jim.grubs@w8grt.fidonet.org (Jim Grubs) (01/28/91)
> From: michael@vk2bea.UUCP (Michael G. Katzmann) > Date: 25 Jan 91 14:09:22 GMT > Organization: Broadcast Sports Technology., Crofton, MD > Message-ID: <846@vk2bea.UUCP> > Newsgroups: rec.ham-radio,sci.electronics,sci.physics > > Has anyone noticed a degradation of the Navstar GPS system since the > outbreak of unpleasentness in the middle east? > > The implication, when GPS was first started, was that during times of > crisis the C/A code would be degraded so that an enemy could not use it. > > Does differential GPS totally get around this, or is there a trick > they can use to defeat this technique? Jeepers, Michael, why don't we just invite Saddam to sit in on JCS planning sessions and be done with it? -- Jim Grubs - Support OPERATION DESERT STORM - the 9th Crusade! UUCP: ...!uunet!w8grt!jim.grubs INTERNET: jim.grubs@w8grt.fidonet.org
henry@zoo.toronto.edu (Henry Spencer) (01/29/91)
> > From: michael@vk2bea.UUCP (Michael G. Katzmann) > > Has anyone noticed a degradation of the Navstar GPS system since the > > outbreak of unpleasentness in the middle east? > > The implication, when GPS was first started, was that during times of > > crisis the C/A code would be degraded so that an enemy could not use it. The last word I heard was that accuracy had actually improved, because the US military forces in the Gulf are making extensive use of commercial Navstar receivers, while the Iraqis have little or no Navstar equipment, so the public-access code is being kept as undegraded as possible. In article <1154.27A2ECFD@w8grt.fidonet.org> jim.grubs@w8grt.fidonet.org (Jim Grubs) writes: >Jeepers, Michael, why don't we just invite Saddam to sit in on JCS planning >sessions and be done with it? Why bother? There is nothing secret about any of this. There is nothing to be gained, and a fair bit to be lost, by keeping the public in ignorance of things Saddam already knows. -- If the Space Shuttle was the answer, | Henry Spencer at U of Toronto Zoology what was the question? | henry@zoo.toronto.edu utzoo!henry
poynton@vector.Eng.Sun.COM (Charles A. Poynton) (01/29/91)
My understanding is that so many commercial-grade receivers have been pressed into service that they had to turn the commercial-accuracy-degrading codes OFF. C. ----- Charles A. Poynton Sun Microsystems Inc. vox 415-336-7846 2550 Garcia Avenue, MTV21-10 fax 415-969-9131 Mountain View, CA 94043 <poynton@sun.com> U.S.A. -----
marty@puppsr.Princeton.EDU (Marty Ryba) (01/31/91)
In article <1991Jan29.044137.20914@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes: |> The last word I heard was that accuracy had actually improved, because the |> US military forces in the Gulf are making extensive use of commercial |> Navstar receivers, while the Iraqis have little or no Navstar equipment, |> so the public-access code is being kept as undegraded as possible. A little deeper information: all the new GPS/Navstar satellites (so-called "Block II") have what is called SA, Selective Availability. SA allows the DoD to dither the effective phase and frequency in the pseudocode that contains the range information. I forget, but I think they are also allowed to lie a little about their orbits. Anyway, they can then add uncertainty in several places. Starting in April or so of last year, they turned on SA on the Block II satellites, but only part way: they just added about 100 ns pure white phase noise. So, if you had time to track for a while (say, if you are NIST and want to transfer atomic time accurately) you could get around this. The SA limits triangulation accuracy for positioning to about 100 meters, compared to 10 m or so with SA off. Note the few older Block I satellites still in operation have no SA capability; if you can control which satellite you talk to, you can get around it (until they launch enough new ones to retire the old ones). In August, when Desert Shield started, the DoD realized they needed Navstar stuff, but their military versions of the receivers are not yet ready, so they switched SA off. As Henry stated, this is little strategic loss, with much to gain (the commercial Navstar receivers are portable enough for infantry). If anything, I'd imagine the Iraqis may have some GLONASS equipment from the Soviets, if they trusted them enough. GLONASS is just as good as GPS (but I think the receivers are a little less portable). -- Marty Ryba | slave physics grad student Princeton University | They don't care if I exist, Pulsars Unlimited | let alone what my opinions are! marty@pulsar.princeton.edu | Asbestos gloves always on when reading mail
phil@brahms.amd.com (Phil Ngai) (01/31/91)
In article <1321@catnip.berkeley.ca.us> bandy@catnip.berkeley.ca.us (Gun Control is Hitting Your Target) writes: |So, Henry, how do you know that Saddam already knows this? Let's see, if Saddam doesn't have a GPS, it doesn't matter to him how accurate the GPS he doesn't have is. If he does have a GPS, it's not going to be hard to find out how accurate it is, assuming he knows the coordinates of at least one location he has access to. -- When someone drinks and drives and hurts someone, the abuser is blamed. When someone drinks and handles a gun and hurts someone, the media calls for a gun ban.
