * Set to -35/60 degrees for rise/set, -6 degrees
+ * for civil, -12 degrees for nautical and -18
+ * degrees for astronomical twilight.
+ * upper_limb: non-zero -> upper limb, zero -> center
+ * Set to non-zero (e.g. 1) when computing rise/set
+ * times, and to zero when computing start/end of
+ * twilight.
+ * trise = the rise time gets stored here
+ * tset = the set time gets stored here
+ * Both times are relative to the specified altitude,
+ * and thus this function can be used to comupte
+ * various twilight times, as well as rise/set times
+ *
+ * Return value: 0 = sun rises/sets this day, times stored in
+ * trise and tset.
+ * +1 = sun above the specified "horizon" 24 hours.
+ * trise set to time when the sun is at south,
+ * minus 12 hours while tset is set to the south
+ * time plus 12 hours. "Day" length = 24 hours
+ * -1 = sun is below the specified "horizon" 24 hours
+ * "Day" length = 0 hours, trise and tset are
+ * both set to the time when the sun is at south.
+ *
+ */
+static int __sunriset__( int year, int month, int day, double lon, double lat,
+ double altit, int upper_limb, double &trise, double &tset )
+{
+ double d; /* Days since 2000 Jan 0.0 (negative before) */
+ double sr; /* Solar distance, astronomical units */
+ double sRA; /* Sun's Right Ascension */
+ double sdec; /* Sun's declination */
+ double sradius; /* Sun's apparent radius */
+ double t; /* Diurnal arc */
+ double tsouth; /* Time when Sun is at south */
+ double sidtime; /* Local sidereal time */
+
+ int rc = 0; /* Return code from function - usually 0 */
+
+ /* Compute d of 12h local mean solar time */
+ d = days_since_2000_Jan_0(year, month, day);
+
+ d = days_since_2000_Jan_0(year, month, day) + 0.5 - lon / 360.0;
+
+ /* Compute local sideral time of this moment */
+ sidtime = revolution( GMST0(d) + 180.0 + lon );
+
+ /* Compute Sun's RA + Decl at this moment */
+ sun_RA_dec( d, sRA, sdec, sr );
+
+ /* Compute time when Sun is at south - in hours UT */
+ tsouth = 12.0 - rev180(sidtime - sRA) / 15.0;
+
+ /* Compute the Sun's apparent radius, degrees */
+ sradius = 0.2666 / sr;
+
+ /* Do correction to upper limb, if necessary */
+ if ( upper_limb )
+ altit -= sradius;
+
+ /* Compute the diurnal arc that the Sun traverses to reach */
+ /* the specified altitide altit: */
+ double cost;
+ cost = ( sind(altit) - sind(lat) * sind(sdec) ) /
+ ( cosd(lat) * cosd(sdec) );
+ if ( cost >= 1.0 )
+ {
+ rc = -1;
+ t = 0.0; /* Sun always below altit */
+ }
+ else if ( cost <= -1.0 )
+ {
+ rc = +1;
+ t = 12.0; /* Sun always above altit */
+ }
+ else
+ t = acosd(cost) / 15.0; /* The diurnal arc, hours */
+
+ /* Store rise and set times - in hours UT */
+ trise = tsouth - t;
+ tset = tsouth + t;
+
+ return rc;
+}
+
+
+/* This function computes the Sun's position at any instant
+ *
+ * Computes the Sun's ecliptic longitude and distance
+ * at an instant given in d, number of days since
+ * 2000 Jan 0.0. The Sun's ecliptic latitude is not
+ * computed, since it's always very near 0.
