Definition
Each satellite transmits its own detailed orbital parameters and clock corrections within the navigation message, allowing the receiver to compute the satellite's position at the instant of transmission. Ephemeris data is only valid for a few hours and must be refreshed; downloading a fresh set takes roughly thirty seconds of continuous tracking per satellite. Stale or missing ephemeris is the usual reason a receiver switched on after a long lay-up is slow to fix.
Want to apply this on the water?
Ask Saily out loud for an example, a scenario or a simpler explanation.
Talk to Saily