Some more tests

Author: attipaci

CHANGELOG.md

@@ -14,7 +14,7 @@ available on the `main` branch.
 
 ### Fixed
 
- - `tt2tdb()` Had a wrong scaling in sinusoidal period., resulting in an error of up to +/- 1.7 ms.
+ - `tt2tdb()` Had a wrong scaling in sinusoidal period, resulting in an error of up to +/- 1.7 ms.
 
  - `tdb2tt()` had the wrong time offset in NOVAS C 3.1. Its zero was defined at J2000, whereas it should have been
    1977 January 1, 0h 0m 0s TAI, corrssponding to JD<sub>TT</sub> = 2443144.5003725.

include/novas.h

@@ -1105,7 +1105,7 @@ double novas_diff_time(const novas_timespec *t1, const novas_timespec *t2);
 
 double novas_diff_coordinate_time(const novas_timespec *t1, const novas_timespec *t2);
 
-int novas_increment_time(const novas_timespec *time, double seconds, novas_timespec *out);
+int novas_offset_time(const novas_timespec *time, double seconds, novas_timespec *out);
 
 
 // in frames.c

src/novas.c

@@ -5349,6 +5349,10 @@ double get_ut1_to_tt(int leap_seconds, double dut1) {
  * <ol>
  * <li>Fairhead, L. & Bretagnon, P. (1990) Astron. & Astrophys. 229, 240.</li>
  * <li>Kaplan, G. (2005), US Naval Observatory Circular 179.</li>
+ * <li><a href="https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html#The%20Relationship%20between%20TT%20and%20TDB">
+ * https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html</a></li>
+ * <li><a href="https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems">
+ * https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems</a></li>
  * </ol>
  *
  * @param jd_tdb         [day] Barycentric Dynamic Time (TDB) based Julian date
@@ -5368,6 +5372,11 @@ int tdb2tt(double jd_tdb, double *jd_tt, double *secdiff) {
           + 0.000005 * sin(606.9777 * t + 4.0212) + 0.000005 * sin(52.9691 * t + 0.4444) + 0.000002 * sin(21.3299 * t + 5.5431)
           + 0.000010 * t * sin(628.3076 * t + 4.2490);
 
+  // The simpler formula with a precision of ~30 us.
+//  const double t = (jd_tt - JD_J2000) / JULIAN_CENTURY_DAYS;
+//  const double g = 6.239996 + 630.0221385924 * t;
+//  const double d = 0.001657 * sin(g + 0.01671 * sin(g));
+
   if(jd_tt)
     *jd_tt = jd_tdb - d / DAY;
   if(secdiff)
@@ -5379,17 +5388,18 @@ int tdb2tt(double jd_tdb, double *jd_tt, double *secdiff) {
 /**
  * Returns the TDB - TT time difference in seconds for a given TT date.
  *
- *
- * Note, as of version 1.1, it uses the same calculation as the more precise original tdb2tt().
+ * Note, as of version 1.1, it uses the same calculation as the more precise original tdb2tt(). It thus has an acuracy of
+ * about 10 &mu;s vs around 30 &mu;s with the simpler formula from the references below.
  *
  *
  * REFERENCES
  * <ol>
+ * <li>Fairhead, L. & Bretagnon, P. (1990) Astron. & Astrophys. 229, 240.</li>
+ * <li>Kaplan, G. (2005), US Naval Observatory Circular 179.</li>
  * <li><a href="https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html#The%20Relationship%20between%20TT%20and%20TDB">
- * https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html</a>
+ * https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/time.html</a></li>
  * <li><a href="https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems">
- * https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems</a>
- * </li>
+ * https://gssc.esa.int/navipedia/index.php/Transformations_between_Time_Systems</a></li>
  * </ol>
  *
  * @param jd_tt     [day] Terrestrial Time (TT) based Julian date
@@ -5405,12 +5415,6 @@ double tt2tdb(double jd_tt) {
 
   tdb2tt(jd_tt, NULL, &dt);
   return dt;
-
-  /*
-  const double t = (jd_tt - JD_J2000) / JULIAN_CENTURY_DAYS;
-  const double g = 6.239996 + 630.0221385924 * t;
-  return 0.001657 * sin(g + 0.01671 * sin(g));
-  */
 }
 
 /**

src/timescale.c

@@ -27,6 +27,8 @@
 
 #define IDAY        86400                 ///< [s] 1 day
 
+#define IJD_J2000   2451545
+
 #define UNIX_SECONDS_0UTC_1JAN2000  946684800    ///< [s] UNIX time at J2000.0
 #define UNIX_J2000                  (UNIX_SECONDS_0UTC_1JAN2000 + (IDAY / 2))
 
