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iers.c File Reference

## Macros

#define | IERS_DATACENTER "datacenter.iers.org"
| IERS EOP server name.
#define | IERS_LEAP_SERVER "hpiers.obspm.fr"
| IERS leap-seconds.list server name.
#define | NOVAS_EOP_ALT_C01_URL "https://hpiers.obspm.fr/iers/eop/eopc01/eopc01.1846-now"
| Alternative URL for the IERS C01 series Earth Orientation Parameter data series from 1846 to the current date, at 0.1 year interval to 1899, and 0.05 year interval after.
#define | NOVAS_EOP_ALT_C04_URL "https://hpiers.obspm.fr/iers/eop/eopc04/eopc04.1962-now"
| Alternative URL for the IERS C04 daily series Earth Orientation Parameter data series from 1962 to the current date.
#define | NOVAS_EOP_ALT_LEAP_URL "https://data.iana.org/time-zones/data/leap-seconds.list"
| Alternative URL for leap-seconds.list.
#define | NOVAS_EOP_ALT_RAPID_URL "https://maia.usno.navy.mil/ser7/finals2000A.daily.extended"
| Alternative URL for the IERS rapid dailyseries Earth Orientation Parameter data series from 1973, and including predictions for up to to a year from the current date.

## Functions

int | novas_fetch_eop (double jd, long timeout_millis, novas_eop *eop)
| Obtains interpolated Earth Orientation Parameter data from the International Earth Rotation and Reference Systems Service (IERS).
int | novas_fetch_eop_unix (time_t t, long timeout_millis, novas_eop *eop)
| Obtains interpolated Earth Orientation Parameter data from the International Earth Rotation and Reference Systems Service (IERS) around the current system time, using the rapid service data (finals.all).
int | novas_get_eop_itrf_year (enum novas_eop_series series)
| Returns the ITRF realization year for a given IERS Earth Orientation Parameter (EOP) series.
const char * | novas_get_eop_url (enum novas_eop_series series)
| Returns the URL currently configured for a given IERS Earth Orientation Parameter (EOP) series.
int | novas_is_auto_fetch_eop ()
| Checks if automatic fetching of Earth Orientation Parameter values from IERS is allowed.
int | novas_lookup_leap (time_t t)
| Returns the leap seconds for the given UNIX timestamp, based either on a locally supplied leap seconds list (see novas_set_leap_list()), or else from data obtained as needed from IERS (provided that fetching it is allowed).
void | novas_reset_eop ()
| Releases resources used by URL handles used for obtaining Earth Orientation Parameter (EOP) data from the International Earth Rotation and Reference Systems Service (IERS), including the leap seconds list supplied earlier or obtained from IERS.
int | novas_set_auto_fetch_eop (int enabled)
| Disable or Re-enabled the automatic fetching of Earth Orientation Parameter values from IERS, when these are left undefined (NAN) when initializing astrometric time or observing frame instances.
int | novas_set_eop_url (enum novas_eop_series series, int itrf_year, const char *url)
| Specify a URL to use for a given IERS Earth Orientation Parameter (EOP) series.
int | novas_set_leap_list (const char *filename)
| Specifies a local file containing the official leap seconds list, i.e.

## Detailed Description

Date
  Created on Apr 18, 2026

Author
  Attila Kovacs and Kiran Shila

Functions to obtain and manage Earth Orientation data from the International Earth Rotation and Reference Systems Service (IERS) via HTTPS, or using other (remote or local) URLs.

The functions in this module are generally thread-safe. That is, you may call all functions from concurrent threads without data corruption. However, note that the EOP resources (URLs and/or local files), and the setting that enables/disables automatic fetching, are global settings. Thus, changing these in one thread will affect subsequent EOP fetch calls in other threads also.

See also
  Earth orientation

## Macro Definition Documentation

## IERS_DATACENTER

#define IERS_DATACENTER "datacenter.iers.org"

IERS EOP server name.

## IERS_LEAP_SERVER

#define IERS_LEAP_SERVER "hpiers.obspm.fr"

IERS leap-seconds.list server name.

## NOVAS_EOP_ALT_C01_URL

#define NOVAS_EOP_ALT_C01_URL "https://hpiers.obspm.fr/iers/eop/eopc01/eopc01.1846-now"

Alternative URL for the IERS C01 series Earth Orientation Parameter data series from 1846 to the current date, at 0.1 year interval to 1899, and 0.05 year interval after.

See also
  novas_set_eop_url(), EOP_C01_IAU2000

## NOVAS_EOP_ALT_C04_URL

#define NOVAS_EOP_ALT_C04_URL "https://hpiers.obspm.fr/iers/eop/eopc04/eopc04.1962-now"

Alternative URL for the IERS C04 daily series Earth Orientation Parameter data series from 1962 to the current date.

See also
  novas_set_eop_url(), EOP_C04_IAU2000_0UTC

## NOVAS_EOP_ALT_LEAP_URL

#define NOVAS_EOP_ALT_LEAP_URL "https://data.iana.org/time-zones/data/leap-seconds.list"

Alternative URL for leap-seconds.list.

See also
  novas_set_eop_url(), EOP_LEAP_LIST

## NOVAS_EOP_ALT_RAPID_URL

#define NOVAS_EOP_ALT_RAPID_URL "https://maia.usno.navy.mil/ser7/finals2000A.daily.extended"

Alternative URL for the IERS rapid dailyseries Earth Orientation Parameter data series from 1973, and including predictions for up to to a year from the current date.

See also
  novas_set_eop_url(), EOP_RAPID_IAU2000