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Is National Differential GPS Lost? 109

Nealix writes, "This article at GPSWorld reports that National Differential GPS (NDGPS) is endangered in the 2007 budget. This has ramifications for a variety of government programs such as the Intelligent Transportation System and Positive Train Control by the Department of Transportation. Blind people and robots also benefit from highly accurate GPS navigational capability provided by NDGPS, which appears to work better in the urban canyons. If NDGPS loses, the winner would appear to be the FAA-backed Wide Area Augmentation Service (WAAS). Of course, what would be really cool is to see more GPS sites around the country make DGPS data (RTCM) available over the Internet."
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Is National Differential GPS Lost?

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  • Of Course! (Score:5, Funny)

    by duerra ( 684053 ) on Tuesday September 05, 2006 @03:11PM (#16046737) Homepage
    Ah yes, of course GPS making use of DGPS data (RTCM) would be better than FAA-backed WAAS if NDGPS loses - everybody knows that. Now, BRB while I RTFA.
    • STFU

    • What will this mean for us street atlas GPS Users?
      • nothing
      • by mikael ( 484 )
        Nothing for you to see here, please move along ....
      • Re: (Score:3, Informative)

        by jfengel ( 409917 )
        Your street atlas GPS probably doesn't use NDGPS. It uses plain old satellite-based GPS, and that's just fine.

        Differential GPS greatly improves your precision, from meters to centimeters, but you don't really need that to give directions. You'd want it if you were actually letting the thing steer your car, but we're not there yet.
        • Re: (Score:3, Informative)

          by Goldenhawk ( 242867 )
          >Your street atlas GPS probably doesn't use NDGPS. It uses plain old satellite-based GPS, and that's just fine.


          Actually most consumer devices ALSO uses WAAS. Plain old satellite is "just fine" even without WAAS, but WAAS really helps refine the position.

          Especially in the "urban canyons", normal GPS signals are pretty bad at times. Get in the city around tall buildings, and you'll see your accuracy get into the hundreds of feet if only three satellites are in view and lots of signal reflection
          • Re: (Score:3, Interesting)

            by skroz ( 7870 )

            Sure, out in the middle of a cornfield in Kansas, you might not care about DGPS, but in that case you often have eight or ten satellites available and an accuracy of perhaps 15 feet. Not in the middle of the city.

            Not true. In the middl of a cornfield in Knasas, where farm machinery is uften automated and steered via GPS, extreme precision is critical. Non only that, but your sample rate is often much higher than the .5 to 1 Hz seen in most consumer GPS units.

            If your thresher (or whatever) is out in the fi

            • Wow, I never knew they had that level of automation.

              By the way, do you know how the farmers still stay in business? I heard from a relative they only get about $10/acre at best. That just doesn't seem nearly enough to provide for the family, let alone buy GPS steering. Or do they also get the subsidies then?
              • by topham ( 32406 )

                Doing a search on the Internet reveals crop guarantees at $167/acre when I did a search on Wheat. Now, I didn't very which year, etc. But I expect the document is 'current' (last five years or so).

                $167/acre, with 1000 is $167,000 - costs = ?

                While I don't know what farmers costs are, I saw numbers published a few years ago where the local farmers were complaining because they only made $45-55,000 Net Income.

                I don't know about you, but where I live thats significantly above average net income.

                You may not get
                • by shaneh0 ( 624603 )
                  This is true. The trouble happens because a family farm has finances that look more like a Family and less like a Business. For example, the fancy GPS equipment that was written about previously was probably purchased on credit, and this stuff is very expensive. A modern farm wouldn't blink their eye at 1/2 million dollars in equipment.

                  So as long as everything goes smooth, a farm can keep the cash flow necessary to pay their loan payments, purchase their seed for the next season, and pay their salaries. But
        • Differential GPS greatly improves your precision, from meters to centimeters

          This is incorrect - DGPS improves the precision from somewhere around 15 metres to 3 - 5 metres - certainly nowhere near centimetres (which is pretty much impossible with GPS due to the wavelengths involved - I understand Gallileo will be providing a high precision service though).