walvdrk@pttrnl.nl (01/31/91)
> This is somewhat off the subject, but - > > Why is everyone calling this guy by his first name? Is it to > avoid confusion with the king of Jordan (who seems also none too > friendly as well). Or is there a naming convention in that part > of the world that calls for it? Maybe just because there are even more "Hussain"s around there than there are "George"s around there? Kees van der Wal e-mail: JC_vdWal@pttrnl.nl ---------------------------------------------------------------------------- PTT Research Neher Laboratories P.O. Box 421 2260 AK Leidschendam The Netherlands Phone: +31 70 3326295 ============================================================================
henry@zoo.toronto.edu (Henry Spencer) (02/01/91)
In article <1321@catnip.berkeley.ca.us> bandy@catnip.berkeley.ca.us (Gun Control is Hitting Your Target) writes: >So, Henry, how do you know that Saddam already knows this? Because it's public information. If he doesn't know it, it's because he's not paying attention. Either he is, in which case telling him about it again hurts nothing, or he isn't, in which case he isn't going to notice it this time either. -- If the Space Shuttle was the answer, | Henry Spencer at U of Toronto Zoology what was the question? | henry@zoo.toronto.edu utzoo!henry
abeals@autodesk.com (Segments Are For Worms) (02/01/91)
phil@brahms.amd.com (Phil Ngai) writes: >In article <1321@catnip.berkeley.ca.us> bandy@catnip.berkeley.ca.us (Gun Control is Hitting Your Target) writes: >|So, Henry, how do you know that Saddam already knows this? >Let's see, if Saddam doesn't have a GPS, it doesn't matter to him >how accurate the GPS he doesn't have is. If he does have a GPS, >it's not going to be hard to find out how accurate it is, assuming >he knows the coordinates of at least one location he has access to. Well, Phil, let's see. Let's say that Saddam didn't have GPS... Then he [or one of his agents] reads Henry Spencer's article... Suddenly, someone buys a bunch of GPS units... And then ships them off to Iraq... So, Phil, now do you understand? -- Andrew Scott Beals abeals@autodesk.com
karn@epic.bellcore.com (Phil R. Karn) (02/01/91)
Don't forget that the region also has good Loran-C coverage from two permanent chains in Saudi Arabia. My own experience with the Northeast USA Loran-C chain has been repeatable accuracy of 20-40 meters; this is better than the 100 meter figure given for GPS with selective availability turned on. Furthermore, Loran-C is available 24 hours/day, unlike GPS which has coverage gaps. According to publicly available orbital elements and operational schedules, there is currently a daily gap in GPS coverage in the Baghdad area from about 1130 to 1200 UTC. (A gap is defined as fewer than 4 operational satellites visible simultaneously, including both Block I and Block II spacecraft.) Phil
gary@ke4zv.UUCP (Gary Coffman) (02/01/91)
In article <1991Jan30.232701.25602@amd.com> phil@brahms.amd.com (Phil Ngai) writes: >In article <1321@catnip.berkeley.ca.us> bandy@catnip.berkeley.ca.us (Gun Control is Hitting Your Target) writes: >|So, Henry, how do you know that Saddam already knows this? > >Let's see, if Saddam doesn't have a GPS, it doesn't matter to him >how accurate the GPS he doesn't have is. If he does have a GPS, >it's not going to be hard to find out how accurate it is, assuming >he knows the coordinates of at least one location he has access to. Even easier, if he has a GPS receiver, it's all explained in the manual. At least it is in the manuals for the ones we have. Gary KE4ZV
jim.grubs@w8grt.fidonet.org (Jim Grubs) (02/02/91)
> From: henry@zoo.toronto.edu (Henry Spencer) > Date: 31 Jan 91 16:57:57 GMT > Organization: U of Toronto Zoology > Message-ID: <1991Jan31.165757.19929@zoo.toronto.edu> > Newsgroups: rec.ham-radio,sci.electronics > > In article <1321@catnip.berkeley.ca.us> bandy@catnip.berkeley.ca.us (Gun > Control is Hitting Your Target) writes: > >So, Henry, how do you know that Saddam already knows this? > > Because it's public information. You're willing to endanger lives just to prove you have a right to shoot your mouth off anytime you choose? Being 'right' about abstract consitutional principles is not worth somebody's life. It would be different if you were gambling only YOUR life. You're playing games with someone else's life. -- Jim Grubs - Support OPERATION DESERT STORM - the 9th Crusade! UUCP: ...!uunet!w8grt!jim.grubs INTERNET: jim.grubs@w8grt.fidonet.org
koning@koning.enet.dec.com (Paul Koning) (02/02/91)
|> |>Don't forget that the region also has good Loran-C coverage from two |>permanent chains in Saudi Arabia. My own experience with the Northeast |>USA Loran-C chain has been repeatable accuracy of 20-40 meters; this |>is better than the 100 meter figure given for GPS with selective |>availability turned on. |> Repeatability isn't the same as accuracy. Is Loran-C really ACCURATE to the number you quoted? (The FAA writeup about it says otherwise.) paul PS. To Jim Grubs: Please SHUT UP.
