GPS Rollover Tonight

Planes don't rely on GPS by norton_I · 1999-08-20 04:31 · Score: 1

The FAA has not approved GPS units as a primary navigation instrument. Almost all planes use LORAN (Same idea, only the transmitters are ground based -- cheaper, more accurate, but not very useful if you aren't airborne). I don't know if that has any sort of rollover problems, though.

Re:Planes don't rely on GPS by Anonymous Coward · 1999-08-20 04:59 · Score: 0

Actually, a system using GPS for air traffic control is under test. The advantage is that every pilot would have a real time picture of where every nearby aircraft is relative to his, accurate to GPS standards.

Re:Hmmm... I thought this was in the specs... by Pope · 1999-08-20 04:32 · Score: 1

isn't that the rational behind a lot of Y2K problems?
"Oh, we know it exists, but by the time it really happens,
somebody else will have replaced all this old equipment."

--
It doesn't mean much now, it's built for the future.

Re:How do you determine longitude with pre-elec te by Anonymous Coward · 1999-08-22 09:29 · Score: 0

Your best bet for Longitude is Dead Reckoning from an established position of Latitude..With no timepiece you can get a really good position of Latitude at "" noontime with a sextant. The sights are taken at Local Apparent Noon (Lan) which varies according to Longitude. The technique is to track the sun up to its maximum altitude which occurs in the True South.With a close fix like this for Latitude your dead reckoning will get you there eventually.. Be carefull with Polaris...it varies about 1/2 degree in the course of one night..30 mins s= 30 miles (N). Youre more likely to hit a reef with poor Latitude rather than Long. if you have any idea of your last Longitude position a good DR will give you a fair approx. J

GPS/NDS by thor · 1999-08-20 04:34 · Score: 1

brings back memories from my CSOC days...

"golf ball" & r2d2 antennas - hp1000 .vs. sun 3/260's & 280's - GPIB

daily briefings with tight ass generals (lol) - working 11pm-7am - 1lt apodoca

tracking lightning strikes for NOAA

the look on some cpt/col's face when a lowly a1c tells them their bird is wobbling - priceless

the good ole days...

as i was
thor

Re:We just spent 100K to upgrade our antique GPSs by neo-templar · 1999-08-25 05:08 · Score: 1

i stand corrected.

--
-------------------------------------------------- ----- if man created god , and evolution created m

Re:Hmmm... I thought this was in the specs... by Anonymous Coward · 1999-08-20 04:47 · Score: 0

Hey! Don't forget, the earthquake in Turkey wasn't long ago either.... more prophecies, anyone?

Ha ha! Flooders can't fsck /. over anymore. Nyah! by Anonymous Coward · 1999-08-20 05:00 · Score: 0

It must suck to be you! (*smirk!*)

We just spent 100K to upgrade our antique GPSs by Anonymous Coward · 1999-08-20 05:15 · Score: 0

GPSi? Manufacturer did not say they would fail, but did not say they wouldn't either. So we upgraded.....

Re:The only thing affected is the almanac by Anonymous Coward · 1999-08-20 05:30 · Score: 0

Man are you complacent. I hope your not in charge of anything but your own ass.

off to the sporting goods store by Barbarian · 1999-08-20 05:31 · Score: 1

First, as some people noted, it's Saturday night.

I'm really tempted to be at a sporting goods/hardware store that sells GPS receivers, and be "looking at buying" a couple at 6 PM MDT tomorrow night (MDT = GMT -0600).

Re:Should I be worried? by Mike+A. · 1999-08-20 05:38 · Score: 1

Yes, but there were a lot fewer planes in the air too. :-)

On the other hand, other posters in this thread and elsewhere have pointed out that essentially no commercial airliners are relying on GPS.

So, if you must worry about flying on a commercial airliner, worry about some bozo with a haywire GPS blundering in front of your plane, not about your plane's own navigation. (And even that probably should be regarded as paranoia...)

--

--
Do I look like I speak for my employer?

