Bonjour à tous et bienvenue sur ce Gitlab. Pour échanger avec ses autres utilisateurs, posez vos questions ou trouver des ressources, vous pouvez rejoindre le canal suivant : https://chat.univ-eiffel.fr/channel/forges-logicielles-github-et-gitlab-universite-gustave-eiffel

Skip to content

Changes

Page history
Update Time reference authored by Brian Histe's avatar Brian Histe
Show whitespace changes
Inline Side-by-side
Time-reference.md
View page @ efc139c5
......@@ -2,22 +2,24 @@ The time reference in a GNSS is the standard of time used by the system to synch
The time reference used in GNSS is **Coordinated Universal Time (UTC)**, which is the international standard of time that is based on the rotation of the Earth. The UTC time is maintained by the **International Atomic Time (TAI)** and is coordinated by the **International Bureau of Weights and Measures (BIPM)**.
[![mqdefault](uploads/d18b07be4814a563c10282c5e8a3905f/mqdefault.jpg)](https://www.youtube.com/watch?v=QLW01qDakVs)
The GNSS satellites are equipped with atomic clocks that are used to generate the navigation signals. These clocks are extremely accurate and are able to maintain their time to within a few nanoseconds of the UTC time reference.
The GNSS receivers also have an internal clock, which is used to measure the time of arrival of the navigation signals. This internal clock must be synchronized with the UTC time reference in order to calculate the position and velocity of the receiver accurately.
The time reference is also used in the determination of the satellite's ephemeris, which is a set of parameters that describes the satellite's position and velocity at a given time. The ephemeris is transmitted to the receivers along with the navigation signals and it is used to calculate the position and velocity of the receiver.
The main problem with the time frame is that it differs between constellations.
Here is the table that establishes the relationship between the constellations' time references.
The main problem with the time frame is that it differs between constellations. Here is the table that establishes the relationship between the constellations' time references.
![Capture_d_écran_2023-01-20_141743](uploads/9720d03017b05215d549111b773247a6/Capture_d_écran_2023-01-20_141743.png)
![Capture_d\_écran_2023-01-20_141743](uploads/9720d03017b05215d549111b773247a6/Capture_d\_%C3%A9cran_2023-01-20_141743.png)
With :
- GPST GPS Time,
- Galileo System Time (GST)
- Beidou Time (BDT)
Overall, the time reference in a GNSS is a crucial component of the system. It is used to ensure that the navigation signals are received by the GNSS receivers at the correct time and that the calculated position and velocity are accurate. The time reference used in GNSS is **Coordinated Universal Time (UTC)** and it is maintained by the **International Atomic Time (TAI)** and is coordinated by the **International Bureau of Weights and Measures (BIPM)**. The GNSS satellites and receivers are equipped with atomic clocks that are synchronized with the UTC time reference to ensure accurate positioning and velocity calculations.
#### Sources :
- [https://www.iers.org/IERS/EN/Home/home_node.html](https://www.iers.org/IERS/EN/Home/home_node.html)
- [https://gssc.esa.int/navipedia/index.php/Atomic_Time](https://gssc.esa.int/navipedia/index.php/Atomic_Time)
\ No newline at end of file