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New GPS Standard Published 111

Posted by michael
from the dont-need-no-stinking-directions dept.
jeffy124 writes: "The Dept of Defense has released a new standard for GPS. The new standard will go into become available for use starting in 2003 when the first satellites are launched. Full completion is estimated to 2014. The new standard allows for greater horizontal accuracy of 36 meters instead of 100 meters, and also sets a new baseline for transmission protocols that circumvent ionic interference."
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New GPS Standard Published

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  • the GPS does not line up with genwich so are all the maps wrong in the world (excempting US which contain the error)

    or is GPS wrong

    (-;

    standards

    regards

    john jones
    • by epsalon (518482) <slash@alon.wox.org> on Sunday October 21, 2001 @08:52AM (#2456167) Homepage Journal
      Actually, it does line up.
      In greenwich they have museum about longitude measurment, and they have there a GPS device (turned on) and it shows almost 000 latitude (almost because it's a few meters away from the line itself).
      • Just what is "a few meters?" They're a little farther than that from the equator.

      • It's all a matter of datum, I think. I've been down to Greenwich with a GPS-12 and stood on the line, and it was shown as being just slightly off. Maybe 13 seconds or something -- can't remember, as my GPS with the waypoints concerned is at home.

        The GPS displayed zero about 30m west of the line. Of course, this might all just be a matter of measurement accuracy, and a matter of the datum in use. Not enough of a difference to worry about, anyway...
    • They are both right in a way. Any global map coordinate system depends on a reference elipsoid (aka squashed sphere) that approximates the Earth's surface and a reference meridian which determines where zero longitude is on the elipsoid. This is known as a "datum". The one used by GPS is known as WGS84. The WGS84 elipsoid is defined in such a way that the average movement of the Earth's surface due to plate tectonics is zero wrt the coordinate system.

      Maps in the UK traditionally use a datum set up by the Ordnance Survey (known as OSGB36) which uses a different elipsoid and results in a disagreement between a GPS receiver and an OS map of about 100 metres unless you change the datum used by the GPS receiver to agree with the map.

      In fact due to the movement of the Earth's crust, the whole of Great Britain is moving North East wrt WGS84 and so the Greenwich meridian is actually getting further away from the meridian as shown on a GPS receiver.
  • by Anonymous Coward on Sunday October 21, 2001 @08:47AM (#2456158)
    NOW, obviously for military usages. "The new standard allows for greater horizontal accuracy of 36 meters instead of 100 meters, and also sets a new baseline for transmission protocols that circumvent ionic interference" -- now this all wrong, SlashDot editors READ YOUR STORY, it clearly says - "DoD, as operator of the GPS, now provides civil users a horizontal positioning accuracy of 36 meters, compared to 100-meter accuracy in the previous edition of the standard, which was published in 1995. ". NOW, not in the NEW standard.
    • A long term friend of mine makes his living as a solo gold miner. Despite these artificial limitation posed by the the US and Australian DoD, apparently everyone who's wanted to has been able to get accuracy to within fifteen meters for quite some time now.

      Unfortunately, I'm not too sure on the specifics whic hallow this. Do the sattellites give bad readings which can be easily re-set to their true value, is some kind of interpretarion of multiple results possible (a kind of triangulation)? Either way, this has been the case for over five years.
      • Unfortunately, I'm not too sure on the specifics whic hallow this. Do the sattellites give bad readings which can be easily re-set to their true value, is some kind of interpretarion of multiple results possible (a kind of triangulation)?

        From what I understand the low bits have some noise added to them. The noise is an encrypted stream, so a military GPS with the key can reproduce the noise and cancel it out.

        Other GPSes have a few choices. If you sit in one place and avg together all the samples you get a value that converges on your real location (because the noise is more or less random, if it were fixed this wouldn't work, but something else would!). You can also use two GPSes, but I kind of forget exactly how this works. I *think* you keep one at a fixed point, and have it broadcast the delta between it's known position and the position that is being broadcast, your mobile GPS uses that delta to find the real location (this may only work if you are looking at the same satellites)

        • by Tungz10 (99857)
          The noise you refer to is known as Selective Availability (SA). It's an error that drifts over time. I believe it takes about a day to average it out exactly. Also, the DOD turned off SA a few years ago. Although with recent events it may be turned back on again if it hasn't already.