nagle@well.sf.ca.us (John Nagle) (02/03/91)
The Trimble Navigation portable GPS receiver, a handheld device
intended for small boat navigation and available in boat shops, is being
used by U.S. troops. Trimble is manufacturing them as fast as possible,
but can't keep up with the sudden demand. They're made in here in Silicon
Valley. The militarized portable GPS receivers aren't available in
quantity yet, so this commercial unit is being pressed into service.
It's a cute little device. It takes about 30 seconds for it to get
a fix, it runs on batteries, and it's watertight. (It even floats.)
Trimble doesn't promise accuracy better than a few hundred meters,
though, so signal degradation for security reasons probably isn't
an issue.
John Naglefred@sma2.uucp (Fred Brooks) (02/03/91)
In article <1172.27A97FF9@w8grt.fidonet.org> jim.grubs@w8grt.fidonet.org (Jim Grubs) writes: > > > >So, Henry, how do you know that Saddam already knows this? > > > > Because it's public information. > >You're willing to endanger lives just to prove you have a right to shoot your >mouth off anytime you choose? Being 'right' about abstract consitutional >principles is not worth somebody's life. It would be different if you were >gambling only YOUR life. You're playing games with someone else's life. > Give us all a break. This info is everywhere and has been known for months. If you read IEEE Spectrum there have been several stories about it. I'm sure there are a few engineers in Iraq that subscribe. -- Defend your 2nd amendment rights. What is the New World Order? Fred Brooks Portland Oregon
bhoughto@pima.intel.com (Blair P. Houghton) (02/04/91)
In article <1172.27A97FF9@w8grt.fidonet.org> jim.grubs@w8grt.fidonet.org (Jim Grubs) writes: >You're willing to endanger lives just to prove you have a right to shoot your >mouth off anytime you choose? Being 'right' about abstract consitutional >principles is not worth somebody's life. It would be different if you were >gambling only YOUR life. You're playing games with someone else's life. Get a grip, Jim. Nobody's endangering anybody by discussing the capabilities of commercially-available electronic toys. The publishers of Jane's know far more about this stuff than we'll ever crowbar into a Usenet posting, and you can bet Saddam Hussein's been subscribing to Jane's since he was just a little dictator. Dangerous secrets are marked so you can't mistake them for common knowledge, and I haven't seen any of those here. Anyway, he probably knows the insides of every weapon we have, having got the info from the salesmen who work for the manufacturers of those weapons. It's also pretty apparent that he's completely incapable of anything resembling effective military activity, anyway. I don't think it will hurt us to let him know the exact coordinates of the target on which he's standing. --Blair "We should show him the battle plans for an upcoming amphibious assault on Baghdad. He'd send his boats to Israel for safekeeping..."
mcovingt@athena.cs.uga.edu (Michael A. Covington) (02/04/91)
Assuming the supply catches up with the demand and these widgets are available again, how much does a GFS receiver cost? I'd like to be the first on my block with satellite navigation in my car, maybe...
bhoughto@hopi.intel.com (Blair P. Houghton) (02/05/91)
In article <1991Feb4.062853.21374@athena.cs.uga.edu> mcovingt@athena.cs.uga.edu (Michael A. Covington) writes: >Assuming the supply catches up with the demand and these widgets >are available again, how much does a GFS receiver cost? >I'd like to be the first on my block with satellite navigation in >my car, maybe... About $3K. --Blair "Nobody ever said that knowing your exact position wouldn't affect your momentum..."
