Is National Differential GPS Lost?

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."

Comments

Of Course!

[duerra]

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.

Doom and gllom for punchcards!

[EmbeddedJanitor]

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....

Re:Doom and gllom for punchcards!

[Chanc_Gorkon]

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.

Article Unclear

[uab21]

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?

WAAS & CORS = better?

[Jurisenpai]

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.

Re:Why don't they just publish the P(Y) keys?

[LWATCDR]

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.

LOST

[EddieBurkett]

If NDGPS is indeed lost, can't we just use its GPS to find it?

You Know, This Kind of Is a Problem ...

[eldavojohn]

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:You Know, This Kind of Is a Problem ...

[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 folks working there will be affected in any significant way.

Budget Cuts

[dch24]

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.

Re:Why don't they just publish the P(Y) keys?

[monopole]

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.

used by hundreds!

[frovingslosh]

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.