How do you determine longitude with pre-elec tech? by Anonymous Coward · 1999-08-20 05:40 · Score: 0

Latitude is easy (in the northern hemisphere anyway). It's just the angle between Polaris and the horizon. But how do you figure longitude without relying on a timepiece (which may fail after months at sea)?

not if you're in Kansas... by Anonymous Coward · 1999-08-20 05:52 · Score: 0

me and pa ain't too much worried 'bout it, seeings as how the Board of Edumuhkashun just set us ferther back 'n that last week or so....

Re:THIS CALLS FOR A NEW /. ICON by Anonymous Coward · 1999-08-20 05:58 · Score: 0

a flamin' PC. so long as it's not a duck, with a mallet... hitting a computer...

ROLLOVER THIS! by Anonymous Coward · 1999-08-20 03:15 · Score: 0

FIRST!

i wanna see this,, by Malto · 1999-08-20 03:18 · Score: 1

Gonna have to turn mine on and check it out... I wanna see what happens.

Malto

*Tomorrow* night by xyzzy · 1999-08-20 03:18 · Score: 1

GPS rollover is tomorrow night (between Saturday and Sunday).

SECOND!!! by screeching+weasel · 1999-08-20 03:18 · Score: 0

oh well...

Y2K hysteria a good thing in some ways... by Robin+Hood · 1999-08-20 03:24 · Score: 1

Because of all the Y2K hysteria, at least something like this WILL be paid attention to. Instead of dismissing it as "Oh, so it'll show the wrong date, who cares?" some GPS-system owners may actually take this warning seriously and get their units checked out, or be sure to NOT be out navigating at midnight GMT Saturday. So in a weird, roundabout way, the Y2K hysteria may actually end up saving a few lives...
-----

--
The real meaning of the GNU GPL:
"The Source will be with you... Always."

Worst Case Scenario by TrevorB · 1999-08-20 03:19 · Score: 1

Worst thing that could possibly happen with the GPS rollover... The classic Y2K misnomer: A plane falls out of the sky.

I don't think it would matter if it was a technicality (really bad weather, etc). The millenial panic level (which seems a bit subdued to me so far) would take a big jump, regardless of the fact that GPS and Y2K are completely seperate problems.

I also don't see too many people stocking up on compasses and sextants...

Re:No, it's tomorrow. by Russ+Steffen · 1999-08-20 03:25 · Score: 1

Argh. I guess I just repeated the link at in the story, but my point was the link cleary states that the rollever happens on 21-22 August, not 20-21 August.

Not just a cosmetic problem by gorilla · 1999-08-20 03:19 · Score: 1

More importantly that the date being wrong, the date is an essential part of the calculation which works out where you are. If the system isn't looking up the almanac for the correct date, it's not going to give you the correct location.

"Accuracy of navigation may also be severely affected" is an understatement. There will be no accuracy at all.

Should I be worried? by YeOldeGnurd · 1999-08-20 03:26 · Score: 1

I'm flying on Southwest at 0800 Eastern Standard Time (GMT + 0500?) Sunday morning.

Not to be paranoid, but do I have anything to worry about? It's a transcontinental flight, so they can't use Loran. Obviously, this is not a surprise to those in the aviation business, but I still worry a teeny bit flying on a cut-price carrier...

Bravery, Kindness, Clarity, Honesty, Compassion, Generosity

--
...Nothing interesting here. Just move along...

Re:Should I be worried? by drivers · 1999-08-20 03:31 · Score: 1

I wouldn't worry. What's the worst that can happen? :)
Re:Should I be worried? by TrevorB · 1999-08-20 03:33 · Score: 1

GMT+5h? Don't worry, if it's an issue, they'll see it first and the plane won't even be allowed off the ground...
Re:Should I be worried? by Russ+Steffen · 1999-08-20 03:35 · Score: 1