          But I'm unclear on why the loss of funding for DGPS is big news - is anyone still using DGPS? If so, why? If you've got a view of the equatorial horizon
    • by eldavojohn ( 898314 ) * <(eldavojohn) (at) (> on Tuesday September 05, 2006 @03:36PM (#16046906) Journal
      You jest about this, but I think this is a problem.
      The problem facing NDGPS today, in my opinion, is the lack of a 'killer app.' In other words it's a neat tool and serves hundreds (if not thousands) of people on a daily basis, but if it disappeared tomorrow, life would go on. Therefore, when it comes to cutting the budget during tight times, programs like NDGPS are prime targets.
      I disagree. The fact that you demand it have a "killer app" instead of clean functionality tells me that you lack sound judgement on this service. It's a service for locating yourself. We put green & blue information plaques by the sides of roads that tell you where you are. They're called 'road signs.' It probably costs more than $10 million a year to maintain them. I, for one, would like a public service that keeps me informed as to where I am.

      Now you're telling me that we can't afford to clip another $10 million off the Defense budget [] and give it to this service (which may, arguably, help the coast guard in defending our shores)? Come on, we spend way more on military than any other country. It's good to maintain military superiority but do we really need it when you look at that chart? The next highest is China with maybe an 1/8th as much spending as we do. Give me a break!

      There's no way anyone can justify cutting the spending on this program given what we've invested in it and how useful it is. When you look at where the rest of our spending goes, $10 million is nothing. No one can complain that the cost versus potential utility of this thing isn't high enough.
      • Re: (Score:3, Informative)

        by Anonymous Coward

        Now you're telling me that we can't afford to clip another $10 million off the Defense budget and give it to this service (which may, arguably, help the coast guard in defending our shores)?

        This kind of DGPS (type-1 or type-9 messages only) that the Coast Guard sends is of very limited utility. Now that "Selective Availability" (intentional noise added to the civilian GPS signals) is gone, there is very little positional improvement one gets from their DGPS. If they kill it, I doubt anyone but the folk

      • Re: (Score:3, Interesting)

        by ronanbear ( 924575 )
        If it's only $10m then maybe the companies that sell GPS systems would pay for it themselves if they care that much about it. It's fair that companies wouldn't be able to fund GPS in its entirety but customers that want extra accuracy should be willing to pay for it.

        SA wasn't a big deal to yachtmen as it was accurate enough. It was a much bigger deal for car navigation systems (think parallel roads 50 yards apart and chaos at junctions).

        A few days after SA was turned off I went for a walk and the track

    • by punkish ( 989278 )
      I think I will shutdown my GPS, go home in my BMW, and watch CBS on my VCR.
    • To be completely honest... I laughed until I cried after reading your post.

      That was great man!
  • by ronanbear ( 924575 ) on Tuesday September 05, 2006 @03:19PM (#16046790)
    Would not actually be hard. Technically you could do it yourself. Really at it takes is a fixed location GPS (calibrated) hooked up to a server which processes the NMEA data and uploads the correction dynamically.
    • by EmbeddedJanitor ( 597831 ) on Tuesday September 05, 2006 @03:25PM (#16046829)
      Everything has its natural life, and WAAS is now a good replacement for beacon. So what if beacon differential goes away? WAAS is better: it is easier to add to a system (it uses L1 and typically needs no extra hardware vs beacon needs a special receiver etc), is cheaper, and is easier for customers to use.

      I didn't mind punch cards being phased out either....