          Now the error is the same for the same general area. So you can leave one gps at a known location and carry a second gps around with you. From the first GPS you transmit the error (you know where you are and you know where it says you are, you transmit the difference). And then subtract that error from the second gps to get extremely good accuracy. This is known as Differential GPS and I think it can achieve accuracy to about a meter.
      • It's called Differential GPS (DGPS). (GPS is already triangulation of different signals sources)
        AFAIK, the signals are delayed according to a certain algorithm (known to the DOD).
        But there are several fixed GPS receivers which compare the measured position and the real position. The comparision yields a correction factor for the various signals from the different GPS-satellites.
        Here is some short explanation [trimble.com]
      • I designed a program a little while ago which tracks big slabs of steel placed in stacks of 10 slabs high on one big 'parking lot' at a steelfactory. Cranes roll around the lot moving around slabs, controlled by orders given from a server. Each slabs GPS-location and position in it's pile is stored on the servers DataBase. The crane sends the current weight in it's grabbingthinghy to the server which then calculates how many slabs are picked from which pile.

        But back to he point, those cranes are accurate to 5 metres/15 feet. See how GPS works [howstuffworks.com] more information. This page only leaves out on thing. They state you need 3 satelites to make out your position. They don't mention that it's posibble to make calculations with more than 3 satelites. In that case you end up with several position with which the actually position is interpollated. This works quite well because on most places on earth you receive signals from 4 or 5 satelites which means you don't get 1 position but 2 or even 3.

      • No.. they can't be easily re-set to their true value; otherwise, there would be no point.

        It's some noise in the low-order bits to introduce some added error.
        It's been removed, as of last January, I thought. It was known as 'selective availability' or 'sa'. See, sometimes GPS MIGHT be really accurate, but not always.

        Surveryors, etc, use DGPS (Differential GPS) where they use a GPS receiver at a known, precise location, so they can calculate the error being introduced by the satellites in question so they can get more accurate readings. It works very well.

        The main reason that precision readings without DGPS are dangerous, I read, is because of mid-course corrections for ballistic missiles.... you see, to change the target, you change direction halfway through, way up in the air... at the top of your arc. A small margin of error at this level makes a huge margin of error on the ground.
        • After doing a lot of research on the net regarding GPS (having purchased one a few months ago) I'd like to comment on what you've said. DGPS only gets about 3-5meter accuracy (95% of the time, or some such statistic). DGPS is used to counter selective availability and some of the distortion caused by various atmospheric conditions. Survey units use a more robus version which actually gives them only distance from a specific point. (A very precise point mind you). If you know where that point is located very accuratly you can convert the data to get precise locations. Unfortunatly there are a large number of errors which have to be accounted for and the results for survey units look bizzar.

          The really cool thing is, if you have 2 garmin units you can post-process the information later and get a very similar level of accuracy. But again, it is only as good as the set point you started with.
          • DGPS only gets about 3-5meter accuracy (95% of the time, or some such statistic). DGPS is used to counter selective availability and some of the distortion caused by various atmospheric conditions. Survey units use a more robus version which actually gives them only distance from a specific point. (A very precise point mind you).
            Actually, DGPS is old news. Before that, you could do post-processing of the data from a base station receiver over a known position & another receiver. DGPS addded telemetry to each receiver, but you still had to sit at a point for 15-30 min to get 1 m accuracy at 95% Circular Error of Probability (CEP).

            With newer technology & dual channel receivers, the accuracy is much better. Now, there is Real-Time Kinetic (RTK) surveying, which can give 1 m accuracy at 95% CEP in actual real-time. DGPS nowadays can get better than 5 cm accuracy at 95% CEP sitting at a point for 10-15 min.
      • Three ways to increase accuracy of a GPS:

        1. Averaging.
        Average position data over a long time. Will immensely increase accuracy, because errors (and selective availability) tends to even out over time. However, I believe the precision of the end result is not completely deterministic.

        2. DGPS Get another GPS. Put other GPS in a fixed, known location. Connect to this GPS to your actual positioning GPS, by means of radio, cable, wireless ethernet or similar. Both GPS's should be roughly in the same geographical region, and "see" the same satellites. Any significant positioning error introduced by timing issues (or selective availability) in the GPS system will be the same for both units. Hence, the fixed GPS will calculate a delta, wich will be added by the mobile GPS.

        3. Y-code
        Obtain key for use in military GPS, allowing GPS to decrypt/use y-code to correct the errors introduced in P-code. Increases resolution to 'bout 11m. (Note: this method is, post 2000, not interesting in most areas of the world, since selective availability has been turned off.)