It shouldn't be a concern. When the FAA Ok'd GPS for IFR equipment, part of the testing that GPS manufacturers had to perform was for proper handling of the EOW rollover. And there are only a handful of IFR certified aircraft that use GPS as the only means of radionavigation, and I don't think that there are any in commercial service. Your airliner will most likely be using standard VOR/DME (VHF omnidirectional radio/distance measuring equipment) for navigation, and GPS only as a backup.
Re:Should I be worried? by Anonymous Coward · 1999-08-20 03:35 · Score: 0

I wouldn't be worried. I'm a pilot, and the national (US) carriers use VOR navigation much more than GPS. In addition, all commercial airline flights are monitored by air traffic control, who get alerts about air traffic getting too close, and can guide planes to their destination via headings watching their radar.
Re:Should I be worried? by Anonymous Coward · 1999-08-20 11:12 · Score: 0

Even less of a worry - If GPS is the backup either it is already certified for the rollover, or else the Minimum equipment list isn't current and the airplane is grounded.
there maay be some unhappy part 121 (charter) operators over this - but it would be their own damn fault. Frankly I doubt if it will be any problem at all.
Re:Should I be worried? by Octal · 1999-08-20 03:50 · Score: 1

Well, most GPS systems were designed with this and other roll-overs in mind, and chances are very slim that they will fail. Also, you still have map and compass, gyroscope, and radio to fall back on.

Believe it or not, airlines actually flew without falling out of the sky before GPS. :)
Re:Should I be worried? by palerider · 1999-08-20 04:10 · Score: 1

Southwest has the best safety record of any airline, last time I checked.

not till tommorrow by Anonymous Coward · 1999-08-20 03:21 · Score: 0

the GPS rollover happens tommorrow Saturday, August 21 when it rolls over to 12:00 am Sunday, August 22.

No, it's tomorrow. by Russ+Steffen · 1999-08-20 03:22 · Score: 1

Subject says it. The GPS EOW rollover happens midnight UTC, tomorrow - not tonight. More info here.

W2**10 bug by rde · 1999-08-20 03:34 · Score: 2

Which is more aesthetically pleasing; calling it a W2**10 bug or W2^10 bug? Or W1K bug, perhaps? Or Just WK?
A while ago I attempted a humourous web page, part of which enumerated some of the ways that tech was going wrong; I was surprised that my research research dug up so many ways that technology we relied on is fundamentally flawed. It seems that there isn't a technology out there that doesn't feature a fatal flaw that'll kill us all a few years hence.
It's got to the stage where I'm thinking of heading for the hills not because of Y2K, but because sooner or later something electronic is going to kill us all.

Re:W2**10 bug by blahedo · 1999-08-20 04:05 · Score: 1

You enumerated a few, the ones I've heard most about; but these and many, many (, many, many) more are listed on J.R. Stockton's ``Critical Dates'' site... all sorts of critical dates, mostly relating to rollover dates of various sorts, and mostly clustering around this era (of course). He appears to have updated it just this week, too.

--
``This, too, shall pass.'' ---Eastern proverb
Re:W2**10 bug by seajaycj · 1999-08-20 04:29 · Score: 1

hey, don't go getting all paranoid now!! Sure we can't handle the tech' stuff we have and sure more and more of it is being developed daily, with little or no controls in place to monitor its effects on people and the environment. Why should that bother anyone? Physical life is just an pause in the true dance anyways. I say, bring on the chaos!!

--
talk to ya, SeaJay

panic!!! by neo-templar · 1999-08-20 03:24 · Score: 1

wow! why didnt we see this coming!! where are all the gps bug programmers being hired and making small fourtunes when you need them!! this is in a way a good indicator on how much hype the y2k bug got versus this bug. now i know that the scope and affected areas is totally different, but it still is something to think about when it comes to pop computer culture (i hope your listening wired magasine and zdtv) and other various forms of sensationalist computer media (press coverage, not software)

--
-------------------------------------------------- ----- if man created god , and evolution created m

Groundhog's Day... by SMN · 1999-08-20 03:35 · Score: 1

Think of it like Groundhog's Day: If some GPS systems fail and there's a catastrophy, we'll have a bad Y2k, if nothing happens we'll have a good one.