      • by Chanc_Gorkon ( 94133 ) <> on Tuesday September 05, 2006 @04:31PM (#16047334)
        This post hits the nail on the head. Only thing I would add is SA has been turned off for quite some time now and WAAS is in even the cheapest GPS receivers now. DGPS also ONLY worked if you were in range of a body of water too (Coast Guard sites if I remember correctly). PLUS newer GPS receivers can hold a lock on more satellites then the first model GPS receivers were capable of. At this point, I could care less about DGPS. I have not seen a receiver that has supported this in many years with the only exception being Marine GPS receivers. DGPS needs to go just like LORAN did many years ago.
    • by puhuri ( 701880 )

      In theory yes, but you won't get the needed information from a normal GPS receiver. To calculate DGPS correction, you must calculate error for each satellite and feed that to other GPS receiver. If you just take difference between the right location and the location you got from NMEA output and use that to correct postition indicated by other, you will get greater error than without.

      This is because each receiver picks a different set of satellites.

      • Budget Cuts (Score:4, Insightful)

        by dch24 ( 904899 ) on Tuesday September 05, 2006 @03:38PM (#16046916) Journal
        DGPS does the correction on a satellite-by-satellite basis. The GPS receiver must support DGPS corrections, which are uploaded to the receiver to include in its internal calculations before the separate satellites are combined to form the final result.

        Remember when GPS itself was thought to be in danger back in 2000 []? Remember when there was talk of balancing the budget? Read this article [] all the way from 1996 about the military importance of GPS technology. It's worth the read.

        About the NDGPS vs. WAAS debate: I work for a group that relies heavily on GPS for aviation purposes. As the number of uses for GPS expand, as they inevitably will, new technologies will spring up. NDGPS vs. WAAS is like 802.11g vs 802.11a. I think they both have a place. If the government won't support NDGPS, perhaps there is a commercial application? What are the FCC regulations on the 300KHz spectrum? If no one will pay for it, let it die, I think.

        Okay, <rant>
        I laughed when I read, "Therefore, when it comes to cutting the budget during tight times, programs like NDGPS are prime targets." How are we cutting costs when we just ran up a record high deficit in the last two years []? I like it that we're cutting costs. Let's cut some of the really big ones, like military spending!
        </rant> Couldn't resist.
        • by danno ( 7334 )
          I like it that we're cutting costs. Let's cut some of the really big ones, like military spending!

          Except remember, GPS came from a black budget military spending project that made the military budget look bloated. Look before you bite the hand that feed, and make sure it's not going to slap you after you bite it.
    • Re: (Score:3, Informative)

      Hmmm.... google for 'dgps internet'... and guess what you find: DGPS corrections over the Internet []
      • OP was asking for *more* sites. Those corrections are only valid in a range of a few tens of Km around the site where they originate from.

        But, as someone else said, WAAS is much simpler to implement so I don't really have much of a problem with this - altough one could arguee that the two systems complement each other, which I'm not sure is the case, but ...
  • by Anonymous Coward
    As an outsider, I see two technologies that do more or less the same thing. One is better in every way. Its only downside that it's not usable in certain situations where the other might possibly be used.

    And this is a reason to spend a couple hundred million plus $10 mil/year in operating expenses?

    I know it's not a large amount of money compared to the national budget, but it's still a lot of money.
    • by Isaac-1 ( 233099 )
      The difference is WAAS depends on a clear view to a satelite in geosync, all fine and good for the FAA that developed it for aircraft use where the GPS antenna can be on the top of a plane, not so good when you have mounted your antenna on a ship or a truck where either other parts of the vehicle or the terrain might block the signal.
      • And for some specific data on why this is bad, consider that WAAS depends on line of sight view to the satellite. In Portland Oregon, hardly the end of the earth, that line of sight is 7 degrees above the horizon when I last checked. If you are behind even a modest hill, the signal is unavailable. WAAS works great for planes, but is less than perfect by far for ground based use. In cities, it's basically unusable. You can get the stats from []
        • GPS satellites are not geostationary. At any point in time there should be 5 satellites within range/LOS, regardless of where you live.
  • Wouldn't the "Precise" code give better resolution than either DGPS or WAAS?
    • by LWATCDR ( 28044 ) on Tuesday September 05, 2006 @03:32PM (#16046872) Homepage Journal
      DGPS can be far more precise than military precise setting. A resolution of one meter is more than good enough for any weapon system that would use GPS.
      I remember hearing about a form of DGPS that has a lot higher resolution than one meter. It is often used for surveying.
      • by monopole ( 44023 ) on Tuesday September 05, 2006 @03:40PM (#16046930)
        Precisely, Carrier Differential GPS can be on the order of less than 10 centimeters on a good day. The other factor is that CDGPS works off of precision epemeredies that are released the next day. Good for survey, not handy for weapons. (There is real time kinematic GPS with such precision but not much in the civilian world.)

