GPS 'Selective Availability' Ends — Where Are We Now?

from the map?--we-don't-need-no-stinking-maps dept

The US GPS system set its ‘Selective Availability’ levels to zero back in May 2000, and now the DoD is permanently removing the feature that allows the US to degrade GPS signal accuracy at will. While this probably saves US taxpayers a few pennies by not having to include some unnecessary signal processing parts in new GPS satellites, the decision also seems to mark a turning point in the availability of wireless location data. With more and more location based services cropping up that don’t actually rely on GPS signals, such as the location-aware mobile search from Sprint and Microsoft which triangulates a caller’s position between cell towers, the access to accurate location data is becoming commonplace. In fact, as more terrestrial wireless signals broadcast potentially-useful location data everywhere, the idea of using far away satellites to tell us where we are seems like an archaic concept — and projects like Galileo begin to sound even more redundant. The adoption of GPS (or location-aware) devices reduces the uncertainty in several aspects of our lives — giving users the sense that they can’t get lost. So interestingly, the DoD’s decision to switch from possibly hiding location information in order to keep Americans safer — now to accepting that accurate position data is a critical component of our economy’s future efficiency — indicates a tacit admission that the open accessibility of information really does make us more secure.

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Companies: microsoft, sprint

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Comments on “GPS 'Selective Availability' Ends — Where Are We Now?”

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Anonymous Coward says:


…the DoD is permanently removing the feature that allows the US to degrade GPS signal accuracy at will.

First off, remember that the DoD considers lying for the sake of national security to be part of its job. Now, all the DoD is even claiming is that the new satellites won’t have “selective availability”. That could just mean that they’re calling it something else on the new satellites. Same thing, new name. What do you want to bet that military navigation equipment will continue to have the ability to override supposedly non-existent SA anyway? The US has been fighting hard against the European Galileo system with claims like this designed to reduce support for competing systems. This article is an example of how effective such claims can be. Hook, line and sinker.

RandomThoughts (user link) says:

I doubt the intent was showing how information can make us more secure. It has been open for quite a while, now they are just ordering them without the ability to take them out in some case.

Not having the ability to shut down access when needed would be stupid unless it was determined that other means could be used, so what’s the point?

Authorities can shut down cell communications, phone communications and pretty much any other type of communication, why wouldn’t we want them to have the ability to control what is known when needed?

Michael Long says:

More Propaganda.

I think the Propaganda post above is dead on. Do you honestly think this countries leaders and military would give up that kind of control?

Further, it may be the party line that such information is critical… right up until the point where someone flies a GPS-guided model plane packed with C4 into some high-profile target.

Now, if American BUSINESSES say that such information is critical in providing pin-point advertising to consumers, then all bets are off…

InTheKnow says:

The beauty of misinformation.

The understanding of selective availability seems flawed. The gov opened it up to the commercial sector so that it could be used by others. It was mandated that civilian recievers be accurate up to a point. Not that they wouldn’t turn it off.

Defense GPS recievers operate in a similair fashion to civilian units but have no limitations that are introduced to civilian units. Simply put they are much more accurate.

First and foremost GPS is and always has been a military project. Outside options like gallileo degrade the effectiveness of GPS as a defense tool. Thats why its being fought. The russian system itself has the same effect. However they are both rendered moot basically because of the lack of ability or funding to launch their own constellation of sattelites. Setting up a GPS constellation is no trifling matter (multiple planes of rotation times multiple satellites per plane and by the time you factor in spares in case of malfunction its no not a trvial thing to consider costs).

Military GPS is a powerful tool tactically. Location based services like navigation by triangulation of cell towers is fine for the civilian world, but as a tool it tactically has its limitations.

By removing SA all it says is they are no longer going to limit reciever accurateness but don’t for a minute think they are going to give up their edge. COntrol of the GPS system will continue to be in the hands of our military. As well as the ability to manipulate its data while in theatre.

Keith says:

If you have cellphone coverage you are not in the

If you pass cell towers all the time you ARE NOT in the Back Country.

GPS is not archaic. Could you imagine a jet having to rely on AT&T, Sprint or Nextel reliability to fix their position? How about a large vessel crossing the Pacific? Silly article! Where I live cellphone coverage is pretty good, but there is no way I would bet my life on it. Just too much real back country with no cellphone coverage up here.

P.S. That would be Alaska

Boyle M. Owl says:

Differential GPS

Waaaaay back in the beginning, GPS was not fuzzed, then the DoD decided to fuzz it. Along came Differential GPS where you adjusted for the fuzz by setting up on a known point, thus restoring the accuracy for the civilian user.

In other words, the market worked around it. With advances in electronics by the time of the death of Selective Availability in 2000, implementing Differential GPS had become trivial and inexpensive. This means that Selective Availability is TOAB. Tits on a bull.

And to quote Wikipedia “by this point DGPS had evolved into a system for providing more accuracy than even a non-SA GPS signal could provide on its own. “

It’s not the DoD lying to cover up “sekrit new tech”. It’s that the DoD sometimes knows when it can’t nail jello to a tree.


Jamie says:

GPS & cell towers

….With more and more location based services cropping up that don’t actually rely on GPS signals, such as the location-aware mobile search from Sprint and Microsoft which triangulates a caller’s position between cell towers, the access to accurate location data is becoming commonplace….

Actually, you’re dead wrong. Cell towers can only triangulate client devices with very precise timing. Where does that timing come from? GPS satellites.

Jim says:

Back when they reduced SA to zero, it wasn’t a recognition of the economic necessity of accurate GPS for non-military receivers, but rather recognition that there were the means to work around SA to get similar or better accuracy.

They announced a change in operational policy at the same time that simply said that when the US military was operating in an area, they would jam the commercial GPS signal into oblivion, while their military GPS receivers were equipped to ignore the jamming signal and still operate.

Jeffro says:

GPS & Cell Towers

I live in north-central Pennsylvania. The area is called the Pennslyvania Wilds. Not as remote as Alaska or most places out west. It is within a 3 hr drive for millions of folks from NY City, Philly, Pittsburgh, Buffalo and Cleveland. There are places in this area that you will not get cell phone signals for miles, even by car with external antennea. Hiking in this area, you would go for days sans signal. I monitor and band Bald Eagles in this area and GPS is vital for this and other activities i.e. Point Counting and Geocaching. At this point cell towers are not an option.

JKB says:

Just a system upgrade

Not much here. They’ve just reached an obsolescence of the SA capability as satellites have been retired. DoD has been implementing the capability for theater of operation scrambling of GPS while leaving the rest of the world’s GPS accuracy alone. Apparently, they now have a full constellation with the capability and no longer need the broad SA capability. Also, GPS couldn’t be approved for aviation until they could maintain a certain level of accuracy so this may allow GPS use by commercial planes and permit the retirement of LORAN and other long and medium range positioning systems.

See the statement from 2003 on this website of the USCG, who are the focal point for civilian GPS usage.

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