--
-- Imagine how much more advanced our technology would be if we had eight fingers per hand.

Re:Groundhog's Day... by TrevorB · 1999-08-20 03:49 · Score: 1

Probably about as accurate too...

The GPS rollover is more likely to be the Y2K disaster scenario that your local newspaper is freaking out about. Navigation systems, electrical devices going nuts, etc.

I think Y2K will be more of an economic problem than an "elevators will get stuck". Programmed in a thousand different ways by a million programmers, the effects will be far more random and unknown. Probably enough to shake the JIT shipping philosophy up a bit.

OK, enough Y2K rant. All the people who've heard enough already can just go on being happy and keep their money in mutual funds before the Great Crash... ;)

Re:Thats not true. by Anonymous Coward · 1999-08-20 06:16 · Score: 0

No, it is very true. The GPS system relies on a series of almanacs to position the sats in the sky and other critical parameters to deducing a location. During the roll over they are ALSO changing this information. Any old reciever that cannot handle the new almanac data will basically be wrong

by the time it happens, old equip will be replaced by maphew · 1999-08-20 06:17 · Score: 1

heheh! Ain't that the truth. ;-)

(nice tag line btw)

Hmmm... I thought this was in the specs... by aressa · 1999-08-20 03:36 · Score: 1

The wording was kind of confusing on that page, but I thought that the GPS rollover (the modulo 1024 week field) was in the specs for the GPS system, and that if the receiver designers "cut the corners" and ignored this issue, it was their fault/problem.

I also read a while back that the biggest problem with this rollover would maybe cause problems in international banking due to the fact that some international banks use the GPS timestamp to coordinate electronic transfers. Sorry I don't have the references to these...

A

Re:Hmmm... I thought this was in the specs... by Anonymous Coward · 1999-08-20 04:07 · Score: 0

Worse than that, from an internet point of view (who cares about banks- its only money ;-), the internet/telecommunications infrastructure may suffer outages. Many of the Networks Elements out there get their time base off GPS. If they lose that, all kinds of crazy things may happen ranging from billing problems to outages. A lot of GPS receivers have a pivot point later than 1970 built in- these won't rollover for a few years or decades yet. The net as a whole aint going to die- but expect some bumpy times. Isn't this exciting? We get an eclipse and Y2K problems in just 2 short weeks ! Nostradamus MUST have been right! ;-)
Re:Hmmm... I thought this was in the specs... by blixco · 1999-08-20 04:20 · Score: 1

It's actually in the specs...part of the original military design and intent. Newer systems were suppossed to be in place by now.....

Re:How do you determine longitude with pre-elec te by PurpleBob · 1999-08-20 06:18 · Score: 1

Uh, get a lot of timepieces and hope one of them doesn't fail?

Well, you could do some complicated constructions with an astrolabe, a compass, and a really big chart of magnetic declinations. It'd probably be easier to reinvent electricity, though.
--

--
Win dain a lotica, en vai tu ri silota

We appreciate the news but... by maphew · 1999-08-20 06:22 · Score: 1

http://www.cnn.com/TECH/computing/9908/20/internet .theft/

We appreciate the news but...

you could have kept the message shorter, still got your message across, and not crossed the annoyance threshold.

Take it easy, news of this type will circulate very quickly.

-matt

Free Clue for Hemos! by Anonymous Coward · 1999-08-20 06:30 · Score: 0

This is your very own free clue. It has been decided that you are in need of a specific clue and, as such, you have been granted the privilege of receiving a clue free of charge. Please study the knowledge contained in your free clue with great care.

Do not use relative terms such as 'Tonight' when discussing chronological matters.

Use the term 'Tonight' when making a date with someone local, or procrastinating something.

Use absolute quanta such as the number of hours remaining before a significant chronological event. This eliminates the ambiguity of relative time zones for all readers.

This concludes the awarding of your free clue. Enjoy.

