Global Navigation Satellite Systems (GNSS) like GPS, GLONASS, Galileo and Beidou provide positioning, navigation, and timing services that are crucial to critical infrastructure. Timing is the most essential of these services, relied on by sectors like communications, energy, finance, and transportation. The development of a worldwide, resilient, and precise timing reference will require a fully integrated global system of systems for position, navigation, and timing.

1. GNSS and Timing:
the Need for a Global
PNT Infrastructure
Dr. ing. Marco Lisi
(marco.lisi@ieee.org)
International Workshop on "GNSS technologies advances
in a multiconstellation framework“
SOGEI, Roma, 21-22 January 2016

2. What then is time?
“What then is time? If no
one ask me, I know.
If someone ask me to
explain, I know not.”
Saint Augustine of Ippo
Confessions, Book XI, Chapter
XIV

3. Summary
• Global Navigation Satellite Systems, such as GPS, GLONASS,
Galileo and Beidou, constitute a worldwide utility, tightly
interconnected with all other critical infrastructures, from
electric power distribution systems to air traffic
management systems, from railways to water and oil piping
networks;
• Timing is the most strategic and essential of the services
offered by GNSS’s, and the one most affecting all critical
infrastructures of our society;
• The sectors most relying on GNSS’s for timing are
communications (e.g. Internet, cellular networks and
satellite networks), energy, financial services and
transportation systems;
• The promise for a worldwide, reliable, continuous, resilient
and precise timing reference is likely to lie in a worldwide,
totally integrated PNT system of systems.

4. Where are we and where are
we going? “When” are we?

5. Stonehenge: a prehistoric
solar “clock”

6. Obelisks in ancient Egipt

7. Sundials in ancient Rome

8. Water and sand hourglasses

9. The Antikitera astronomic
calculator (150–100 B.C.)

10. Medieval clocks (1/2)

11. Medieval clocks (2/2)

12. Cristoforo Colombo, a genius
in navigation
Compass, speed log,
hourglass, observation of
the stars and sun,
knowledge of currents and
winds, and a meticulous
care in the compilation of
the logbook were for many
centuries the basis of the
"estimated navigation"
("dead reckoning"). A
brilliant user of this
technique, as it is clear
from reading the chronicles
of his journeys, was
Cristoforo Colombo.

13. Galileo and the isochronism of
the pendulum
Galileo Galilei

14. Christiaan Huygens and the
pendulum clock

15. Navigation & Timing: John
Harrison and the chronometer
1 second per day

16. Clocks accuracy evolution

17. The European GNSS: Galileo

18. Galileo FOC Satellites (OHB)

19. Galileo On-board Atomic
Clock (Selex ES)
"Passive Hydrogen Maser" (PHM): 1 second every 3 milion years!

20. GNSS: a Constellation of Ultra
Stable Clocks in the Sky

21. GNSS’s as a worldwide UTC
reference
UTC: UNIVERSAL TIME COORDINATED

22. Penetration of GNSS Devices

23. Multi-constellation GNSS
Timing Receivers

24. 5G: the next wave in mobile
communications

25. 5G infrastructure architecture

26. 5G, Internet of Things and
Timing

27. GNSS Timing: the GPS view

28. GNSS Timing and Critical
Infrastructures

29. The role of the European GNSS
Agency

30. Galileo Time Service Provider
(GTSP)

31. Galileo Timing Services

32. The European approach to a
Resilient PNT Infrastructure

33. Miniaturized Atomic Clocks

34. Worldwide System of Systems
Timing Infrastructure

35. Conclusion
• Our society has become essentially dependent on the world
Positioning, Navigation and Timing infrastructure, today
mainly based on GNSS’s;
• Many critical infrastructures would literally collapse in case
of a total, worldwide GNSS failure, mainly because of their
dependency on an exact timing reference;
• The European GNSS Agency (a.k.a. GSA) will play a vital
role in making the European GNSS Galileo more resilient,
service-oriented and interoperable with GPS;
• The development of non-GNSS solutions and of
autonomous platforms and technologies will lead to a
worldwide, totally integrated PNT system of systems, able
to resolve to a large extent all present limitations and
vulnerabilities.

36. Time is our only truly non-
renewable resource