| File: | weather-sun.c |
| Warning: | line 165, column 13 Value stored to 'obsLon' during its initialization is never read |
Press '?' to see keyboard shortcuts
Keyboard shortcuts:
| 1 | /* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 4 -*- */ |
| 2 | /* weather-sun.c - Astronomy calculations for cafeweather |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or |
| 5 | * modify it under the terms of the GNU General Public License as |
| 6 | * published by the Free Software Foundation; either version 2 of the |
| 7 | * License, or (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, but |
| 10 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 12 | * General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, see |
| 16 | * <http://www.gnu.org/licenses/>. |
| 17 | */ |
| 18 | |
| 19 | /* |
| 20 | * Formulas from: |
| 21 | * "Practical Astronomy With Your Calculator" (3e), Peter Duffett-Smith |
| 22 | * Cambridge University Press 1988 |
| 23 | * Unless otherwise noted, comments referencing "steps" are related to |
| 24 | * the algorithm presented in section 49 of above |
| 25 | */ |
| 26 | |
| 27 | #ifdef HAVE_CONFIG_H1 |
| 28 | #include <config.h> |
| 29 | #endif |
| 30 | |
| 31 | #include <math.h> |
| 32 | #include <time.h> |
| 33 | #include <glib.h> |
| 34 | |
| 35 | #define CAFEWEATHER_I_KNOW_THIS_IS_UNSTABLE |
| 36 | #include "weather-priv.h" |
| 37 | |
| 38 | #define ECCENTRICITY(d)(0.01671123 - (d)/36525.*0.00004392) (0.01671123 - (d)/36525.*0.00004392) |
| 39 | |
| 40 | /* |
| 41 | * Ecliptic longitude of the sun at specified time (UT) |
| 42 | * The algoithm is described in section 47 of Duffett-Smith |
| 43 | * Return value is in radians |
| 44 | */ |
| 45 | gdouble |
| 46 | sunEclipLongitude(time_t t) |
| 47 | { |
| 48 | gdouble ndays, meanAnom, eccenAnom, delta, e, longitude; |
| 49 | |
| 50 | /* |
| 51 | * Start with an esticafe based on a fixed daily rate |
| 52 | */ |
| 53 | ndays = EPOCH_TO_J2000(t)((gdouble)(t)-946727935.816) / 86400.; |
| 54 | meanAnom = DEGREES_TO_RADIANS(MEAN_ECLIPTIC_LONGITUDE(ndays)((fmod (((280.46457166 + (ndays)/36525.*35999.37244981) - (282.93768193 + (ndays)/36525.*0.32327364)),360.) / 180.) * 3.14159265358979323846 ) |
| 55 | - PERIGEE_LONGITUDE(ndays))((fmod (((280.46457166 + (ndays)/36525.*35999.37244981) - (282.93768193 + (ndays)/36525.*0.32327364)),360.) / 180.) * 3.14159265358979323846 ); |
| 56 | |
| 57 | /* |
| 58 | * Approximate solution of Kepler's equation: |
| 59 | * Find E which satisfies E - e sin(E) = M (mean anomaly) |
| 60 | */ |
| 61 | eccenAnom = meanAnom; |
| 62 | e = ECCENTRICITY(ndays)(0.01671123 - (ndays)/36525.*0.00004392); |
| 63 | |
| 64 | while (1e-12 < fabs( delta = eccenAnom - e * sin(eccenAnom) - meanAnom)) |
| 65 | { |
| 66 | eccenAnom -= delta / (1.- e * cos(eccenAnom)); |
| 67 | } |
| 68 | |
| 69 | /* |
| 70 | * Earth's longitude on the ecliptic |
| 71 | */ |
| 72 | longitude = fmod( DEGREES_TO_RADIANS (PERIGEE_LONGITUDE(ndays))((fmod (((282.93768193 + (ndays)/36525.*0.32327364)),360.) / 180. ) * 3.14159265358979323846) |
| 73 | + 2. * atan (sqrt ((1.+e)/(1.-e)) |
| 74 | * tan (eccenAnom / 2.)), |
| 75 | 2. * M_PI3.14159265358979323846); |
| 76 | if (longitude < 0.) { |
| 77 | longitude += 2 * M_PI3.14159265358979323846; |
| 78 | } |
| 79 | return longitude; |
| 80 | } |
| 81 | |
| 82 | static gdouble |
| 83 | ecliptic_obliquity (gdouble time) |
| 84 | { |
| 85 | gdouble jc = EPOCH_TO_J2000 (time)((gdouble)(time)-946727935.816) / (36525. * 86400.); |
