The concept of time in navigation

The article discusses the concept of time in navigation, especially in marine navigation, as well as selected time measures, among others: Greenwich Mean Time (GMT), Universal Time Coordinated (UTC), International Atomic Time TAI (Temps Atomique International), GPST (Global Positioning System Time) eLoran Time and interrelation between these measures. Understanding how time is involved in navigation, and using it, is one of the navigator's most important duties. Nowadays we have satellite navigation to help us know where we are. These satellites contain several very precise and accurate clocks, because time and location are completely and totally inter-related in satellite navigation. There is growing interest internationally concerning the vulnerability Global Navigation Satellite Systems (GNSS) to natural and man-made interference, plus the jamming and spoofing of their transmissions. These vulnerabilities have led to a demand for sources of resilient PNT (Positioning, Navigation and Timing) [16], including a robust means of distributing precise time nationally and internationally.