      • Despite these artificial limitation posed by the the US and Australian DoD, apparently everyone who's wanted to has been able to get accuracy to within fifteen meters for quite some time now.
        It's not an "artificial" limitation. When they say GPS has a 36 m accuracy, they mean there is a 95% Circular Error of Probability (CEP) that it will locate your horizontal position on the Earth's surface any day within a 36 m sphere. It's quite possible that the position is more accurate. Some days, the accuracy with a 95% CEP has been as low as 7.8 m, and the 50% CEP as low as 2.9 m (both with only single frequency receivers).

        Do the sattellites give bad readings which can be easily re-set to their true value, is some kind of interpretarion of multiple results possible (a kind of triangulation)? Either way, this has been the case for over five years.
        Before May 1, 2000 "Selective Availibility" introduced a timing error that limited the 95% CEP accuracy to 100 m for civilian receivers. It's been turned off for good now, but the DOD has reserved the right to degrade the signal in a specific region, probably by jamming it.
    • OK. I really hate to be pedantic about this but let's talk.

      1. When you talk about the 100m accuracies, 36m accuracies, 1m accuracies, 5 decimeter accuracies, 1 cm accuracies, etc. in general, you're talking about achievable reproducability with regard to "truth." More on this shortly.
      2. Depending on how you account for the various error terms, the CURRENT system and standard allow for autonomous L1, C/A code-phase accuracies of about 29m.
      3. Since Selective Availability was discontinued, I and others in the "game" have demonstrated routine L1 C/A code-phase autonomous accuracies of 6-10m, with most of the autonomous accuracies leaning toward 6,
      4. The guys who determine error budgets are pessimists (God, I love those guys). They assume that all error terms are scalar additive values. So, they assume that there's no way an error term can be included in the error budget to your advantage. Thus, an error budget that is 6x larger than what I'm seeing regularly.

      With a lot of work, long term observations, and use of a variety of hybrid GPS and conventional surve techniques, as well as using a number of sites with methods of ascertaining their relative positions to precise levels, without using GPS, we have been able to cross-correlate the international network of survey monumentation (more true in the CONUS than some other countries) to GPS positioning. Geodesists use network adjustment statistics (least-squares method) to minimize errors and use stable geometric networks to determine the coordinates in 2D or 3D space of an unknown point of interest. Densification of this network leads to a network that allows land surveyors to use either GPS or conventional monumentation with a degree of confidence.

      When we refer to a 36m error budget, as the DoD spec does, it's a worst case scenario, and is consistent with the current signal specifications. As we enhance the GPS system with additional signals and methods, we should be able to refine the spec to reflect "reality" over time.

      The 100m error budget mentioned refers to a 27-36m error budget for autonomous L1, C/A code phase systems, intentionally degraded using a pseudorandom algorithm called Selective Availability. This was a method of denying precise positioning to a potential enemy of the US. Over time, the integration of techniques, methods and systems to augment GPS autonomous positioning, as well as new techniques (I'm making a few assumptions now) that selective area degradation (denial of quality of service in selected regions/areas) as well as in-theatre jamming led to a US decision to terminate Selective Availability last May. With that, improved C/A positioning was obtained, with an almost instantaneous accuracy of 6m according to hose who were watching and looking for changes.

      In short, the collective errors associated with troposphere (water vapor), ionospheric scintillation (solar influence) and refraction, those associated with signal multipath, Rayleigh propagation, and clock errors associated with both the user-receiver and those vaguaries on the spacecraft themselves... not to mention relativity, conspire to degrade the signal. The pessimists call it 36m. The engineers call it, currently, about 6m in my area (Texas; YMMV if you're close to the poles or near the South Atlantic Anomoly). And for those with some older receivers, you have to measure it and ascertain reality for yourselves.

      There's no way you're going to reliably obtain a 1m autonomous GPS positional accuracy sans augmentation (WAAS, DGPS, etc). If you think you can, let's talk. I want to confirm your procedures and see if it's publishable.

      Can we do better using carrier phase techniques? Sure. I can routinely use 2 receivers (or more, or the US NGS-housed CORS system) and get horizontal accuracies in a least-squares network adjustment on the order of 1cm (2 sigma). But that's not what you were implying.
  • The new performance standard codifies a change announced last year to discontinue DoD's ability to decrease GPS accuracy. See http://www.ostp.gov/html/0053_2.html [ostp.gov]

    This announcement just when the ground war in Afghanistan is starting. Didn't they originally decrease the accuracy specifically for military reasons?

    • Re:GPS accuracy (Score:2, Interesting)

      by vondo (303621)
      Yes, but now they are decreasing the accuracy just in the Afganistan area with what they call Selective Availability.

      Clinton issued the order to discontinue this obfuscation of the signal because of the SA capability and because he realized the benefits to businesses and ordinary people of doing it.

