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Is National Differential GPS Lost?

Posted by ryuzaki0 on from the so-where-are-we-again? dept.

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."

6 of 109 comments (clear)

  1. Doom and gllom for punchcards! by EmbeddedJanitor · · Score: 5, Informative
    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....

    --
    Engineering is the art of compromise.
    1. Re:Doom and gllom for punchcards! by Chanc_Gorkon · · Score: 3, Informative

      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.

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      Gorkman

  2. Re:Why don't they just publish the P(Y) keys? by LWATCDR · · Score: 3, Informative

    No.
    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.

    --
    See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
  3. Re:Why don't they just publish the P(Y) keys? by monopole · · Score: 3, Informative

    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.

  4. used by hundreds! by frovingslosh · · Score: 4, Informative
    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.

    --
    I'm an American. I love this country and the freedoms that we used to have.
  5. Re:You Know, This Kind of Is a Problem ... by Anonymous Coward · · Score: 3, Informative

    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 folks working there will be affected in any significant way.