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Diffstat (limited to 'ext/date/lib/astro.c')
| -rw-r--r-- | ext/date/lib/astro.c | 303 |
1 files changed, 303 insertions, 0 deletions
diff --git a/ext/date/lib/astro.c b/ext/date/lib/astro.c new file mode 100644 index 0000000..d770d1a --- /dev/null +++ b/ext/date/lib/astro.c @@ -0,0 +1,303 @@ +/* + +----------------------------------------------------------------------+ + | PHP Version 5 | + +----------------------------------------------------------------------+ + | Copyright (c) 1997-2013 The PHP Group | + +----------------------------------------------------------------------+ + | This source file is subject to version 3.01 of the PHP license, | + | that is bundled with this package in the file LICENSE, and is | + | available through the world-wide-web at the following url: | + | http://www.php.net/license/3_01.txt | + | If you did not receive a copy of the PHP license and are unable to | + | obtain it through the world-wide-web, please send a note to | + | license@php.net so we can mail you a copy immediately. | + +----------------------------------------------------------------------+ + | Algorithms are taken from a public domain source by Paul | + | Schlyter, who wrote this in December 1992 | + +----------------------------------------------------------------------+ + | Authors: Derick Rethans <derick@derickrethans.nl> | + +----------------------------------------------------------------------+ + */ + +/* $Id$ */ + +#include <stdio.h> +#include <math.h> +#include "timelib.h" + +#define days_since_2000_Jan_0(y,m,d) \ + (367L*(y)-((7*((y)+(((m)+9)/12)))/4)+((275*(m))/9)+(d)-730530L) + +#ifndef PI + #define PI 3.1415926535897932384 +#endif + +#define RADEG ( 180.0 / PI ) +#define DEGRAD ( PI / 180.0 ) + +/* The trigonometric functions in degrees */ + +#define sind(x) sin((x)*DEGRAD) +#define cosd(x) cos((x)*DEGRAD) +#define tand(x) tan((x)*DEGRAD) + +#define atand(x) (RADEG*atan(x)) +#define asind(x) (RADEG*asin(x)) +#define acosd(x) (RADEG*acos(x)) +#define atan2d(y,x) (RADEG*atan2(y,x)) + + +/* Following are some macros around the "workhorse" function __daylen__ */ +/* They mainly fill in the desired values for the reference altitude */ +/* below the horizon, and also selects whether this altitude should */ +/* refer to the Sun's center or its upper limb. */ + + +#include "astro.h" + +/******************************************************************/ +/* 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 */ +/******************************************************************/ + +#define INV360 (1.0 / 360.0) + +/*****************************************/ +/* Reduce angle to within 0..360 degrees */ +/*****************************************/ +static double astro_revolution(double x) +{ + return (x - 360.0 * floor(x * INV360)); +} + +/*********************************************/ +/* Reduce angle to within +180..+180 degrees */ +/*********************************************/ +static double astro_rev180( double x ) +{ + return (x - 360.0 * floor(x * INV360 + 0.5)); +} + +/*******************************************************************/ +/* This function computes GMST0, the Greenwich 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 generalized 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 double astro_GMST0(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 = astro_revolution((180.0 + 356.0470 + 282.9404) + (0.9856002585 + 4.70935E-5) * d); + return sidtim0; +} + +/* 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 astro_sunpos(double d, double *lon, double *r) +{ + double M, /* Mean anomaly of the Sun */ + w, /* Mean longitude of perihelion */ + /* Note: Sun's mean longitude = M + w */ + e, /* Eccentricity of Earth's orbit */ + E, /* Eccentric anomaly */ + x, y, /* x, y coordinates in orbit */ + v; /* True anomaly */ + + /* Compute mean elements */ + M = astro_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 astro_sun_RA_dec(double d, double *RA, double *dec, double *r) +{ + double lon, obl_ecl, x, y, z; + + /* Compute Sun's ecliptical coordinates */ + astro_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)); +} + +/** + * Note: timestamp = unixtimestamp (NEEDS to be 00:00:00 UT) + * 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. + * *rise = where to store the rise time + * *set = where to store the set time + * Both times are relative to the specified altitude, + * and thus this function can be used to compute + * various twilight times, as well as rise/set times + * Return value: 0 = sun rises/sets this day, times stored at + * *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. + * + */ +int timelib_astro_rise_set_altitude(timelib_time *t_loc, double lon, double lat, double altit, int upper_limb, double *h_rise, double *h_set, timelib_sll *ts_rise, timelib_sll *ts_set, timelib_sll *ts_transit) +{ + double d, /* Days since 2000 Jan 0.0 (negative before) */ + sr, /* Solar distance, astronomical units */ + sRA, /* Sun's Right Ascension */ + sdec, /* Sun's declination */ + sradius, /* Sun's apparent radius */ + t, /* Diurnal arc */ + tsouth, /* Time when Sun is at south */ + sidtime; /* Local sidereal time */ + timelib_time *t_utc; + timelib_sll timestamp, old_sse; + + int rc = 0; /* Return cde from function - usually 0 */ + + /* Normalize time */ + old_sse = t_loc->sse; + t_loc->h = 12; + t_loc->i = t_loc->s = 0; + timelib_update_ts(t_loc, NULL); + + /* Calculate TS belonging to UTC 00:00 of the current day */ + t_utc = timelib_time_ctor(); + t_utc->y = t_loc->y; + t_utc->m = t_loc->m; + t_utc->d = t_loc->d; + t_utc->h = t_utc->i = t_utc->s = 0; + timelib_update_ts(t_utc, NULL); + + /* Compute d of 12h local mean solar time */ + timestamp = t_loc->sse; + d = timelib_ts_to_juliandate(timestamp) - lon/360.0; + + /* Compute local sidereal time of this moment */ + sidtime = astro_revolution(astro_GMST0(d) + 180.0 + lon); + + /* Compute Sun's RA + Decl at this moment */ + astro_sun_RA_dec( d, &sRA, &sdec, &sr ); + + /* Compute time when Sun is at south - in hours UT */ + tsouth = 12.0 - astro_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 altitude altit: */ + { + double cost; + cost = (sind(altit) - sind(lat) * sind(sdec)) / (cosd(lat) * cosd(sdec)); + *ts_transit = t_utc->sse + (tsouth * 3600); + if (cost >= 1.0) { + rc = -1; + t = 0.0; /* Sun always below altit */ + + *ts_rise = *ts_set = t_utc->sse + (tsouth * 3600); + } else if (cost <= -1.0) { + rc = +1; + t = 12.0; /* Sun always above altit */ + + *ts_rise = t_loc->sse - (12 * 3600); + *ts_set = t_loc->sse + (12 * 3600); + } else { + t = acosd(cost) / 15.0; /* The diurnal arc, hours */ + + /* Store rise and set times - as Unix Timestamp */ + *ts_rise = ((tsouth - t) * 3600) + t_utc->sse; + *ts_set = ((tsouth + t) * 3600) + t_utc->sse; + + *h_rise = (tsouth - t); + *h_set = (tsouth + t); + } + } + + /* Kill temporary time and restore original sse */ + timelib_time_dtor(t_utc); + t_loc->sse = old_sse; + + return rc; +} + +double timelib_ts_to_juliandate(timelib_sll ts) +{ + double tmp; + + tmp = ts; + tmp /= 86400; + tmp += 2440587.5; + tmp -= 2451543; + + return tmp; +} |