      As a side note, during Desert Storm the GPS system became more accurate because most of the troops had off the shelf GPS units, not the military grade units.
  • by epsalon (518482) <slash@alon.wox.org> on Sunday October 21, 2001 @08:49AM (#2456164) Homepage Journal
    "circumvent ionic interface"...

    In other news, GPS have been announced as circumvention devices under the DMCA, due to the fact that some copyright protection method has been annouced to use ionic iterference...
  • DMCA! DMCA! (Score:3, Funny)

    by TheMidget (512188) on Sunday October 21, 2001 @08:51AM (#2456166)
    and also sets a new baseline for transmission protocols that circumvent ionic interference

    Hey, but won't the ionosphere sue them for DMCA infringment?

  • What kind of crack are they smoking that they want to give up the ability to downgrade non-military sets? Maybe it's just to lull folks into a false sense of security.

    I've never used a civilian set, and now I never want to. How the hell can anyone tolerate 100 meter accuracy? I can do better than that by looking at a map. Now it'll someday get down to 36 meters? Damn, I get pissed off when I can only get it down to 10 meters.

    • What kind of crack are they smoking that they want to give up the ability to downgrade non-military sets?


      Because "non-military" sets are turning up as essential navigation equipment in places like ships and airplanes, where +/- 100 meter accuracy would be a disaster waiting to happen.


      That plus they can now selectively degrade the accuracy in a small region, plus jam it in even smaller regions, means they don't need to worry so much about degrading non-military GPS.

    • You will easily get 10meter horizontal accuracy from an off the shelf unit today. Vertical accuracy is another story. (Seems they try to accumulate the error ito the vertical component, makes sense if your on the ground, sucks if your in the air.)
  • It sounds like this was already done last year, they are just documenting it now. Although it was planned for 2006, the intentional degradation was turned off early. So there really isn't anything new here.
  • by Cerlyn (202990) on Sunday October 21, 2001 @09:08AM (#2456183)

    A civilian differential GPS reciever always was able to do better than what selective availabilty should have allowed. These units gave (and still give) accuracies within 15 meters or so. Given a Loran compensation reciever (used to pick up posititioning signals meant for boats), one can improve on this accuracy by using additional known transmitters located at ground-based reference points.

    If you want "new" GPS units that were recently releaesd in the past year or so, look for units with the Wide Area Augmentation System (WAAS). Implemented alongside with the FAA, these units rely on two additional satilite signals for an average accuracy of three meters.

    Obligatory manufactuers links: Garmin's GPS description page [garmin.com] and Magellan [magellangps.com], another GPS supplier.

    • Cool. Thanks for the info. I was planning to get a Garmin GPS V in a couple weeks and now I'll check these units out again.
    • My Garmin eTrex Vista GPS unit, which uses the new WAAS technology, is accurate enough to know which lane of the road I'm on!

      There's one important thing to note about WAAS, however - It's currently only available in North America. More information about WAAS can be found here [garmin.com].

    • It sounds odd that boaties get better vertical positioning that land-based people.

      I 'spose they need to know that their boat is currently at 0 meters above sea level - otherwise the boaties might get a bit concerned.

      (True story: Standing on seashore looking at handheld GPS receiver - it said I was way up in the air.)

  • by case_igl (103589) on Sunday October 21, 2001 @09:11AM (#2456185) Homepage
    I read over a few of the links but not the full spec. Will this be backwards compatiable or will the current generation of GPS devices just use the old satellite constellation until it dies?

    I can just see it now...All the new GPS applications being developed needing to be tossed.
    Anyone have some details on this?

    Also, as GPS becomes more and more important to the world in general, who is paying the bill? And what price do other countries "pay" if they rely heavily on GPS that is US controlled?

    I don't mind the US being "humanitarian" but it's troubling to think that we will basically be custodians of what could eventually be the primary method of navigation for lots of things.
    Suddenly sanctions against country X means that planes there can't fly, lost puppies can't be found, and GPS tied 911 type services fail.
    • GPS is, in my opinion, one of the coolest things the Dept of Defense has done. Sure, you can criticize them for controlling an important world resource, but keep in mind that they took the initiative to design and build this resource, at the cost of billions of dollars. There's nothing stopping any country from launching its own navigation satellites, but until they come up with that kind of money and sufficient technology, I think it's pretty damn nice of the US to provide the service for free.

      I have a portable GPS receiver (Magellan 315, highly recommended), and I love it. I've never used it for anything really serious, just a bit of mountain hiking. Set a waypoint at your house, and it's impossible to get totally lost. Geocaching (http://www.geocaching.com) is also a lot of fun -- I've found two caches so far.

