Spectracom VelaSync 1225, User Manual

Page: 109 / 272

UTC : Coordinated Universal Time (Temps Universel Coordonné);
your local time zone determines the difference between UTC and
local time.
Note that UTC is not a time zone, but a time standard, i.e. it is not
used anywhere in the world as the official local time, whereas GMT
(Greenwich Mean Time) is a time zone that is used in several
European and African countries as the official local time.
TAI : International Atomic Time (Temps Atomique International).
The TAI time scale is based on the SI second and is not adjusted for
leap seconds. As of 26-Oct-2018, TAI is ahead of UTC by 37 seconds.
TAI is always ahead of GPS by 19 seconds.
GPS : The Global Positioning System time is the timescale maintained
by the GPS satellites.
Global Positioning System time is the time scale maintained by the
GPS satellites. The time signal is provided by atomic clocks in the
GPS ground control stations. The UTC–GPS offset as of 26-Oct-
2018 is 18 seconds.
For more information on Timescales, see "Timescales" below .
4.
If you want to override the system time with a manually set User Time , check
the Manual Time Set checkbox. For information, see "Manually Setting the Time"
on page 99 .
5. Click Submit to update the System Time and close the window.
3.2.1.2 Timescales
The System Time can be configured to operate in one of several timescales , such as
UTC, GPS and TAI
(Temps Atomique International)
. These timescales are based on
international time standards, and are offset from each other by varying numbers of
seconds.
When configuring VelaSync, in most cases, UTC will be the desired timescale to select.
Note: UTC timescale is also referred to as “ZULU” time. GPS timescale
is the raw GPS time as transmitted by the GNSS satellites (in 2018 the
GPS time is currently 18 seconds ahead of UTC time. UTC timescale
observes leap seconds while GPS timescale does not).
3.2 System Time
CHAPTER
3
•
VelaSync User's Manual Rev. 3 97