        That being said P code recievers make differential and carrier differential easier.
        • by LWATCDR ( 28044 )
          I probably should have left out the part about weapons not needing more than ~1 meter resolution. Any way thank you for the information on CDGPS.
        • In my ham radio club we have a guy who used to run the Astronautical Measurement section. He gave a talk about GPS and DGPS one night, and finished by talking about CDGPS. Basically, it's so good you could fly a plane by placing receivers at the nose, tail and wingtips. It could tell you what the attitude of the plane was to a good enough extent that you could fly it remotely based just on the information from those four receivers (well, you'd need a control system too, but you know what I mean....) I f
          • Doh! Sorry, that should be "a guy who used to run NASA's Astronautical Measurement section". His group was the one that had to measure how close Mars was when it was at its closest point, stuff like that.
      • We use Leica DGPS equipment with our own DGPS base station. Accuracy depends on how far you are from the base station, but on our fairly small island we reckon on 1-2 cm accuracy, horizontally and vertically.
        This does depend on having sufficient satellites in view - this is a problem under trees and close to buildings and steep slopes.
  • Article Unclear (Score:5, Insightful)

    by uab21 ( 951482 ) on Tuesday September 05, 2006 @03:27PM (#16046848)
    Obviously I have missed something in TFA. It states that there are areas where NDGPD is available that WAAS is not, but that also WAAS is available where NDGPS is not. NDGPS requires additional hardware which is A) expensive, and B) bulky, whereas WAAS is available on pretty much all currently available receivers. Both systems (NDGPS and WAAS) have comparable accuracy (~1 meter).

    Why, again, should we be sorry that NDGPS is going away? It sounds like market forces at work here. The only specific instance that TFA mentions where NDGPS has an advantage is *some* in-building penetration. Why should we build out a *national* network for only some in-building penetration? It sounds to me that WAAS is getting funding because it is technically and economically the better solution. Why is this a problem?

    • Re: (Score:1, Funny)

      by Anonymous Coward
      Why is this a problem?

      Obviously it was written by a NDGPS hardware provider who is watching their future go awry. Won't anyone think of the corporations?!
    • Re: (Score:2, Interesting)

      by Isaac-1 ( 233099 )
      WAAS requires that geosync be visible from the GPS receiver there are many instances where this can be a problem, for one thing it generaly means the GPS antenna be mounted at the highest point on the vehicle (a potential problem with ships as by law lights must be mounted at their highest point) also terain and even trees, may be an issue for trucks, etc particularly in more northern states where geosync appears low on the horizon.
      • Being northerly makes it harder to see a geosync satellite. What's less obvious is that being too far east or west creates the same problem.

        Look at it this way: whether you go up/down or right/left, you're still moving away from the point where the satellite is overhead.
        • What's less obvious is that being too far east or west creates the same problem.

          Not really - there are several SBAS satellites at different longitudes with overlapping footprints. If you can't see one then you are likely too far from the equator or so far out to east/west that you wouldn't get any useful DGPS data anyway.
  • by Jurisenpai ( 261790 ) on Tuesday September 05, 2006 @03:32PM (#16046869) Homepage
    I personally *hate* using the NDGPS (beacon) real-time corrections. We only have two reference stations in my state and neither are worth a damn in my city. I work as for a major GPS company, and though we do sell beacon receivers quite briskly, I hate using them.