      As for backwards compatibility, keep in mind that the military would need to upgrade all of its hardware too, which would be pretty expensive. I don't think they'll break backwards compatibility unless they have to. If they suddenly rendered existing GPS receivers obsolete, I suspect there would be a large public outcry, and the DoD really doesn't need bad PR, especially now...

      -John
      • There's nothing stopping any country from launching its own navigation satellites, but until they come up with that kind of money and sufficient technology, I think it's pretty damn nice of the US to provide the service for free.

        I think its very nice too, but the Russians have a comparable system for some years now. Check http://giswww.pok.ibm.com/gps/gpsweb.html#Header_5 0 [ibm.com] for details. I can't find a link now, but some people are considering building receivers that work with both systems so as to improve accuracy/reliability.

        • been done....very spendy, and very accurate I guess.....but I have nothing to back this up, I cant seem to find any links
        • Javad/TopconGPS; Ashtech-Magellan; Trimble Navigation; Leica; Novatel.

          Lots of folks have implemented dual-system receivers that incorporate GLONAS and GPS. Selective Availability was never incorporated into GLONAS. I've done some real-time surveying with GPS-GLONAS dual systems that were impressive in their ability to maintain lock even in areas where there was a lot of physical masking of the sky, because they had so many (14-16, for me) satellites in view at the same time.

          Oh, and for the spatially challenged, GPS does NOT incorporate triangulation, but rather, trilateration.
  • by nizo (81281) on Sunday October 21, 2001 @09:21AM (#2456193) Homepage Journal
    In 2016, as part of the new anti-terror bills flying through congress, every American must have a gps tracking device implanted "for security purposes".
    • In 2016, as part of the new anti-terror bills flying through congress, every American must have a gps tracking device implanted "for security purposes".

      Shouldn't that be every terrorist must hast a gps tracking device implanted.

      These could be delivered to them along with the new backdoored encryption softare

    • In breaking news, Senator Larry Ellison (D Cal), has pushed through a bill requiring all citizens and anyone entering the country to be "tagged" with a security becon.

      In bussiness news Oracle Corporation (Nasdaq: ORCL), stock tripled in price on the board.
      Back to you Taco.
  • I'm about 2 weeks from getting a Garmin GPS V and since it's a plunk down of aboug $450 it would be nice if Garmin's units are upgradeable in this instance. If not then are any other manufacturers? I'll check w/Garmin myself, on Monday, if there's no informative replies and post result as a reply to this thread.

    Tnx

    • According to a previous post, which appeared while I was battling the nefarious Slashdot Form Key error, trying to get my question in. The Garmin GPS V [garmin.com] with WAAS is already cool and won't result in a lost investment, which the article author has backward, the service is getting better, not worse.

      This is what happens when you allow changes into production on a Friday. NEVER change systems on Fridays, except bug fixes. Sheesh, learn some Q/A

  • by europrobe (167359) <daniel&perup,net> on Sunday October 21, 2001 @09:59AM (#2456236) Homepage
    On this side of the ocean, we are working on our very own satellite positioning system, Galileo [galileo-pgm.org], which will be accurate down to 3 meters (last time I looked). It will be all civilian, with several QoS levels - so hikers can get one level of reliability and airplanes another. Unlike GPS, the Galileo consortium will guarantee a certain level of accuracy, which should help in critical areas of operation such as airplane navigation. If there is an accident due to Galileo malfunction, the consortium will accept liability.

    Also, since it's civilian, the military will not have a "Selective Availability" feature.

    • >Also, since it's civilian, the military will not have a "Selective Availability" feature.

      Want to bet? It would not take long before the military would claim "and rightly so" that this kind of ability be added in the interest of national security. If you claim it is sto be so accurate, then why have different levels?
      • Pne has different levels of accuracy in the various positioning systems by using different means int terms of code sequence length and clocking speed to change the error budget. You also achieve a better code- and carrier-phase solution by mitigating atmospheric (ionoshpheric and tropospheric) influences (linear water vapor delay and ionospheric scintillation which manifests as diminished signal strength and non-linear delay) by using both the L1 and L2 signals.

        Selective availability, a long-period dithering algorithm applied to clocks and code-phase signals, doesn't play into this.

        And, from a security and engineering perspective, I'm pretty comfortable with the concept that Selective Availability would not have been discontinued unless another, more geographically agile/specific method of denying accuracies had not been developed. I don't know what it is or might be, and I don't have a need-to-know about it. But I'm pretty confident that we didn't give up a means of denial that doesn't have a larger-scale effect on safety of navigation like SA had.
      • "National security" would actually have to be "international", since this is a joint project involving the whole of EU. There is not one single government who can affect this, there would have to be a majority of countries in Europe.

