GNSStidskilder

GNSStidskilder, or GNSS time sources, are time references derived from Global Navigation Satellite System signals that are used to discipline local clocks and synchronize equipment and networks. They extract precise timing information from satellite atomic clocks and propagate it to receivers on the ground, enabling clocks to maintain accurate time with high stability and traceability. In practice, a GNSS time source disciplines a local oscillator (for example in a cesium or rubidium clock) to keep time accurate even between GNSS updates.

The main GNSS constellations include GPS, GLONASS, Galileo, and BeiDou. Each provides its own time scale: GPS Time, GLONASS Time, Galileo System Time, and BeiDou Time. These scales are continuous and precise but are not identical to Coordinated Universal Time (UTC). UTC includes leap seconds, while GNSS time scales do not; the result is a known offset between GNSS time and UTC that changes when leap seconds are added.

GNSS time sources are widely used in telecommunications networks, electrical power grids, financial trading platforms, and data centers, where synchronized timing is essential for event sequencing, logging, and regulatory compliance. In many deployments, GNSS time is distributed inside an organization via a GNSS-disciplined oscillator, using NTP or PTP to deliver time to end devices. Redundancy and holdover capability are common to ensure reliability during GNSS outages.

Security and reliability considerations include vulnerability to jamming and spoofing. Mitigations include multi-constellation reception, antenna protections, cryptographic authentication where available, and cross-checking with alternative time sources to maintain accurate time under adverse conditions.