| 86 | gdouble eclip_secs = (84381.448 |
| 87 | - (46.84024 * jc) |
| 88 | - (59.e-5 * jc * jc) |
| 89 | + (1.813e-3 * jc * jc * jc)); |
| 90 | return DEGREES_TO_RADIANS(eclip_secs / 3600.)((fmod ((eclip_secs / 3600.),360.) / 180.) * 3.14159265358979323846 ); |
| 91 | } |
| 92 | |
| 93 | /* |
| 94 | * Convert ecliptic longitude and latitude (radians) to equitorial |
| 95 | * coordinates, expressed as right ascension (hours) and |
| 96 | * declination (radians) |
| 97 | */ |
| 98 | void |
| 99 | ecl2equ (gdouble time, |
| 100 | gdouble eclipLon, gdouble eclipLat, |
| 101 | gdouble *ra, gdouble *decl) |
| 102 | { |
| 103 | gdouble mEclipObliq = ecliptic_obliquity(time); |
| 104 | |
| 105 | if (ra) { |
| 106 | *ra = RADIANS_TO_HOURS (atan2 ((sin (eclipLon) * cos (mEclipObliq)((atan2 ((sin (eclipLon) * cos (mEclipObliq) - tan (eclipLat) * sin(mEclipObliq)), cos (eclipLon))) * 12. / 3.14159265358979323846 ) |
| 107 | - tan (eclipLat) * sin(mEclipObliq)),((atan2 ((sin (eclipLon) * cos (mEclipObliq) - tan (eclipLat) * sin(mEclipObliq)), cos (eclipLon))) * 12. / 3.14159265358979323846 ) |
| 108 | cos (eclipLon)))((atan2 ((sin (eclipLon) * cos (mEclipObliq) - tan (eclipLat) * sin(mEclipObliq)), cos (eclipLon))) * 12. / 3.14159265358979323846 ); |
| 109 | if (*ra < 0.) |
| 110 | *ra += 24.; |
| 111 | } |
| 112 | if (decl) { |
| 113 | *decl = asin (( sin (eclipLat) * cos (mEclipObliq)) |
| 114 | + cos (eclipLat) * sin (mEclipObliq) * sin(eclipLon)); |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | /* |
| 119 | * Calculate rising and setting times for an object |
| 120 | * based on it equitorial coordinates (section 33 & 15) |
| 121 | * Returned "rise" and "set" values are sideral times in hours |
| 122 | */ |
| 123 | static void |
| 124 | gstObsv (gdouble ra, gdouble decl, |
| 125 | gdouble obsLat, gdouble obsLon, |
| 126 | gdouble *rise, gdouble *set) |
| 127 | { |
| 128 | double a = acos (-tan (obsLat) * tan (decl)); |
| 129 | double b; |
| 130 | |
| 131 | if (isnan (a)__builtin_isnan (a) != 0) { |
| 132 | *set = *rise = a; |
| 133 | return; |
| 134 | } |
| 135 | a = RADIANS_TO_HOURS (a)((a) * 12. / 3.14159265358979323846); |
| 136 | b = 24. - a + ra; |
| 137 | a += ra; |
| 138 | a -= RADIANS_TO_HOURS (obsLon)((obsLon) * 12. / 3.14159265358979323846); |
| 139 | b -= RADIANS_TO_HOURS (obsLon)((obsLon) * 12. / 3.14159265358979323846); |
| 140 | if ((a = fmod (a, 24.)) < 0) |
| 141 | a += 24.; |
| 142 | if ((b = fmod (b, 24.)) < 0) |
| 143 | b += 24.; |
| 144 | |
| 145 | *set = a; |
| 146 | *rise = b; |
| 147 | } |
| 148 | |
| 149 | |
| 150 | static gdouble |
| 151 | t0 (time_t date) |
| 152 | { |
| 153 | gdouble t = ((gdouble)(EPOCH_TO_J2000 (date)((gdouble)(date)-946727935.816) / 86400)) / 36525.0; |
| 154 | gdouble t0 = fmod (6.697374558 + 2400.051366 * t + 2.5862e-5 * t * t, 24.); |
| 155 | if (t0 < 0.) |
| 156 | t0 += 24.; |
| 157 | return t0; |
| 158 | } |
| 159 | |
| 160 | |
| 161 | static gboolean |
| 162 | calc_sun2 (WeatherInfo *info, time_t t) |
| 163 | { |
| 164 | gdouble obsLat = info->location->latitude; |
| 165 | gdouble obsLon = info->location->longitude; |
Value stored to 'obsLon' during its initialization is never read | |
| 166 | time_t gm_midn; |
| 167 | time_t lcl_midn; |
| 168 | gdouble gm_hoff, lambda; |
| 169 | gdouble ra1, ra2; |
| 170 | gdouble decl1, decl2; |
| 171 | gdouble decl_midn, decl_noon; |
| 172 | gdouble rise1, rise2; |
| 173 | gdouble set1, set2; |