        Why have different levels? Because they can earn more money this way. First, make the airlines, who can afford it, pay a lot of money for 3 meter accuracy. Then, instead of losing the hiker altogether who can't afford it, they sell a limited service to him and earn more money in the process.
  • Geocaching (Score:3, Insightful)

    by xnn (451788) <nic@mecha.cPERIODo.nz minus punct> on Sunday October 21, 2001 @10:12AM (#2456247) Homepage
    Anybody else use their GPS units for Geocaching [geocaching.com]? (Sort of a treasure hunt using GPS). In practice, the 100 metre figure is a 'guaranteed' level of accuracy, as i have never been anything like that far off. As it is a long weekend here, some friends and I have been using an old Garmin 45 to find all the geocaches within an hours drive of where we live. All caches so far have been within 10 metres of the waypoint, and the three we found today (one in the dark!) were within 3 metres of where the unit said the waypoint was. It is also quite common for match racing yachts to have centimetre accuracy units (often one in the bow _and_ stern), although the expense of these units (~$25000) makes for a very steep price/performance curve.
    • Yes I geocache. Just for fun, I have hidden a cache in a Hide A Key box. I have had more than 20 people find it so far. The location given is close enough they can identify what structure in the park it's hidden in, on, or under. Comments about wanting to tear it apart to find the cache are common. Use keyword "Tiny" if you want to look it up on the website. It is not uncommon for a cache to be found 50 or more feet from the posted location, but many finders post the error seen and other cachers get the same results. Caches on mountain ridges with a good WAAS signal typicaly are found with 10 feet. There is no question which tree, brush, or rock outcropping it's hidden under. Signals in heavy forest on the side of a hill or ravine are more of a job to find.
  • "... transmission protocols that circumvent ionic interference."

    Oh, good, so now it's easier to use GPS on devices with ion engines?

  • Were going to spend billions putting new satalites in orbit, and no one bothered to let the DOD know what the comercial market really needed out of GPS.

    I've done allot of tracking software, for sporting events etc. We've always wanted a GPS system taht would let us put a simple unit on the back of an athlete and just report back his GPS position. Unfortunatly GPS has never been acturate enough to actually use for that.

    But 36 meter's still doesn't solve bigger issues. Like useing it for car navigation systems, or tracking city bound objects (like children, convicts, laptops, cellphones, weapons etc). Im not proposing some orwelian oversight system, but something that would allow us to take GPS and use it as a system for tracking day to day issues. Not quite "Where did I loose my keys?" but "Where did I lose my laptop?" High res systems could also be used for created EXTREAMLY quick and acturate maps, and even building up 3D models of real world enviroments.

    I know high resolution (down to 1 meter or less) is VERRY difficult, but with the kind of money that goes into satalites is it really imposible??

    • Were going to spend billions putting new satalites in orbit, and no one bothered to let the DOD know what the comercial market really needed out of GPS.
      Actually, they solicited a lot of commercial input into the next generation satellites. The original GPS program was DOD only, so they didn't envision many of the uses people have found for GPS. Since last year, the GPS program is jointly managed by DOD & the Dept of Commerce.

      But 36 meter's still doesn't solve bigger issues. Like useing it for car navigation systems, or tracking city bound objects (like children, convicts, laptops, cellphones, weapons etc).
      It's already being used in car nav systems. Many trucking companies, mass transit, police depts, etc. are also using GPS with telemetry tranceivers to track their vehicles on GIS maps. And yes, there are already criminals wearing GPS & tranceivers to ensure they don't violate parole or house arrest orders.
  • My Casio GPS watch (Score:3, Insightful)

    by clemens (188721) on Sunday October 21, 2001 @11:57AM (#2456440) Homepage
    model no. PAT2GP1V [casio.com]'s manual states that along horizontal plane the accuracy is 3.1m average, 10m maximum, and NO ACCURACY DEGRATION under U.S. DOD-imposed Selective Avaliability Program.
    Geez, and they think such an 'upgrade' for GPS is NEWS.
  • GPS Accuracy (Score:2, Interesting)

    by Kymermosst (33885)

    All I can say for the military GPS signal is that it's already pretty damn accurate, and I think the civilian signal is fairly accurate as well.

    When I was in the Army, we had a Magellan GPS receiver, a PLGR (military GPS), and the system our surveyors use for position and azimuth, (not sure if it's classified, so won't say much about it,) and all three of them were giving the same grid location. Of course, the Magellan GPS had to be put in Average mode with a couple minutes of sampling, but it got the same grid location.