Wrong, Wrong, Wrongitty Wrong by ptomblin · 1999-08-20 06:32 · Score: 1

(to quote a good friend)

The FAA *has* approved GPS as primary navigation for enroute and non-precision approach. However, the testing for that FAA approval included proving that the unit could handle GPS_Week rollover.

But most planes don't use GPS or Loran for IFR navigation - they use ground based VOR navigation aids. So you don't have to know the latitude and longitude (as another person in this thread asked), you just follow the beam.

--
The next Cmdr Taco duplicate will be ready soon, but subscribers can beat the rush and see it early!

Re:How do you determine longitude with pre-elec te by TrevorB · 1999-08-20 07:29 · Score: 1

You DON'T.

That's what had naval navigation messed up for so long. It took the invention of a really good watch, a small pocketwatch, actually, to finally get accurate longitude.

This first watch used for such a purpose managed to make a transatlatic crossing while only loosing two seconds of time. Try taking a pendulum watch on a boat while the boat is rocking back and forth enough to make even the hardiest sailors ill...

Those first pocketwatches must have been the cell phones of the day. They were years ahead of their time, packed so much technology into such a little bundle, looked really cool and everyone had to have one.

Garmin by quadra · 1999-08-20 10:32 · Score: 1

Garmin.. one of the larger GPS makers claims all their GPSs will be ok. Some models may need to scan the sky again.. and a few need some software fixes.. overall not much to worry about.

Did it happen already? by um...+Lucas · 1999-08-20 10:59 · Score: 1

I was at the train station today after work, and one of the boards was blinking "RTC failed, system rebooting"... Naturally, i assumed it was linked to the GPS satelites in some way... now that it seems that the rollover doesn't happen til tomorrow, I'm thinking that the train authority switched their systems to NT or something...

GPS roll-over & Y2k by BugMaster+ChuckyD · 1999-08-20 03:36 · Score: 1

Most GPS units sold in past 3 or 4 years should be compliant. My Garmin GPS III is compliant (according to Garmin anyway) BTW its a nifty little nerd-toy complete with a scrolling zoomable map of the world with all of the major roads in the US on it, trip computer, compass (only works if you're moving), distance and heading to way points etc.

It will be interesting to see if the effect of the roll over is less than or greater than what is expected. If most newer GPS units are compliant as is claimed, and the negative effects are minimal, maybe the y2K compliance/impact predictions will also be accurate. We shall see.

Good thing I'm not playing Golf by GW+Hayduke · 1999-08-20 03:40 · Score: 1

I was going to try to go hit a few, but with the GPS Rollover, I'll lose the ability to track those lil buggers as I shank em off to the right :)
yeah OK -1 me allready

--
-- Life: Hate the Game... Love the cereal

Thats not true. by Anonymous Coward · 1999-08-20 03:47 · Score: 0

GPSes use deltas. The absolute date is irrelevent. Accuracy will only be potentially impared during rollover.

THIS CALLS FOR A NEW /. ICON by Anonymous Coward · 1999-08-20 03:51 · Score: 0

The GPS rollover could kind of get lumped in with other kinds of real or potential, serious or noteworthy tech related problems -- the next time eBay crashes, or on 9/9/99 when some obscure date-related problems crash corporate servers, there would be an icon for it.

I personally nominate the guy from BADDAY.MPG -- does anyone else have nominations?

Oregon student convicted under new ICT law... by Anonymous Coward · 1999-08-20 04:02 · Score: 0

http://www.cnn.com/TECH/c omputing/9908/20/internet.theft/

v

Blair Witch..? by Anonymous Coward · 1999-08-20 04:03 · Score: 0

Is this GPS malfunction the same sorta thing as what happened in The Blair Witch Project..? If so, maybe tonight'd be a good night to go see it. (Haven't seen it yet.)

