sunriset.h

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extern const char *timezone_name;
extern long int timezone_offset;
 
#define TMOD(x) ((x) < 0 ? (x) + 24 : ((x) >= 24 ? (x) - 24 : (x)))
#define DAYSOFF(x) ((x) < 0 ? "(-1) " : ((x) >= 24 ? "(+1) " : ""))
 
#define HOURS(h) ((int)(floor(h)))
#define MINUTES(h) ((int)(60 * (h - floor(h))))
 
#ifndef ABS
#    define ABS(x) ((x) < 0 ? -(x) : (x))
#endif
 
/* A macro to compute the number of days elapsed since 2000 Jan 0.0 */
/* (which is equal to 1999 Dec 31, 0h UT)                           */
/* Dan R sez: This is some pretty fucking high magic. */
#define days_since_2000_Jan_0(y, m, d)                                                                                 \
    (367L * (y) - ((7 * ((y) + (((m) + 9) / 12))) / 4) + ((275 * (m)) / 9) + (d) - 730530L)
 
/* Some conversion factors between radians and degrees */
 
#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.                         */
 
/* This macro computes the length of the day, from sunrise to sunset. */
/* Sunrise/set is considered to occur when the Sun's upper limb is    */
/* 50 arc minutes below the horizon (this accounts for the refraction */
/* of the Earth's atmosphere).                                        */
/* The original version of the program used the value of 35 arc mins, */
/* which is the accepted value in Sweden.                             */
#define day_length(year, month, day, lon, lat) __daylen__(year, month, day, lon, lat, -50.0 / 60.0, 1)
 
/* This macro computes the length of the day, including civil twilight. */
/* Civil twilight starts/ends when the Sun's center is 6 degrees below  */
/* the horizon.                                                         */
#define day_civil_twilight_length(year, month, day, lon, lat) __daylen__(year, month, day, lon, lat, -6.0, 0)
 
/* This macro computes the length of the day, incl. nautical twilight.  */
/* Nautical twilight starts/ends when the Sun's center is 12 degrees    */
/* below the horizon.                                                   */
#define day_nautical_twilight_length(year, month, day, lon, lat) __daylen__(year, month, day, lon, lat, -12.0, 0)
 
/* This macro computes the length of the day, incl. astronomical twilight. */
/* Astronomical twilight starts/ends when the Sun's center is 18 degrees   */
/* below the horizon.                                                      */
#define day_astronomical_twilight_length(year, month, day, lon, lat) __daylen__(year, month, day, lon, lat, -18.0, 0)
 
/* This macro 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).                                        */
#define sun_rise_set(year, month, day, lon, lat, rise, set)                                                            \
    __sunriset__(year, month, day, lon, lat, -35.0 / 60.0, 1, rise, set)
 
/* This macro computes the start and end times of civil twilight.       */
/* Civil twilight starts/ends when the Sun's center is 6 degrees below  */
/* the horizon.                                                         */
#define civil_twilight(year, month, day, lon, lat, start, end)                                                         \
    __sunriset__(year, month, day, lon, lat, -6.0, 0, start, end)
 
/* This macro computes the start and end times of nautical twilight.    */
/* Nautical twilight starts/ends when the Sun's center is 12 degrees    */
/* below the horizon.                                                   */
#define nautical_twilight(year, month, day, lon, lat, start, end)                                                      \
    __sunriset__(year, month, day, lon, lat, -12.0, 0, start, end)
 
/* This macro computes the start and end times of astronomical twilight.   */
/* Astronomical twilight starts/ends when the Sun's center is 18 degrees   */
/* below the horizon.                                                      */
#define astronomical_twilight(year, month, day, lon, lat, start, end)                                                  \
    __sunriset__(year, month, day, lon, lat, -18.0, 0, start, end)
 
/* Function prototypes */
 
double __daylen__(int year, int month, int day, double lon, double lat, double altit, int upper_limb);
 
int __sunriset__(int year, int month, int day, double lon, double lat, double altit, int upper_limb, double *rise,
                 double *set);
 
void sunpos(double d, double *lon, double *r);
 
void sun_RA_dec(double d, double *RA, double *dec, double *r);
 
double revolution(double x);
 
double rev180(double x);
 
double GMST0(double d);