    • did a quick google [google.com] search and it came up with this [usgs.gov] page. short version off of that page makes me believe that an azimuth is a cordinate most often used by astronomers in locating things in the night's sky. this report talks about accuracy when using the azimuth for taking down telemetry and it's accuracy, ect. kinda interesting.
      • An azimuth is merely a direction or bearing. For 2D navigation, an azimuth is simply the same as degrees on a compass (if your compass reads in degrees), as in, the azimuth to the north pole is 0 degrees. (or 0 mils if you are in the artillery)

        For 3D navigation you have to give two 2D azimuths to point in one 3D direction... if you have a 0;0 reference point... say you measure it in degrees, than you can reference any direction with two 2D azimuths in degrees. (Like Star Trek... bearing 245 mark 16)

        Hard to describe. I'm sure someone could explain this a lot better.

  • One of the facts being overlooked is that any thing designed for "military" application is usually done by the lowest bidder.

    As a former military person (USN, if ya'll care) this was evident in many pieces of equipment I had to deal with in the service.
    Don't get me wrong, the equipment was functional, as it should be, but sometimes a lot of stuff was meant to be "sailor proof"...one step beyond "idiot proof", because any devices 'intended' use will invariably be expanded unintended uses.

    So if you take into account the specs of any equipment, there is always a tolerance for these devices...not only the physical abuse of changing hands many times, transporting, shipping, and varied levels of (in)competancy.

    You have to realize that for better or worse, that the armed forces (I have to laugh, this is me to a 'T') personel are both the best and worst case scenarios.

    Now that I am on the periphery of GIS (admin for a GIS training lab...man what a lot of data just for one state) I've gotten to play with the "toys" and for those out in the field, 30 to 100 meters ain't that big a deal, it is acceptable.

    You would think it would not be, but consider:
    A satellite has already imaged the area, and sometimes it has been surveyed from the ground and always surveyed from a aircraft plus the final check is to drive/walk the surveyed area with a GPS unit to do a final "triple check".

    It seems more or less an integrity check.
    Even the GPS is subjected to a test or two, where a building, area, large parking lot is measured with GPS points assigned and then checked against previous data.

    It must be within an acceptable range (in civilian use, mind you) because I have not heard any complaints. The device was actually kind of neat (was the usual "military yellow" gear color) and had a palm pilot like interface, 6 tabs on the display, about 8 buttons to navigate and mark and save/recall points.

    In the end, if it is 3meters, 30'ish meters or 100, I hate to sound cliche, but close enough for government work, perchance?

    I don't know, but as long as the device does not say I'm in the artic circle when standing in the AZ desert, its gotta be doing something right.

  • by Anonymous Coward
    this is nothing new at all. You're being a bit vague when you say it's a "new standard." Think of it more like a report on the current state of GPS for civil users; the DoD is simply saying that their old estimates of average performance were off and they're correcting themselves. The numbers in that report only reflect what can be done right now with GPS (in terms of a stand-alone receiver, no differential GPS).

    The next real improvement in GPS accuracy will come with the launching of the next few blocks of satellites (IIR, IIF, III). The Block III satellites aren't slated to be deployed until at least 2010 [gpsworld.com] and will include the new M code for more accuracy. Even sooner, the Block IIF satellites will support the new L5 channel for civil users which will give the public sector a big improvement in their accuracy. The C/A code (for public users) will be turned on L2 in the release of the IIR satellites starting in a couple of years. Up to now, the L2 channel was only for P(Y) code which public GPS users didn't have access to (P(Y) is the military PPS code (precise positioning service) and is heavily encrypted). And more improvements will be made as the OCS (operational control segment - the Air Force group that monitors and controls the GPS constellation) that will make GPS even more accurate and reliable.

    But don't expect any more significant improvements in GPS accuracy until these new blocks of satellites are launched. Of course, these improvements exclude things like WAAS and other differential GPS solutions which will give a much more precise position solution than any single receiver can accomplish.

