diff options
Diffstat (limited to 'solar.c')
| -rw-r--r-- | solar.c | 188 |
1 files changed, 94 insertions, 94 deletions
@@ -41,23 +41,23 @@ julian_centuries(double *nowp) /** * Convert a Julian Centuries timestamp to a Julian Day timestamp * - * @param tm The time in Julian Centuries + * @param t The time in Julian Centuries * @return The time in Julian Days */ -static inline double -julian_centuries_to_julian_day(double tm) +static double +julian_centuries_to_julian_day(double t) { - return tm * 36525.0 + 2451545.0; + return 36525.0 * t + 2451545.0; } /** * Convert an angle (or otherwise) from degrees to radians * - * @param deg The angle in degrees. - * @param The angle in radians. + * @param deg The angle in degrees + * @param The angle in radians */ -static inline double +static double radians(double deg) { return deg * (double)M_PI / 180.0; @@ -66,10 +66,10 @@ radians(double deg) /** * Convert an angle (or otherwise) from radians to degrees * - * @param rad The angle in radians. - * @param The angle in degrees. + * @param rad The angle in radians + * @param The angle in degrees */ -static inline double +static double degrees(double rad) { return rad * 180.0 / (double)M_PI; @@ -79,170 +79,170 @@ degrees(double rad) /** * Calculates the Sun's elevation from the solar hour angle * - * @param longitude The longitude in degrees eastwards - * from Greenwich, negative for westwards + * @param latitude The latitude in degrees northwards from + * the equator, negative for southwards * @param declination The declination, in radians * @param hour_angle The solar hour angle, in radians * @return The Sun's elevation, in radians */ -static inline double +static double elevation_from_hour_angle(double latitude, double declination, double hour_angle) { - double rc = cos(radians(latitude)); - rc *= cos(hour_angle) * cos(declination); - rc += sin(radians(latitude)) * sin(declination); - return asin(rc); + double r = cos(radians(latitude)); + r *= cos(hour_angle) * cos(declination); + r += sin(radians(latitude)) * sin(declination); + return asin(r); } /** * Calculates the Sun's geometric mean longitude * - * @param tm The time in Julian Centuries - * @return The Sun's geometric mean longitude in radians + * @param t The time in Julian Centuries + * @return The Sun's geometric mean longitude in radians */ -static inline double -sun_geometric_mean_longitude(double tm) +static double +sun_geometric_mean_longitude(double t) { - double rc = fmod(pow(0.0003032 * tm, 2.0) + 36000.76983 * tm + 280.46646, 360.0); + double r = fmod(pow(0.0003032 * t, 2.0) + 36000.76983 * t + 280.46646, 360.0); #if defined(TIMETRAVELLER) - rc = rc < 0.0 ? (rc + 360.0) : rc; + r = r < 0.0 ? (r + 360.0) : r; #endif - return radians(rc); + return radians(r); } /** * Calculates the Sun's geometric mean anomaly * - * @param tm The time in Julian Centuries - * @return The Sun's geometric mean anomaly in radians + * @param t The time in Julian Centuries + * @return The Sun's geometric mean anomaly in radians */ -static inline double -sun_geometric_mean_anomaly(double tm) +static double +sun_geometric_mean_anomaly(double t) { - return radians(pow(-0.0001537 * tm, 2.0) + 35999.05029 * tm + 357.52911); + return radians(pow(-0.0001537 * t, 2.0) + 35999.05029 * t + 357.52911); } /** * Calculates the Earth's orbit eccentricity * - * @param tm The time in Julian Centuries - * @return The Earth's orbit eccentricity + * @param t The time in Julian Centuries + * @return The Earth's orbit eccentricity */ -static inline double -earth_orbit_eccentricity(double tm) +static double +earth_orbit_eccentricity(double t) { - return pow(-0.0000001267 * tm, 2.0) - 0.000042037 * tm + 0.016708634; + return pow(-0.0000001267 * t, 2.0) - 0.000042037 * t + 0.016708634; } /** * Calculates the Sun's equation of the centre, the difference * between the true anomaly and the mean anomaly * - * @param tm The time in Julian Centuries - * @return The Sun's equation of the centre, in radians + * @param t The time in Julian Centuries + * @return The Sun's equation of the centre, in radians */ -static inline double -sun_equation_of_centre(double tm) +static double +sun_equation_of_centre(double t) { - double a = sun_geometric_mean_anomaly(tm), rc; - rc = sin(1.0 * a) * (pow(-0.000014 * tm, 2.0) - 0.004817 * tm + 1.914602); - rc += sin(2.0 * a) * (-0.000101 * tm + 0.019993); - rc += sin(3.0 * a) * 0.000289; - return radians(rc); + double a = sun_geometric_mean_anomaly(t), r; + r = sin(1.0 * a) * (pow(-0.000014 * t, 2.0) - 0.004817 * t + 1.914602); + r += sin(2.0 * a) * (-0.000101 * t + 0.019993); + r += sin(3.0 * a) * 0.000289; + return radians(r); } /** * Calculates the Sun's real longitudinal position * - * @param tm The time in Julian Centuries - * @return The longitude, in radians + * @param t The time in Julian Centuries + * @return The longitude, in radians */ -static inline double -sun_real_longitude(double tm) +static double +sun_real_longitude(double t) { - return sun_geometric_mean_longitude(tm) + sun_equation_of_centre(tm); + return sun_geometric_mean_longitude(t) + sun_equation_of_centre(t); } /** * Calculates the Sun's apparent