    I much prefer using WAAS for real-time, especially after the two new satellites are up and fully functional. I do post-process most of my data, however, so the CORS stations work just fine for my needs.
  • LOST (Score:5, Funny)

    by EddieBurkett ( 614927 ) on Tuesday September 05, 2006 @03:35PM (#16046892)
    If NDGPS is indeed lost, can't we just use its GPS to find it?
  • by NoRefill ( 92509 )
    WAAS is the next step in this technology. Let the dinosaur die and let's move on.
  • Think about the implications if WAAS (and soon-to-arrive LAAS) is decommissioned -- the FAA has already issued WAAS-based LPV approach plates for IFR ops. Switching to another system would cause a huge momentum change in a critical sector of the safe operation of our airways.

    The FAA upset thousands of pilots when they pulled the plug on TIS (Traffic Information Service) when approach radars (ASR 9 to ASR11) were upgraded and their investment in TIS equipment was obviated -- the one they chose, ADS-B (Autom
    • by GnuPooh ( 696143 )
      LAAS was zero'd out in the FAA budget two years ago and is still zero. So it's unlikely LAAS will happen any time soon if at all.
  • Blind people and robots also benefit from highly accurate GPS navigational capability provided by NDGPS

    Of course, nobody cares about poor blind robots, running around, bumping into walls. And what about blind human/robot hybrids? Are they stuck with their bionic seeing eye dogs?
  • I understand the Positive Train Control part; you need to be able to tell where a train is in order to tell it what to do. I'm having a little more trouble with the Intelligent Transportation Systems part.

    You don't necessarily need GPS to tell automobile drivers what's going on ahead of them; there are other, infrared or magnetic loop current-based ways to do that already.

    • by lohphat ( 521572 )
      > I understand the Positive Train Control part; you need to be able to tell where a train is in order to tell it what to do. San Francisco Muni drivers could use all they help they can get. Just about got killed this morning when the train did two emergency stops sending people flying. This all heppend after the driver finally turned off his right turn signal after being in the tunnel for 5 minutes (they're surface trams and underground part of their routes). "Sorry, uh... computer glitch...." My a*
  • Wont someone please think of the robots!
  • used by hundreds! (Score:5, Informative)

    by frovingslosh ( 582462 ) on Tuesday September 05, 2006 @03:57PM (#16047046)
    Right from the article: "used by hundreds if not thousands of users on a daily basis". This pretty much sums it up, there is an old technology that needs a special extra receiver that is used by hundreds of people (or maybe more) and costing millions of tax dollars, while there is now a widely deployed WAAS system that uses the same satellite receiver as GPS (no extra receiver required), is used by vastly more people, covers the country, and somehow the politicans have caught on that the old system is a waste. Although we may not be able to stop paying billions for bridges in Alaska that go to islands with 50 people and will admittedly help only realestate investors, at least they see the folly in supporting this old system. It should be shut down, in spite of any private agenda the original poster has.

    On top of this, WAAS isn't the end of the line, there are more systems coming on-line that will improve GPS acuracy even more. The old system was OK for what it was, but the need for extra receivers by each user certainly limited it's adoption. It should be phased out.

    And one thing I just have to comment on from the article and even the /. blurb: "Positive Train Control"! Are we really to believe we need taxpayer funded meter accuracy for GPS for train control? Do these trains really wander from from the tracks we know the location of? Isn't normal GPS accuracy just fine for choo-choo trains? And in the rare cases where higher accuracy might come in handy (although should hardly be needed), such as a switchyard, couldn't the location itself provide a small simple system for far less cost than asking the taxpayers to support it for this special use? You don't even need Internet data for this, you just have to agree on the location of the stationary differential receiver site and put a receiver without WASS there, it's error from it's known location is the same or better correction information than you could get from the Internet.