| 174 | gdouble tt, t00; |
| 175 | gdouble x, u, dt; |
| 176 | |
| 177 | /* Approximate preceding local midnight at observer's longitude */ |
| 178 | obsLat = info->location->latitude; |
| 179 | obsLon = info->location->longitude; |
| 180 | gm_midn = t - (t % 86400); |
| 181 | gm_hoff = floor ((RADIANS_TO_DEGREES (obsLon)((obsLon) * 180. / 3.14159265358979323846) + 7.5) / 15.); |
| 182 | lcl_midn = gm_midn - 3600. * gm_hoff; |
| 183 | if (t - lcl_midn >= 86400) |
| 184 | lcl_midn += 86400; |
| 185 | else if (lcl_midn > t) |
| 186 | lcl_midn -= 86400; |
| 187 | |
| 188 | lambda = sunEclipLongitude (lcl_midn); |
| 189 | |
| 190 | /* |
| 191 | * Calculate equitorial coordinates of sun at previous |
| 192 | * and next local midnights |
| 193 | */ |
| 194 | ecl2equ (lcl_midn, lambda, 0., &ra1, &decl1); |
| 195 | ecl2equ (lcl_midn + 86400., |
| 196 | lambda + DEGREES_TO_RADIANS(SOL_PROGRESSION)((fmod (((360./365.242191)),360.) / 180.) * 3.14159265358979323846 ), 0., |
| 197 | &ra2, &decl2); |
| 198 | |
| 199 | /* |
| 200 | * If the observer is within the Arctic or Antarctic Circles then |
| 201 | * the sun may be above or below the horizon for the full day. |
| 202 | */ |
| 203 | decl_midn = MIN(decl1,decl2)(((decl1) < (decl2)) ? (decl1) : (decl2)); |
| 204 | decl_noon = (decl1+decl2)/2.; |
| 205 | info->midnightSun = |
| 206 | (obsLat > (M_PI3.14159265358979323846/2.-decl_midn)) || (obsLat < (-M_PI3.14159265358979323846/2.-decl_midn)); |
| 207 | info->polarNight = |
| 208 | (obsLat > (M_PI3.14159265358979323846/2.+decl_noon)) || (obsLat < (-M_PI3.14159265358979323846/2.+decl_noon)); |
| 209 | if (info->midnightSun || info->polarNight) { |
| 210 | info->sunriseValid = info->sunsetValid = FALSE(0); |
| 211 | return FALSE(0); |
| 212 | } |
| 213 | |
| 214 | /* |
| 215 | * Convert to rise and set times based positions for the preceding |
| 216 | * and following local midnights. |
| 217 | */ |
| 218 | gstObsv (ra1, decl1, obsLat, obsLon - (gm_hoff * M_PI3.14159265358979323846 / 12.), &rise1, &set1); |
| 219 | gstObsv (ra2, decl2, obsLat, obsLon - (gm_hoff * M_PI3.14159265358979323846 / 12.), &rise2, &set2); |
| 220 | |
| 221 | /* TODO: include calculations for regions near the poles. */ |
| 222 | if (isnan(rise1)__builtin_isnan (rise1) || isnan(rise2)__builtin_isnan (rise2)) { |
| 223 | info->sunriseValid = info->sunsetValid = FALSE(0); |
| 224 | return FALSE(0); |
| 225 | } |
| 226 | |
| 227 | if (rise2 < rise1) { |
| 228 | rise2 += 24.; |
| 229 | } |
| 230 | if (set2 < set1) { |
| 231 | set2 += 24.; |
| 232 | } |
| 233 | |
| 234 | tt = t0(lcl_midn); |
| 235 | t00 = tt - (gm_hoff + RADIANS_TO_HOURS(obsLon)((obsLon) * 12. / 3.14159265358979323846)) * 1.002737909; |
| 236 | |
| 237 | if (t00 < 0.) |
| 238 | t00 += 24.; |
| 239 | |
| 240 | if (rise1 < t00) { |
| 241 | rise1 += 24.; |
| 242 | rise2 += 24.; |
| 243 | } |
| 244 | if (set1 < t00) { |
| 245 | set1 += 24.; |
| 246 | set2 += 24.; |
| 247 | } |
| 248 | |
| 249 | /* |
| 250 | * Interpolate between the two to get a rise and set time |
| 251 | * based on the sun's position at local noon (step 8) |
| 252 | */ |
| 253 | rise1 = (24.07 * rise1 - t00 * (rise2 - rise1)) / (24.07 + rise1 - rise2); |
| 254 | set1 = (24.07 * set1 - t00 * (set2 - set1)) / (24.07 + set1 - set2); |
| 255 | |
| 256 | /* |
| 257 | * Calculate an adjustment value to account for parallax, |
| 258 | * refraction and the Sun's finite diameter (steps 9,10) |
| 259 | */ |
| 260 | decl2 = (decl1 + decl2) / 2.; |
