Infrastructure dependancy on GPSgreenspun.com : LUSENET : TimeBomb 2000 (Y2000) : One Thread
Does any one know how dependant our "Critical Infrastructure" is on the GPS time signals and what impact it might have once the roll over occurs?
P.S. It is my opinion that the GPS roll over date will start the trigger effect if Utilities and Telecom are are not ready for the roll over.
-- Ron (firstname.lastname@example.org), December 10, 1998
I don't see why the GPS rollover would have much effect on utilities or telecommunications. The "P" in "GPS" stands for "Positioning". It doesn't seem to me that much utility or telecom *operation* would benefit from GPS positioning.
(Perhaps GPS may be used in placement of new facilities or something. Can anyone describe a way that an electric, gas, telecommunications, water or other utility would use GPS in *operation* -- i.e., delivery of its product to customers?)
Time signals transmitted by GPS satellites are used in position calculations. As I understand it, the basic GPS rollover problem is that some receivers will not properly interpret times past the rollover moment when using them in position calculations.
-- No Spam Please (email@example.com), December 10, 1998.
GPS is also a highly accurate time source. Because receivers are comparatively cheap and very small these days, they can be used in a great many applications in which it is necessary to sychronize time events across a large number of widely distributed nodes. Data and event logging become much easier when your entire 'network' (of whatever devices) all agree on precisely what time it is.
Note that also, if you are not calculating position but only need to get highly accurate time data, then your receiver becomes much simpler - it typically only needs to track just one satellite instead of tracking three or more simultaneously when positional information is needed. The software is also much simpler - it doesn't need to concern itself with such arcane concepts as geometric dilution of precision (GDOP). It is ideal for distributed embedded systems which require a precise, coordinated time reference.
My point is that not all applications of GPS technology involve positional computations.
What I don't know is the full extent to which GPS is used solely as a time reference in (what those of us here would consider) 'mission critical' infrastructure. It's a fascinating subject and I wish I had more time to research it. I spent 4 years developing GPS applications for a defense contractor in the latter 80's - all of those did involve positional calculations. I've not followed it closely since then but it's hard to missing the fact that the usage of GPS has grown steadily. We used to joke a bit about the day everyone's wristwatch would be synchronized by GPS...
-- Arnie Rimmer (Arnie_Rimmer@usa.net), December 10, 1998.
Okay, I get it. Thanks, Arnie.
-- No Spam Please (firstname.lastname@example.org), December 10, 1998.
UMMMMM, To START with, all International Bank transfers are time/date stamped using GPS data (or so I'm reliably informed but can't remember the exact source).
Many international communications are GPS stamped for authenticity.
-- Chuck a night driver (email@example.com), December 10, 1998.
The GPS sets position but it also has a very dependable frequency it sends out. I know the telephone industry and the electric industry used this signal to synchronize to ( high speed data transmission and power frequency).
-- Mike (firstname.lastname@example.org), December 10, 1998.
There are several threads on GPS on Rick Cowle's EUY2K forum. You might want to start with this one
-- Chris (email@example.com), December 10, 1998.
Mike - it works the other way around. The super-high accuracy of the of the output frequency from each satellite is used inside the various GPS programs with the super-high accuracy of the timimg signals between ground stations and every satellite to let a remote unit calculate its position.
The change in received frequency as each satellite passes overhead (due to doppler shift) is part of the equation.
Ground stations -> can anybody spell "possible power outage on the earth side"?
-- Robert A. Cook, P.E. (Kennesaw, GA) (firstname.lastname@example.org), December 10, 1998.
This is a link with a very comprehensive explanation.
-- Mike Lang (email@example.com), December 10, 1998.
For what it's worth... some weeks ago I ran across this site: Welcome to the Navstar GPS JPO Y2K homepage. (Some of the links here are privileged access.) It seems to cover the ground unequivocally as to military GPS applications. Civilian GPS users are encouraged to query the manufacturers of their systems.
From SUMMARY STATUSAll JPO-procured receivers are Y2K/EOW compliant; All GPS satellites are Y2K/EOW compliant; Satellite ground support systems are not Y2K compliant; Control Segment is not Y2K/EOW Compliant; Rollover test plan and facilities available to all DoD; GPS JPO is widely publicizing both problems; GPS performance on schedule for EOW/Y2K compliance; check details in Y2K briefing.
From Y2K / EOW ROLLOVER ISSUES:Year 2000 rollover may cause a "crash" of a receiver/system; Rollover occurs 0000 hrs UTC 31 Dec 1999 / 01 Jan 2000; Year 2000 becomes "00" for programs using two digit year display-- may be interpreted as "1900" if used in calculations-- may be treated as an invalid date; GPS End of Week (EOW) Rollover may cause a "crash" of a receiver/system; Rollover occurs 23:59:47 hrs, 21 Aug 99; Improper account of the first epoch could cause an improper GPS time; GPS time based on epochs of 1024 GPS weeks; GPS week rolls over from week 1023 to week 0000; Clearly documented in ICD-GPS-200, par 3.3.4 (b)
From: USER EQUIPMENT (Civil Receivers):The United States Coast Guard is the government liaison to the civil sector for GPS. Please visit their web site at http://www.navcen.uscg.mil/gps/geninfo/y2k/ for information on your receiver's Y2K/EOW compliance status. The government does not endorse any claims that the commercial manufacturers have made on their Y2K status.
From SPACE SEGMENT:All GPS satellites Y2K/EOW compliant; All satellite ground support systems fully operational 31 Dec 98; check details in Y2K briefing as of: 12/03/98
From USER EQUIPMENT COMPLIANT DoD RECEIVERS:Compliant: "Successful operations before, during and after the EOW and Y2K rollovers as applied to Receiver Test Plan Boundaries."
From CONTROL SEGMENT:Operational Y2K/EOW compliance Jan 99.
-- Tom Carey (firstname.lastname@example.org), December 10, 1998.
There are roughly 50 links to pages about GPS on Sharefin's Y2k Page. NOTE: Sharefin's page has hundreds of other links -- the GPS section is about 3/4 of the way down, in the right-hand column. Or do a find on "GPS".
-- No Spam Please (email@example.com), December 13, 1998.
You might all want to look at this also:
(sorry...I know zero about HTML, so you will just have to live with copy and paste)
-- Rick Tansun (firstname.lastname@example.org), December 13, 1998.