GPS Vs. GLONASS Vs. Galileo: What’s The Best GNSS?

[Jan Horn]

With the Galileo GNSS now fully operational it may be beneficial to read the article at

https://expertworldtravel.com/gps-vs-gl ... %20project.

I noticed recently that my Garmin Drive Assist also lock onto some of the galileo satellites and that caused me to start scratching around on the net.

I believe that originally there were a slight time difference between GPS and Galileo which have been resolved

With satellite navigation based around the highly accurate measurement of signal travel times, both Galileo and GPS have their own internal reference time systems used to synchronise all system clocks and signals.

The problem is these time systems are not quite identical, with Galileo System Time being around 50 nanoseconds or less apart from GPS time.

“A nanosecond is only a billionth of a second, corresponding to the time light takes to travel 30 cm,” explains Jörg Hahn, Galileo System Engineering Manager.

“But this soon adds up, and for anyone attempting to use the two systems together might find this ‘offset’ accounting for up to 15 m of error, causing an unacceptable contribution to user performance.”

Instead, this time offset needs to be known or estimated by the receiver itself.

You can read all about this at

https://www.esa.int/Applications/Naviga ... g_together