henry@zoo.toronto.edu (Henry Spencer) (02/05/91)
In article <1172.27A97FF9@w8grt.fidonet.org> jim.grubs@w8grt.fidonet.org (Jim Grubs) writes: > > >So, Henry, how do you know that Saddam already knows this? > > > > Because it's public information. > >You're willing to endanger lives just to prove you have a right to shoot your >mouth off anytime you choose? ... As your leader says, "read my lips: it's public information". Nobody is endangering anybody by discussing it in public, because it has *already* been discussed in public. -- "Maybe we should tell the truth?" | Henry Spencer at U of Toronto Zoology "Surely we aren't that desperate yet." | henry@zoo.toronto.edu utzoo!henry
abeals@autodesk.com (Segments Are For Worms) (02/05/91)
bhoughto@pima.intel.com (Blair P. Houghton) writes: >Anyway, he probably knows the insides of every weapon we >have, having got the info from the salesmen who work for >the manufacturers of those weapons. Uh huh. And "every good spy has a green badge". [or a red badge for LANL] You still don't publish the data. Since everyone else has the fab data for the '486, Blair, could you please publish it? Thanks. -- Andrew Scott Beals abeals@autodesk.com
waters@nddsun1.sps.mot.com (Mike Waters) (02/05/91)
In article <1172.27A97FF9@w8grt.fidonet.org> jim.grubs@w8grt.fidonet.org (Jim Grubs) writes: > > From: henry@zoo.toronto.edu (Henry Spencer) > > In article <1321@catnip.berkeley.ca.us> bandy@catnip.berkeley.ca.us (Gun > > Control is Hitting Your Target) writes: > > >So, Henry, how do you know that Saddam already knows this? > > Because it's public information. >You're willing to endanger lives just to prove you have a right to shoot your >mouth off anytime you choose? Being 'right' about abstract consitutional >principles is not worth somebody's life. It would be different if you were >gambling only YOUR life. You're playing games with someone else's life. I would be fascinated to know how information that has been published in everything from IEEE Spectrum to Sailing magazine could "endanger lives"? BTW those "abstract constitutional principles" have been responsible for a lot more good men dying than the entire allied casualties so far in this war! Maybe YOU don't think the U.S. Constitiution is anything more than a some abstract ideal, but some of us disagree. I would also draw your attention to the fact that Henry Spencer is in Canada which last time I checked was an independant country. If guns are banned how will Conservatives win arguments?
ts@cup.portal.com (Tim W Smith) (02/07/91)
Uh, I think what was objected to in the orignal posting was not discussing how GPS works and how accurate it is, but the request for how to get around limitations the military imposes for security purposes. That hasn't been discussed in IEEE journals and Sailing, has it? Tim Smith
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) (02/08/91)
In article <39009@cup.portal.com> ts@cup.portal.com (Tim W Smith) writes: >Uh, I think what was objected to in the orignal posting was not >discussing how GPS works and how accurate it is, but the request >for how to get around limitations the military imposes for >security purposes. >That hasn't been discussed in IEEE journals and Sailing, has it? Sure it has... Well, at least in Aviation Week. The US Govt has been advertising GPS as good for civil use, then reserving the right to degrade the signal. The recommended way (as seen by civil airlines) to improve accuracy is to use GLONASS, the Russian system, which the Russians promised not to degrade. [let's see how effective Mr. Grubs' rantings are at keeping GLONASS secret from the Iraqis...] Marc Kaufman (kaufman@Neon.stanford.edu)
henry@zoo.toronto.edu (Henry Spencer) (02/08/91)
In article <39009@cup.portal.com> ts@cup.portal.com (Tim W Smith) writes: >Uh, I think what was objected to in the orignal posting was not >discussing how GPS works and how accurate it is, but the request >for how to get around limitations the military imposes for >security purposes. > >That hasn't been discussed in IEEE journals and Sailing, has it? Sure it has. Maybe not in sailing, but in the IEEE journals and Aviation Week. There are plenty of potential Navstar users, notably the aviation people, who badly need high accuracy and don't like DoD being able to degrade their navigation aids without warning. Those people have been very interested in ways around the problem, and much has been published on the subject. -- "Maybe we should tell the truth?" | Henry Spencer at U of Toronto Zoology "Surely we aren't that desperate yet." | henry@zoo.toronto.edu utzoo!henry
waters@nddsun1.sps.mot.com (Mike Waters) (02/09/91)
In article <39009@cup.portal.com> ts@cup.portal.com (Tim W Smith) writes: >Uh, I think what was objected to in the orignal posting was not >discussing how GPS works and how accurate it is, but the request >for how to get around limitations the military imposes for >security purposes. > >That hasn't been discussed in IEEE journals and Sailing, has it? Interestingly enough it HAS been! (I pick my examples carefully you know - GOTCHA! :-) ) IEEE Spectrum about 18 months ago featured a debate about the wisdom of ncrypting parts of the information. THey drew analogies to WW II navigation aids which were generally left in place because their removal caused more problems to our side than aid to the enemy (we used them a LOT more :-) ) THey also described several techniques for defeating the encryption indirectly. (I.e. not by breaking the code). THe closing comment was an about a reporter who asked a Soviet Military Attache about the possibillity of their using GPS to target missiles. The response was essentially "You must be joking. THats the dumbest thing we could ever do!". All with far more circulation than Usenet! Sailing magazine had a writeup on some methods to use GPS in a harbour provided you has a reference point. THe "fuzzing" only destroys ABSOLUTE accuracy, not relative accuracy according to their article. 73 Mike AA4MW -- *Mike Waters AA4MW/7 waters@dover.sps.mot.com * ** If guns are outlawed, how will conservatives win arguments? **