+ */
+static void sunpos( double d, double &lon, double &r )
+{
+ double M; /* Mean anomaly of the Sun */
+ double w; /* Mean longitude of perihelion */
+ /* Note: Sun's mean longitude = M + w */
+ double e; /* Eccentricity of Earth's orbit */
+ double E; /* Eccentric anomaly */
+ double x;
+ double y; /* x, y coordinates in orbit */
+ double v; /* True anomaly */
+
+ /* Compute mean elements */
+ M = revolution( 356.0470 + 0.9856002585 * d );
+ w = 282.9404 + 4.70935E-5 * d;
+ e = 0.016709 - 1.151E-9 * d;
+
+ /* Compute true longitude and radius vector */
+ E = M + e * RADEG * sind(M) * ( 1.0 + e * cosd(M) );
+ x = cosd(E) - e;
+ y = sqrt( 1.0 - e*e ) * sind(E);
+ r = sqrt( x*x + y*y ); /* Solar distance */
+ v = atan2d( y, x ); /* True anomaly */
+ lon = v + w; /* True solar longitude */
+
+ if ( lon >= 360.0 )
+ lon -= 360.0; /* Make it 0..360 degrees */
+}
+
+
+static void sun_RA_dec( double d, double &RA, double &dec, double &r )
+{
+ double lon;
+ double obl_ecl;
+ double x;
+ double y;
+ double z;
+
+ /* Compute Sun's ecliptical coordinates */
+ sunpos( d, lon, r );
+
+ /* Compute ecliptic rectangular coordinates (z=0) */
+ x = r * cosd(lon);
+ y = r * sind(lon);
+
+ /* Compute obliquity of ecliptic (inclination of Earth's axis) */
+ obl_ecl = 23.4393 - 3.563E-7 * d;
+
+ /* Convert to equatorial rectangular coordinates - x is unchanged */
+ z = y * sind(obl_ecl);
+ y = y * cosd(obl_ecl);
+
+ /* Convert to spherical coordinates */
+ RA = atan2d( y, x );
+ dec = atan2d( z, sqrt(x*x + y*y) );
+}
+
+
+static const double INV360 = 1.0 / 360.0;
+
+/*
+ * This function reduces any angle to within the first revolution
+ * by subtracting or adding even multiples of 360.0 until the
+ * result is >= 0.0 and < 360.0
+ */
+static inline double revolution( const double x )
+{
+ return ( x - 360.0 * floor( x * INV360 ) );
+}
+
+/*
+ * Reduce angle to within +180..+180 degrees
+ */
+static inline double rev180( const double x )
+{
+ return ( x - 360.0 * floor( x * INV360 + 0.5 ) );
+}
+
+
+/*
+ * This function computes GMST0, the Greenwhich Mean Sidereal Time
+ * at 0h UT (i.e. the sidereal time at the Greenwhich meridian at
+ * 0h UT). GMST is then the sidereal time at Greenwich at any
+ * time of the day. I've generelized GMST0 as well, and define it
+ * as: GMST0 = GMST - UT -- this allows GMST0 to be computed at
+ * other times than 0h UT as well. While this sounds somewhat
+ * contradictory, it is very practical: instead of computing
+ * GMST like:
+ *
+ * GMST = (GMST0) + UT * (366.2422/365.2422)
+ *
+ * where (GMST0) is the GMST last time UT was 0 hours, one simply
+ * computes:
+ *
+ * GMST = GMST0 + UT
+ *
+ * where GMST0 is the GMST "at 0h UT" but at the current moment!
+ * Defined in this way, GMST0 will increase with about 4 min a
+ * day. It also happens that GMST0 (in degrees, 1 hr = 15 degr)
+ * is equal to the Sun's mean longitude plus/minus 180 degrees!
+ * (if we neglect aberration, which amounts to 20 seconds of arc
+ * or 1.33 seconds of time)
+ *
+ */
+static inline double GMST0( const double d )
+{
+ double sidtim0;
+
+ /* Sidtime at 0h UT = L (Sun's mean longitude) + 180.0 degr */
+ /* L = M + w, as defined in sunpos(). Since I'm too lazy to */
+ /* add these numbers, I'll let the C compiler do it for me. */
+ /* Any decent C compiler will add the constants at compile */
+ /* time, imposing no runtime or code overhead. */
+ sidtim0 = revolution( ( 180.0 + 356.0470 + 282.9404 ) +
+ ( 0.9856002585 + 4.70935E-5 ) * d );
+ return sidtim0;
+}
+
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