| 261 | x = DEGREES_TO_RADIANS(0.830725)((fmod ((0.830725),360.) / 180.) * 3.14159265358979323846); |
| 262 | u = acos ( sin(obsLat) / cos(decl2) ); |
| 263 | dt = RADIANS_TO_HOURS ( asin ( sin(x) / sin(u) ) / cos(decl2) )((asin ( sin(x) / sin(u) ) / cos(decl2)) * 12. / 3.14159265358979323846 ); |
| 264 | |
| 265 | /* |
| 266 | * Subtract the correction value from sunrise and add to sunset, |
| 267 | * then (step 11) convert sideral times to UT |
| 268 | */ |
| 269 | rise1 = (rise1 - dt - tt) * 0.9972695661; |
| 270 | if (rise1 < 0.) |
| 271 | rise1 += 24; |
| 272 | else if (rise1 >= 24.) |
| 273 | rise1 -= 24.; |
| 274 | info->sunriseValid = ((rise1 >= 0.) && (rise1 < 24.)); |
| 275 | info->sunrise = (rise1 * 3600.) + lcl_midn; |
| 276 | |
| 277 | set1 = (set1 + dt - tt) * 0.9972695661; |
| 278 | if (set1 < 0.) |
| 279 | set1 += 24; |
| 280 | else if (set1 >= 24.) |
| 281 | set1 -= 24.; |
| 282 | info->sunsetValid = ((set1 >= 0.) && (set1 < 24.)); |
| 283 | info->sunset = (set1 * 3600.) + lcl_midn; |
| 284 | |
| 285 | return (info->sunriseValid || info->sunsetValid); |
| 286 | } |
| 287 | |
| 288 | |
| 289 | /** |
| 290 | * calc_sun_time: |
| 291 | * @info: #WeatherInfo structure containing the observer's latitude |
| 292 | * and longitude in radians, fills in the sunrise and sunset times. |
| 293 | * @t: time_t |
| 294 | * |
| 295 | * Returns: gboolean indicating if the results are valid. |
| 296 | */ |
| 297 | gboolean |
| 298 | calc_sun_time (WeatherInfo *info, time_t t) |
| 299 | { |
| 300 | return info->location->latlon_valid && calc_sun2 (info, t); |
| 301 | } |
| 302 | |
| 303 | /** |
| 304 | * calc_sun: |
| 305 | * @info: #WeatherInfo structure containing the observer's latitude |
| 306 | * and longitude in radians, fills in the sunrise and sunset times. |
| 307 | * |
| 308 | * Returns: gboolean indicating if the results are valid. |
| 309 | */ |
| 310 | gboolean |
| 311 | calc_sun (WeatherInfo *info) |
| 312 | { |
| 313 | return calc_sun_time(info, time(NULL((void*)0))); |
| 314 | } |
| 315 | |
| 316 | |
| 317 | /** |
| 318 | * weather_info_next_sun_event: |
| 319 | * @info: #WeatherInfo structure |
| 320 | * |
| 321 | * Returns: the interval, in seconds, until the next "sun event": |
| 322 | * - local midnight, when rise and set times are recomputed |
| 323 | * - next sunrise, when icon changes to daytime version |
| 324 | * - next sunset, when icon changes to nighttime version |
| 325 | */ |
| 326 | gint |
| 327 | weather_info_next_sun_event (WeatherInfo *info) |
| 328 | { |
| 329 | time_t now = time (NULL((void*)0)); |
| 330 | struct tm ltm; |
| 331 | time_t nxtEvent; |
| 332 | |
| 333 | g_return_val_if_fail (info != NULL, -1)do { if ((info != ((void*)0))) { } else { g_return_if_fail_warning ("CafeWeather", ((const char*) (__func__)), "info != NULL"); return (-1); } } while (0); |
| 334 | |
| 335 | if (!calc_sun (info)) |
| 336 | return -1; |
| 337 | |
| 338 | /* Determine when the next local midnight occurs */ |
| 339 | (void) localtime_r (&now, <m); |
| 340 | ltm.tm_sec = 0; |
| 341 | ltm.tm_min = 0; |
| 342 | ltm.tm_hour = 0; |
| 343 | ltm.tm_mday++; |
| 344 | nxtEvent = mktime (<m); |
| 345 | |
| 346 | if (info->sunsetValid && |
| 347 | (info->sunset > now) && (info->sunset < nxtEvent)) |
| 348 | nxtEvent = info->sunset; |
| 349 | if (info->sunriseValid && |
| 350 | (info->sunrise > now) && (info->sunrise < nxtEvent)) |
| 351 | nxtEvent = info->sunrise; |
| 352 | return (gint)(nxtEvent - now); |
| 353 | } |