longitudinal position * - * @param tm The time in Julian Centuries - * @return The longitude, in radians + * @param t The time in Julian Centuries + * @return The longitude, in radians */ -static inline double -sun_apparent_longitude(double tm) +static double +sun_apparent_longitude(double t) { - double rc = degrees(sun_real_longitude(tm)) - 0.00569; - return radians(rc - 0.00478 * sin(radians(-1934.136 * tm + 125.04))); + double r = degrees(sun_real_longitude(t)) - 0.00569; + return radians(r - 0.00478 * sin(radians(-1934.136 * t + 125.04))); } /** * Calculates the mean ecliptic obliquity of the Sun's * apparent motion without variation correction * - * @param tm The time in Julian Centuries - * @return The uncorrected mean obliquity, in radians + * @param t The time in Julian Centuries + * @return The uncorrected mean obliquity, in radians */ static double -mean_ecliptic_obliquity(double tm) +mean_ecliptic_obliquity(double t) { - double rc = pow(0.001813 * tm, 3.0) - pow(0.00059 * tm, 2.0) - 46.815 * tm + 21.448; - return radians(23.0 + (26.0 + rc / 60.0) / 60.0); + double r = pow(0.001813 * t, 3.0) - pow(0.00059 * t, 2.0) - 46.815 * t + 21.448; + return radians(23.0 + (26.0 + r / 60.0) / 60.0); } /** * Calculates the mean ecliptic obliquity of the Sun's * parent motion with variation correction * - * @param tm The time in Julian Centuries - * @return The mean obliquity, in radians + * @param t The time in Julian Centuries + * @return The mean obliquity, in radians */ static double -corrected_mean_ecliptic_obliquity(double tm) +corrected_mean_ecliptic_obliquity(double t) { - double rc = 0.00256 * cos(radians(-1934.136 * tm + 125.04)); - return radians(rc + degrees(mean_ecliptic_obliquity(tm))); + double r = 0.00256 * cos(radians(-1934.136 * t + 125.04)); + return radians(r + degrees(mean_ecliptic_obliquity(t))); } /** * Calculates the Sun's declination * - * @param tm The time in Julian Centuries - * @return The Sun's declination, in radian + * @param t The time in Julian Centuries + * @return The Sun's declination, in radian */ -static inline double -solar_declination(double tm) +static double +solar_declination(double t) { - double rc = sin(corrected_mean_ecliptic_obliquity(tm)); - return asin(rc * sin(sun_apparent_longitude(tm))); + double r = sin(corrected_mean_ecliptic_obliquity(t)); + return asin(r * sin(sun_apparent_longitude(t))); } /** * Calculates the equation of time, the discrepancy * between apparent and mean solar time * - * @param tm The time in Julian Centuries - * @return The equation of time, in degrees + * @param t The time in Julian Centuries + * @return The equation of time, in degrees */ -static inline double -equation_of_time(double tm) +static double +equation_of_time(double t) { - double l = sun_geometric_mean_longitude(tm); - double e = earth_orbit_eccentricity(tm); - double m = sun_geometric_mean_anomaly(tm); - double y = pow(tan(corrected_mean_ecliptic_obliquity(tm) / 2.0), 2.0); - double rc = y * sin(2.0 * l); - rc += (4.0 * y * cos(2.0 * l) - 2.0) * e * sin(m); - rc -= pow(0.5 * y, 2.0) * sin(4.0 * l); - rc -= pow(1.25 * e, 2.0) * sin(2.0 * m); - return 4.0 * degrees(rc); + double l = sun_geometric_mean_longitude(t); + double e = earth_orbit_eccentricity(t); + double m = sun_geometric_mean_anomaly(t); + double y = pow(tan(corrected_mean_ecliptic_obliquity(t) / 2.0), 2.0); + double r = y * sin(2.0 * l); + r += (4.0 * y * cos(2.0 * l) - 2.0) * e * sin(m); + r -= pow(0.5 * y, 2.0) * sin(4.0 * l); + r -= pow(1.25 * e, 2.0) * sin(2.0 * m); + return 4.0 * degrees(r); } /** * Calculates the Sun's elevation as apparent * from a geographical position * - * @param tm The time in Julian Centuries + * @param t The time in Julian Centuries * @param latitude The latitude in degrees northwards from * the equator, negative for southwards * @param longitude The longitude in degrees eastwards from @@ -250,14 +250,14 @@ equation_of_time(double tm) * @return The Sun's apparent elevation at the specified time as seen * from the specified position, measured in radians */ -static inline double -solar_elevation_from_time(double tm, double latitude, double longitude) +static double +solar_elevation_from_time(double t, double latitude, double longitude) { - double rc = julian_centuries_to_julian_day(tm); - rc = (rc - round(rc) - 0.5) * 1440; - rc = 720.0 - rc - equation_of_time(tm); - rc = radians(rc / 4.0 - longitude); - return elevation_from_hour_angle(latitude, solar_declination(tm), rc); + double a = julian_centuries_to_julian_day(t); + a = (a - round(a) - 0.5) * 1440; + a = 720.0 - a - equation_of_time(t); + a = radians(a / 4.0 - longitude); + return elevation_from_hour_angle(latitude, solar_declination(t), a); } /** @@ -277,10 +277,10 @@ solar_elevation_from_time(double tm, double latitude, double longitude) double libred_solar_elevation(double latitude, double longitude, double *elevation) { - double tm; - if (julian_centuries(&tm)) + double t; + if (julian_centuries(&t)) return -1; - *elevation = degrees(solar_elevation_from_time(tm, latitude, longitude)); + *elevation = degrees(solar_elevation_from_time(t, latitude, longitude)); return 0; } |