Difference Between GPS Time and UTC
Robert Holloway
seconds offset from UTC and is currently 9 seconds different. Can
someone confirm this, which is ahead and which is behind and where is
this information published?
Robert Holloway
email: holl...@wantree.com.au
|======================================================================
| Robert David Holloway
| email: holl...@wantree.com.au
| Tel: +619-271-9594
| Fax: +619-344-8783
|
|====================================================================
Allen Miller
Robert Holloway <holl...@wantree.com.au> wrote:
>I understand that GPS time is, by definition, an integer number of
>seconds offset from UTC and is currently 9 seconds different. Can
>someone confirm this, which is ahead and which is behind and where is
>this information published?
This is from http://tycho.usno.navy.mil/leap.html :
LEAP SECOND ALERT!
U.S. NAVAL OBSERVATORY
WASHINGTON, DC 20392-5420
August 2, 1995
No. 57
TIME SERVICE ANNOUNCEMENT SERIES 14
UTC TIME STEP
1. The International Earth Rotation Service (IERS) has announced the
Introduction of a time step to occur at the end of December 1995.
2. Coordinated Universal Time (UTC) will be retarded by 1.0s so that the
sequence of dates of the UTC markers will be:
1995 December 31 23h 59m 59s
1995 December 31 23h 59m 60s
1996 January 01 0h 0m 0s
3. The difference between UTC and International Atomic Time TAI is:
from 1994 Jul. 1, 0h UTC, to 1996 Jan. 1, 0h UTC: TAI-UTC = +29s
from 1996 Jan. 1, until further notice: TAI-UTC = +30s
4. The insertion of one leap second will be evident by the change of
sign of the DUT1 correction which will become positive. Extrapolated
values of DUT1 are distributed weekly in the IERS Bulletin A (Time
Service Announcement Series 7).
5. All coordinated time scales will be affected by this adjustment.
However, the Loran-C, GPS and OMEGA systems will not be adjusted
physically. Times of Coincidence (Time Service Announcement Series 9)
will be issued for Loran-C. For GPS, the leap second correction
contained within the UTC data of subframe 4, page 18 of the navigation
message transmitted by the satellite will change.
Before the time step the leap second correction will be:
GPS-UTC = +10s (i.e., GPS is ahead of UTC by ten seconds).
After the time step the leap second correction will be:
GPS-UTC = +11s (i.e., GPS will be ahead of UTC by eleven seconds).
The OMEGA Reference Ephoch (ORE) will change - that is, from 1 Jan.
1996 (after the leap second) the OMEGA system will operate with the
the beginning of segment one on seconds 40, 50, 00, 10, 20, and 30 of
each minute.
DENNIS D. MCCARTHY
Acting Director
Directorate of Time
--
Allen Miller PP-ASEL KB0NDD mil...@lamar.colostate.edu
Allen Miller
Allen Miller <mil...@polaron.physics.colostate.edu> wrote:
Sorry to follow up to my own message. As the preceeding message says,
the time broadcast by the GPS satellites doesn't change when the do a
leap second, but they do broadcast a correction factor. I've got my
Magellan GPS2000 here right now, and the time it is displaying is
within +/- 1 second of the "real" time as reported by the Naval
Observatory.
Al
Scott P. Cryan
The actual difference between UTC and GPS is 10 seconds. It
will be 11 seconds on Jan 1, 1996. Consult the IERS bulletin
which is at http://maia.usno.navy.mil/direct.html
Hope this helps
--------------------------------------------------------------------
Scott P. Cryan McDonnell Douglas Aerospace
Phone: (713) 244-4008 Mail Code MDC2-4433
Fax: (713) 244-4419 13100 Space Center Boulevard
e-mail: cr...@pat.mdc.com Houston, Texas 77062
Harlo Peterson
(Robert Holloway) wrote:
>I understand that GPS time is, by definition, an integer number of
>seconds offset from UTC and is currently 9 seconds different. Can
>someone confirm this, which is ahead and which is behind and where is
>this information published?
Check out http://tycho.usno.navy.mil/time.html for a lot of time
information from the official keepers of time for the US. One of the
pointers in the page http://tycho.usno.navy.mil/leap.html describes the
current number of seconds difference between UTC and GPS time and what the
difference will be after Dec 31, 1995.
From the page:
Before the time step the leap second correction will be:
GPS-UTC = +10s (i.e., GPS is ahead of UTC by ten seconds).
After the time step the leap second correction will be:
GPS-UTC = +11s (i.e., GPS will be ahead of UTC by eleven seconds).
Lots of other good stuff here for the interested.
--
Harlo Peterson Digital Equipment Corporation
pete...@specxn.enet.dec.com 305 Rockrimmon Blvd South (CXO3-1/E9)
+1.719.592.5124 Colorado Springs, CO 80919-2398
dgbu...@iceman.raleigh.ibm.com
|> I understand that GPS time is, by definition, an integer number of
|> seconds offset from UTC and is currently 9 seconds different. Can
|> someone confirm this, which is ahead and which is behind and where is
|> this information published?
|>
Mark Fellhauer
>In article <45bnd2$7...@polaron.physics.colostate.edu>,
>Allen Miller <mil...@polaron.physics.colostate.edu> wrote:
>Sorry to follow up to my own message. As the preceeding message says,
>the time broadcast by the GPS satellites doesn't change when the do a
>leap second, but they do broadcast a correction factor. I've got my
>Magellan GPS2000 here right now, and the time it is displaying is
>within +/- 1 second of the "real" time as reported by the Naval
>Observatory.
My Trailblazer XL usually "syncs" with a WWV signal taken off
shortwave to within about a tenth of a second!
Note: the time display shown on the "location" screen of Magellan
GPS (and others) is the time when the last fix was aquired and NOT
current time. Actual time is displayed in the "Setup" window.