ARGGHHH! by squarooticus · 1999-08-20 11:13 · Score: 1

Sprint PCS just went out for me in the Boston area. You gotta be shittin' me...
--
Kyle R. Rose, MIT LCS

--
[ home ]

NSA got all the Math Majors (no pun intended) by Mycroft-X · 1999-08-20 04:04 · Score: 1

"This means that the week count will roll over 7168/365.25 = 19.6249 years from then, or in 1980+19.625 = 1999.638 (August 21, 1999)."

Ok, by my reasoning:

1980
+ 19.625
---------
1999.625

Where does 1999.638 come from?

Mycroft

Re:NSA got all the Math Majors (no pun intended) by David+F. · 1999-08-20 04:21 · Score: 1

Well, the missing .013 comes from the fact that GPS time "began" on January 6 1980, not January 1. So, Their math is correct, but they should have noted it as

1980.013
+19.625
--------
1999.638

--
---- Dave
Re:NSA got all the Math Majors (no pun intended) by Russ+Steffen · 1999-08-20 04:25 · Score: 1

Umm... No. GPS Week 0 started 7 January 1980, not 1 January 1980. That's where the extra comes from.

Re: Yes, you can fly an aircraft without GPS! by ikluft · 1999-08-20 13:06 · Score: 1

Navigation of an aircraft can use any of a number of methods. If the GPS on board an aircraft goes out for the EoW rollover, these other methods are still available to the pilot, who will continue to fly the plane without GPS...

Follow landmarks on an aviation map. (Ever heard the saying "I follow roads?" That's not what IFR stands for. :-)
Fly a compass heading with a wind correction angle.
Tune in a "non-directional beacon" (NDB) radio transmitter and use direction-finding equipment in the aircraft to measure the relative direction from the plane to it. (It's old but it still works.) These transmitters are on the maps.
Tune in a "VHF Omnidirectional Range" (VOR) radio transmitter and use a VOR receiver in the plane to measure the compass direction from the station to the plane. (Almost every US aircraft has at least one VOR receiver.) These transmitters are on the maps too.
Receive signals from LORAN ("Long Range navigation") transmitters. This is as good as GPS when the upper-atmospheric conditions are good to bounce the signals long distances to you. (It propagates like a shortwave or HF Ham Radio.)
Ask for vectors (headings to fly from your current position) from air traffic control.

In other words... If the GPS fails, the pilot will keep flying the plane just like before there was GPS (which wasn't that long ago.) At the very worst, someone somewhere might get lost and land at the nearest/wrong airport.

If you want to know more about this, stop by your nearest General Aviation airport and ask a flight instructor. Depending on the airport, they can probably arrange to take you on an inexpensive introductory flight or flying lesson, just so you can see what it's like to fly an airplane. Some people get hooked after one time taking the controls...

(Yes, I'm a Private Pilot.)

Re:Building your own GPS/PC cable by Anonymous Coward · 1999-08-20 20:30 · Score: 0

I've got a Garmin GPS, and I haven't done it yet, but it musy be supereasy to build your own cable---only 4 conductors in the GPS's socket, 2 of which have to be power. If you plug the thing in your serial port, there's not much choice as to what the other 2 wires are going to have to be.

Now, if only I can find alligator clips small enough :)

Incidentally, my Garmin GPS has had a date problem for several months now, and has reverted back to 1980 sometime. It doesn't screw up the position or (apparently) the satellite tracking, only the date function and the time of sunset/sunrise. I thought the date rollover had already occured. Guess I've got some other problem. Hopefully if I build my cable and download the firmware update everything will be hunky-dory.

Re:The only thing affected is the almanac by ptomblin · 1999-08-20 21:32 · Score: 1

Actually, the 15 minutes to reload the almanac isn't a limitation of the GPS, it's a limitation of the satellites. The entire almanac is only broadcast in little packets that take 15 minutes to download the whole thing.

--
The next Cmdr Taco duplicate will be ready soon, but subscribers can beat the rush and see it early!