    • Re: (Score:3, Funny)

      by bunions ( 970377 )
      > Do these trains really wander from from the tracks we know the location of?

      well, duh: Amtrak. helloooo! Anybody home, McFly??
  • FTA:

    The e-card provided information about the owner's current context and activities.

    In other words, "managers could track employee's activities without having to look over their shoulders."

    Ummm...could I skip this 'upgrade'?
  • by viking2000 ( 954894 ) on Tuesday September 05, 2006 @04:12PM (#16047152)
    There is no need for NDGPS. How WAAS works

    Just to explain to the submitter if this is not already crystal clear: There is no need for NDGPS. WAAS has fortunaltely replaced it.

    NDGPS required a seperate receiver to get the error signal from a ground based transmitter. You also had to be near a ground based error transmitter for this to work.

    The ground based error transmitters are still there, and more are beeing added. Instead of transmitting locally, a database of errors over a wide area is constructed, and a geostationary sattelite transmits the error database on the same wavelenght as the other GPS sattelites to all GPS devices. All that is needed for this is typically a firmware update in the GPS unit.

    Simple, effective, cheap.
  • by JustNiz ( 692889 ) on Tuesday September 05, 2006 @04:36PM (#16047376)
    Because thats what my Garmin GPS uses. It (and I) have never heard of NDGPS so I hope WAAS doesn't get phased out. given that it also makes sennse to have a single standard, it makes sense to me for NDGPS to go away.
  • WAAS is better. All you need is one GPS reciever and it costs noting and is available everywhere GPS is. Differential was a great idea but they used a second back channel radio to broadcast the data. WAAS is almost the same thing but uses the GPS system itself to broadcast the data. Smarter really.
  • At first glance I thought NDGPS was some synonymic acronym
    for WAAS and it sounded disturbing. On a slightly closer
    reading I see that WAAS is not in danger. It never was
    and won't be. Hundreds if not Thousands of 'connected'
    yacht owners would never find their moorings if WAAS was
    shut down. Some of these are the source of government, er,
    oil. I'm sure no one in government would want to loose
    these users of WAAS.

  • Three items of note:

    1. Sky visibility can significantly degrade your accuracy via WAAS. Personally, working in a lot of areas with random overhead cover (trees) I prefer NDGPS to WAAS even if I have to download the corrections and post correct. In a test I ran in a suburban forested park NDGPS was able to meet the 1 Meter accuracy claims even with heavy overhead (40+ foot trees)in a comparison vs 6inch pixel aerial photography. WAAS consistantly got a ~2-5 meter error on the same locations.

    2. NDGPS station
  • My cell phone supports AGPS, while I don't know the specifics about the implementation (Motorola RAZR v3c) I wish I could take advantage of the fact it can do it.

    Instead the phone company makes it impossible to do anything with it. In my case they don't even offer services for it.

    somedays I'd like the technology to serve me; instead of big brother...

  • Ya know, when I found this out I had to forward it onto our business group. Funny thing is, they had no CLUE it was happening.... and they aren't worried because the next product won't need it.

    Of course, when you're talking sub-meter accuracy... well, here's hoping I have better employment by then since they're unwilling to listen...
  • I always wondered if an individual could setup their own DGPS and use it for navigating home robots. For example, my Roomba [] would be more efficient if it had a layout of my home and knew where it was. But GPS is too broad. But could I place a DGPS receiver in my house and make a GPS accurate to 10 cm (As I've heard people claim is possible)? If I understand the principle correctly, DGPS is just about knowing your position precisely and sending out correction information.

    How common are DGPS receivers?
  • Well, there would still be Canada's national DGPS service, which covers most of the northern US (plus Alaska)! Plus the expensive commercial services if you really needed it.


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