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Use struct timespec instead of time_t for increased time precision.

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This commit is contained in:
Jon Lund Steffensen
2009-12-28 14:59:41 +01:00
parent 1846f040ea
commit 8595c4887e
2 changed files with 20 additions and 14 deletions
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src/solar.c
+17 -12
View File
@@ -47,17 +47,22 @@ static const double time_angle[] = {
/* Unix time from Julian day */
static time_t
unix_time_from_jd(double jd)
static struct timespec
timespec_from_jd(double jd)
{
return 86400.0*(jd - 2440587.5);
struct timespec t;
double secs = 86400.0*(jd - 2440587.5);
t.tv_sec = floor(secs);
t.tv_nsec = (secs - t.tv_sec) * 1000000000.0;
return t;
}
/* Julian day from unix time */
static double
jd_from_unix_time(time_t t)
jd_from_timespec(struct timespec t)
{
return (t / 86400.0) + 2440587.5;
return (t.tv_sec / 86400.0) +
(t.tv_nsec / 86400000000000.0) + 2440587.5;
}
/* Julian centuries since J2000.0 from Julian day */
@@ -283,17 +288,17 @@ solar_elevation_from_time(double t, double lat, double lon)
}
double
solar_elevation(time_t date, double lat, double lon)
solar_elevation(struct timespec date, double lat, double lon)
{
double jd = jd_from_unix_time(date);
double jd = jd_from_timespec(date);
return DEG(solar_elevation_from_time(jcent_from_jd(jd), lat, lon));
}
void
solar_table_fill(time_t date, double lat, double lon, time_t *table)
solar_table_fill(struct timespec date, double lat, double lon, time_t *table)
{
/* Calculate Julian day */
double jd = jd_from_unix_time(date);
double jd = jd_from_timespec(date);
/* Calculate Julian day number */
double jdn = round(jd);
@@ -303,16 +308,16 @@ solar_table_fill(time_t date, double lat, double lon, time_t *table)
double sol_noon = time_of_solar_noon(t, lon);
double j_noon = jdn - 0.5 + sol_noon/1440.0;
double t_noon = jcent_from_jd(j_noon);
table[SOLAR_TIME_NOON] = unix_time_from_jd(j_noon);
table[SOLAR_TIME_NOON] = timespec_from_jd(j_noon).tv_sec;
/* Calculate solar midnight */
table[SOLAR_TIME_MIDNIGHT] = unix_time_from_jd(j_noon + 0.5);
table[SOLAR_TIME_MIDNIGHT] = timespec_from_jd(j_noon + 0.5).tv_sec;
/* Calulate absoute time of other phenomena */
for (int i = 2; i < SOLAR_TIME_MAX; i++) {
double angle = time_angle[i];
double offset =
time_of_solar_elevation(t, t_noon, lat, lon, angle);
table[i] = unix_time_from_jd(jdn - 0.5 + offset/1440.0);
table[i] = timespec_from_jd(jdn - 0.5 + offset/1440.0).tv_sec;
}
}
src/solar.h
+3 -2
View File
@@ -44,7 +44,8 @@ typedef enum {
SOLAR_TIME_MAX
} solar_time_t;
double solar_elevation(time_t t, double lat, double lon);
void solar_table_fill(time_t date, double lat, double lon, time_t *table);
double solar_elevation(struct timespec date, double lat, double lon);
void solar_table_fill(struct timespec date, double lat, double lon,
time_t *table);
#endif /* ! _SOLAR_H */