GPS Watch here in Kadena, Japan by Anonymous Coward · 1999-08-20 22:07 · Score: 0

Heh... interesting. At least now I know why I'm here... I'm workin' a 12 hour shift here at the Base Network Control Center on Kadena AFB, and my only duty is to make sure the GPS clock on the wall doesn't hit all zero's ('cept at midnight, just about 5 minutes ago here). At least I didn't have to wear my uniform in to work :)

Spauldo da Hippie

Re: Yes, you can fly an aircraft without GPS! by la8pv · 1999-08-20 23:35 · Score: 1

In comercial airlines they normaly use another sytem for navigation called inertial navigation system. Mainly this systems is used for long range fights as the ones done over the Atlantic ocean. Normally all the aircrafts prepared for long range flights use GPS and the Inertial navigation System. This system is compose by a inercial platform, tree acelerometers and one real time integration system which calculates the real aircraft position.

Radio interview by GRW · 1999-08-21 00:58 · Score: 1

I heard the fellow interviewed on CBC Radio's As It Happens program. He said that he already had a modern pc, but that he used the Altair for a lot of boilerplate legal forms that would have taken him too much time to convert to a modern program. Since the Altair was working satisfactorily, there was no reason to take the trouble to port the stuff over. With this new computer from Dell, he says he now has too many computers.

Why do people post what they don't really know? by Anonymous Coward · 1999-08-21 03:31 · Score: 0

Planes do use GPS. There are GPS approved IFR navigation systems. Also note that GPS was only approved on recent units which (with all the Y2K buzz) are almost certainly GPS Rollover compliant. They are not however the ONLY form of navigation. I do not know about commercial planes in the case of GPS being approved to fly on any gps but privte IFR can be flown on GPS. In your typical commercial airplane you have many navigation aids. You have VOR (Directional Radio Beacons) You have a Compass and Dead reconing if you really needed it. You have Gyroscopes (With give Lat and Lon in around the same accuracy as GPS) but they need recalibration at ever stop. I am unsure about Loran use on aircraft. Loran however is both less and mroe accurate. Loran is more repeatable than GPS. AKA you can get back to the same exact spot more accuratly. The problem is that loran uses lower frequencys which if you remember your physics course bend more easily. In certain places you can get huge errors but they will be the same ever time. I have seen 1 mile inacuracys in Loran. GPS will jump around but it will not get 1 mile off.

Rollover timing by quadra · 1999-08-21 07:11 · Score: 1

Was it just my GPS.. or did the week actually roll over to 0 a few seconds before the clock hit midnight?

good information by M-G · 1999-08-21 07:14 · Score: 1

Being a former employee of a major GPS manufacturer (I won't say which one...just that I got laid off because they were seriously in debt), I can tell you that the GPS design community is well aware of the week rollover problem. The problem isn't inherent in the GPS system itself, but rather in the specific units. The ground segment has the responsibility for handling local time....it doesn't really matter to the computation of satellite position. Some early units simply don't account for the rollover, so it's going to take them a while to figure out where they are.

Two good links about this:

http://joe.mehaffey.com/y2000dat.htm
http://joe.mehaffey.com/y2k-sv.txt

The only thing affected is the almanac by coyote-san · 1999-08-20 04:06 · Score: 2

Unless the GPS is particularly dumb, the only thing that should be affected by the rollover is that old, cheap units won't be able to use their internal almanac and the approximate date and location to quickly scan for the satellites. The date and location will be correct, but the birds won't be in the same position as they were 2^10 weeks ago.

Instead, they'll have to scan the entire sky for GPS signals and I'll reacquire my position after 20 minutes or so. I then need to leave the GPS running for a while so (pieces of) the new almanac can be downloaded; IIRC it's included in a low-bandwidth data channel. Or I can simply download the new almanac via a free program and a non-free PC/GPS cable. (I've ordered the cable, but with my luck they may be out of stock. :-)

Aviation and marine units, unlike hiking units, usually have far better antennas and they should be able to perform a "where in the heck am I?!" search much faster. Aviation units, in particular, will already be updated since they must periodically load new aviation databases containing the location of airports, VORs, etc.

--
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken

71 comments