diff options
author | toma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da> | 2009-11-25 17:56:58 +0000 |
---|---|---|
committer | toma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da> | 2009-11-25 17:56:58 +0000 |
commit | ae2a03c2941bf92573f89b88ef73f8aa842bea0a (patch) | |
tree | 3566563f3fb6ac3cb3496669d8f233062d3091bc /kweather/sun.cpp | |
download | tdetoys-ae2a03c2941bf92573f89b88ef73f8aa842bea0a.tar.gz tdetoys-ae2a03c2941bf92573f89b88ef73f8aa842bea0a.zip |
Copy the KDE 3.5 branch to branches/trinity for new KDE 3.5 features.
BUG:215923
git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/kdetoys@1054174 283d02a7-25f6-0310-bc7c-ecb5cbfe19da
Diffstat (limited to 'kweather/sun.cpp')
-rw-r--r-- | kweather/sun.cpp | 462 |
1 files changed, 462 insertions, 0 deletions
diff --git a/kweather/sun.cpp b/kweather/sun.cpp new file mode 100644 index 0000000..5c6fca1 --- /dev/null +++ b/kweather/sun.cpp @@ -0,0 +1,462 @@ +/*************************************************************************** + 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; +} + |