    Here's a good page [navy.mil] describing some basic GPS terms I used. Also, for a good summary of the lastest GPS modernization efforts, read this article [gpsworld.com].

    t.
  • The clock signal for civilian use is less precise than the military one and 'selective availability' degraded it in a kind of random but non-gaussian manner. Early on clever folks found that they could increase the accuracy in spite of that by placing a second receiver in a known location and either post processing the data or broadcasting the signal from the fixed location. This Differential GPS could have sub-cm accuracy. Other clever folks used other aspects of the signal such as phase difference to boost the accuracy. Others made receivers that could use the Russian and US GPS at the same time. In other words Selective Availability was cracked about 10 years ago but the Military refused to kill it. I think that it was for political reasons - not wanting to hear that a rogue missile directed against us used our own GPS for navigation , for instance. It is possible to mount antennae on the wingtips, nose, and tail of an aircraft and use differential GPS to determine the attitude to a 1/100th of a degree or less. This can be combined with new, cheap, Inertial Navigation systems that allow you to point an IR camera from an aircraft and drape the image over a digital terrain model or map in real time. I think that the Garmin site, http://www.garmin.com, claims less than a meter horizontal accuracy with WAAS for the Garmin V. Nate
    • Did anyone check this [wsrcc.com] out? They deliver GPS data for a fixed point in the Bay Area to do DGPS. Wouldn't it be cool to setup a network of these stations/sites all over the world so you could select the one closest to your current location?
    • Actually, it wasn't killed sooner because several companies had sprung up, selling DGPS (differential GPS) services that got around SA and gave more accurate results. Said companies lobbied congress to continue SA because turning it off would basically remove their reason for existing.

      For the record, industrial-quality GPS ($1,500-$5,000) is accurate to about a meter, with maybe 3m of drift over time. I work in the precision agriculture industry, and one thing that we do is map yield performance based on GPS data. Handheld units are less accurate only because the antennas on the units are smaller.

      --
      Dave
  • I heard something in the last year that talked of a planned European GPS. Does anybody know anything about it? I think it was supposed to be deployed before the new US one, and offer more features then the current US one. I wonder if it renders the built-in inaccuracy of the US one a moot point?
  • The new GPS network will also incorporate Digital Rights Management Technology by Microsoft(tm) to insure people don't get too used to free positioning. So, remember folks: when you go down to the woods today, be sure to bring your credit card, else your be lost forever...

    Now availible!!! the new MS GPS-MP3 player!! yes, now you can listen to your favourite tracks _and_ know your position to within 1m (20000m for un-registered users). But remember, don't try to break our DRM system, or go faster than 80mph: 'cause now we really do know where you live.

    (Microsoft(tm) GPS network(r) may not be accurate and should not be used for mission critical applications, in the event of network outage, Microsoft is not responsible for loss off life or ruined terrorist plans, See Mictosoft GPS-NT)
  • I'm kinda surprised that the DoD would go on with their decision to make civilian GPS as accurate as it is technologically possible, even after we know that the hijackers located and flew into their targets on September 11th using civilian GPS. I'm not saying that the hijackers should spoil the treat for the rest of us. I just find it paradoxical.

    And what if other countries design their offensive weapons to aim with our system? (Temporarily shutting civilian GPS down might work.. then again, we can tweak the numbers that are transmitted to any civilian client during this event so that we are able to redirect those weapons to our targets)

    • I'm kinda surprised that the DoD would go on with their decision to make civilian GPS as accurate as it is technologically possible, even after we know that the hijackers located and flew into their targets on September 11th using civilian GPS. I'm not saying that the hijackers should spoil the treat for the rest of us. I just find it paradoxical.



      Why? It's a navigation system. Of course it's going to be installed on commercial airliners.



      Remember the line from "Hunt for Red October?" (The movie, not the book): "With a map and a stopwatch I can fly the Alps in a plane with no windows." It's not much more complicated. Without precise satellite equipment, the hijackers would be forced to navigate with a chart and a compass and an airspeed indicator and a clock. That buys an extra minute or ninety seconds of life in the target building. Not much help at all.



      Shutting down GPS will really hurt civil aviation, but with no benefit. Better to just keep the terrs off the flight deck.

  • Of course, NASA released Blackjack [nasa.gov] a while ago.
    And they wouldn't post my story about rotten.com being banned in Germany.
  • by Anonymous Coward
    For those who work in the GPS community the DoD statement has a faulty reference. It links to ICD-GPS-200 revision B when in fact the last release of the ICD was revision C. Hopefully this will be corrected shortly.

    For those who are wondering why the DoD removed the "degredation" from the civilian GPS signal it is because they now have a more effective means of preventing enemies of the US from using GPS - selective deniability. This link [wired.com] talks of its use in Afghanistan. By improving the signal to friendly nations it improves GPS as a product which means that US companies who make GPS equipment (and dominate the market) can improve their sales figures.

    scott.

  • GPS has not only an accuracy of 1m of military uses but a resolution of a few inches. this is accomplished by feeding the satellite input into a special device that is used for missiles to strike accurately hardened targets

"But this one goes to eleven." -- Nigel Tufnel

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