@@ -156,19 +158,19 @@ int novas_set_split_time(enum novas_timescale timescale, long ijd, double fjd, i
  * @since 1.1
  * @author Attila Kovacs
  */
-int novas_increment_time(const novas_timespec *time, double seconds, novas_timespec *out) {
+int novas_offset_time(const novas_timespec *time, double seconds, novas_timespec *out) {
   int dd;
 
   if(!time || !out)
-    return novas_error(-1, EINVAL, "novas_increment_time", "NULL parameter: time=%p, out=%p", time, out);
+    return novas_error(-1, EINVAL, "novas_offset_time", "NULL parameter: time=%p, out=%p", time, out);
 
   if(out != time)
     *out = *time;
 
   out->fjd_tt += seconds / DAY;
   dd = (int) floor(out->fjd_tt);
   if(dd) {
-    out->fjd_tt -= dd * DAY;
+    out->fjd_tt -= dd;
     out->ijd_tt += dd;
   }
 
@@ -220,8 +222,6 @@ double novas_get_split_time(const novas_timespec *time, enum novas_timescale tim
     novas_error(-1, EINVAL, fn, "NULL input time specification");
     return NAN;
   }
-  if(timescale < 0 || timescale > NOVAS_TIMESCALES)
-    novas_error(-1, EINVAL, fn, "invalid timescale: %d", timescale);
 
   if(ijd)
     *ijd = time->ijd_tt;
@@ -281,7 +281,7 @@ double novas_get_split_time(const novas_timespec *time, enum novas_timescale tim
  *              will be set to EINVAL)
  *
  * @sa novas_set_time()
- * @sa novas_increment_time()
+ * @sa novas_offset_time()
  * @sa novas_diff_coordinate_time()
  *
  * @since 1.1
@@ -341,12 +341,14 @@ int novas_set_unix_time(time_t unix_time, long nanos, int leap, double dut1, nov
 
   // UTC based integer JD
   unix_time -= UNIX_J2000;
-  jd = NOVAS_JD_J2000 + unix_time / IDAY;
+  jd = IJD_J2000 + unix_time / IDAY;
 
   // seconds of JD date
   sojd = unix_time % IDAY;
-  if(sojd < 0)
+  if(sojd < 0) {
     sojd += IDAY;
+    jd--;
+  }
 
   return novas_set_split_time(NOVAS_UTC, jd, (sojd + 1e-9 * nanos) / DAY, leap, dut1, time);
 }
@@ -371,7 +373,7 @@ time_t novas_get_unix_time(const novas_timespec *time, long *nanos) {
 
   sod = novas_get_split_time(time, NOVAS_UTC, &ijd) * DAY;
   isod = floor(sod);
-  seconds = UNIX_J2000 + (ijd - NOVAS_JD_J2000) * DAY + isod;
+  seconds = UNIX_J2000 + (ijd - IJD_J2000) * IDAY + isod;
 
   if(nanos) {
     *nanos = round(1e9 * (sod - isod));

test/src/test-errors.c

@@ -874,6 +874,28 @@ static int test_obs_posvel() {
   return n;
 }
 
+static int test_time() {
+  novas_timespec time = {};
+  int n = 0;
+
+  if(check("time:set:time", -1, novas_set_time(NOVAS_TT, NOVAS_JD_J2000, 37, 0.11, NULL))) n++;
+  if(check("time:set:scale:-1", -1, novas_set_time(-1, NOVAS_JD_J2000, 37, 0.11, &time))) n++;
+  if(check("time:set:scale:hi", -1, novas_set_time(NOVAS_TIMESCALES, NOVAS_JD_J2000, 37, 0.11, &time))) n++;
+
+  if(check("time:get:time", -1, novas_get_time(NULL, NOVAS_TT))) n++;
+  if(check("time:get:scale:-1", -1, novas_get_time(&time, -1))) n++;
+  if(check("time:get:scale:hi", -1, novas_get_time(&time, NOVAS_TIMESCALES))) n++;
+
+  if(check("time:offset:time", -1, novas_offset_time(NULL, 0.1, &time))) n++;
+  if(check("time:offset:out", -1, novas_offset_time(&time, 0.1, NULL))) n++;
+  if(check("time:offset:both", -1, novas_offset_time(NULL, 0.1, NULL))) n++;
+
+  if(check("time:diff:t1", -1, novas_diff_time(NULL, &time))) n++;
+  if(check("time:diff:t2", -1, novas_diff_time(&time, NULL))) n++;
+  if(check("time:diff:both", -1, novas_diff_time(NULL, NULL))) n++;
+
+  return n;
+}
 
 int main() {
   int n = 0;