Selective Availability to stay "off"

[+Rockin Roddy]

It was reported today that the "selective availability" will continue to be turned off! Pres. Bush has agreed with the Pentagon to stop buying GPS satellite that can intentionally degrade the accuracy of civilian GPS units!

 

 

Taken from the article on my Comcast home page:

 

 

"While this action will not materially improve the performance of the system, it does reflect the United States' strong commitment to users by reinforcing that this global utility can be counted on to support peaceful civil applications around the globe," the Defense Department said in a statement.

 

The move coincides with the Air Force's solicitation to purchase the next generation of GPS satellites known as GPS III.

 

GPS devices are used to steer cars, fly planes or find missing skiers and hikers. They are used in emergency response, mining and construction and exploration for natural resources as well.

 

The government said its former practice of deliberately degrading the accuracy of GPS signals protected national security by preventing adversaries from obtaining precise location measurements. When the Clinton administration abandoned the practice in 2000, it said the government never again would degrade GPS signals, but the U.S. has said since then that it still can prevent civilian receivers in specific regions from using GPS signals.

 

 

No mention of CACHING???? What's wrong with these people??

[+Mofino]

I wonder if this will finally shut up my know it all brother in law. When I first got my GPS and started talking about geocaching he insisted that the government would soon degrade the signals again to prevent terrorist attacks. He got very argumentative about it. Like the terrorists needed GPS to attack us on 9/11?

 

Even if we were attacked again with civilian GPS signals degraded that would hinder rescue and emergency response crews trying to help. He didn't want to hear that. I think he just likes to argue...

 

Thanks for sharing this. Should make for an interesting "conversation" with him...

[+wesleykey]

More and more people use GPS now. Businesses track fleets of vehicles, people use them to drive in big cities, etc. I see it as becoming too useful for the common man to the point that the government would be wrong to take away what we have now.

[CoyoteRed]

Have terrorist ever relied on GPS for an attack? I'd think once you go within a certain range those two "big tall towers" were enough to guide them in. Also, and KBI might be able to confirm or refute this, I believe most modern planes have avoidance systems. I seem to recall that they said the terrorist had to fight the planes to actually get them to fly into the buildings. Could be BS, I don't know. If not, it's not as if you can just put a plane on autopilot and have it fly into the ground or building without some technical savvy.

 

I also have gotten into conversations about GPS-guided munitions. My retort has always been "why rely on machines when you have so many humans willing to die to do it instead?"

 

I believe most, if not all, terrorist attacks have been low tech, sophisticated maybe, but low-tech non-the-less.

[+nekom]

Have terrorist ever relied on GPS for an attack? I'd think once you go within a certain range those two "big tall towers" were enough to guide them in. Also, and KBI might be able to confirm or refute this, I believe most modern planes have avoidance systems. I seem to recall that they said the terrorist had to fight the planes to actually get them to fly into the buildings. Could be BS, I don't know. If not, it's not as if you can just put a plane on autopilot and have it fly into the ground or building without some technical savvy.

 

I also have gotten into conversations about GPS-guided munitions. My retort has always been "why rely on machines when you have so many humans willing to die to do it instead?"

 

I believe most, if not all, terrorist attacks have been low tech, sophisticated maybe, but low-tech non-the-less.

 

I've never heard of any kind of automatic avoidance system, but modern aircraft do have alarms for certain things, like excessive bank or sink rate, or ground proximity. The planes that hit the world trade towers, if i remember right, were going extremely fast, so they probably had warnings going off left and right, but I don't believe any of that will actually stop you from maneuvering the plane any which way you like. Airliners also have GPS systems of course. Since most terrorist attacks are crude homemade explosives, I can't see any way in which GPS would be able to aid terrorism. And even in the case of 9/11, the world trade towers were something so prominent you could visually navigate to them, you wouldn't need GPS to find them.

[+Confucius' Cat]

I don't believe the threat of terrorist attacks was ever the concern of selective availability. the concern was that a "sophisticated" enemy government could make a weapon similar to the Cruise missile and use our own satellites to guide it.

 

The big concern as i heard it was that the Cruise missle flys just a few feet above the ground and cannot be seen by radar. This requires VERY accurate position information (and most likely a lot of really good proximity sensors and such).

 

All my GPSr's still have considerable altitude ambiguity. I don't know if that is "built in" to the system or if it is just characteristic of consumer grade receivers, but I suspect it might be the "compromise" that allowed the government to be comfortable with turning off SA.

 

Even with great reception and long term "burn-in", my altitude readings often vary as much as 50 feet from the units' own readings in a stationary mode and about that much from published maps.

 

Then too it may just be that every "sophisticated" government already has a weapon system that can do the Cruise thing and does not need GPS.

[+KBI]

I've never heard of any kind of automatic avoidance system, but modern aircraft do have alarms for certain things, like excessive bank or sink rate, or ground proximity. The planes that hit the world trade towers, if i remember right, were going extremely fast, so they probably had warnings going off left and right, but I don't believe any of that will actually stop you from maneuvering the plane any which way you like.

That is accurate.

 

In those cockpits on September 11th there would have been, at the very least, a loud "TERRAIN, TERRAIN" warning repeated every few seconds. They probably heard other audible warnings such as "TOO LOW GEAR" (landing gear) as well.

 

Judging from the videos there may have also been high speed warnings going off -- a very loud clicking or beeping.

 

There are many such cockpit warnings designed into a modern airliner, but none of the warnings activated on Sept 11th would have actually been linked to the flight controls.

 

In fact, the only thing I can think of that is 'automatic' as far as any airliner actually taking control away from the pilot is a thing we call the "stick pusher:" a system that forces the control yoke forward (pushes the nose down) momentarily in the event of an impending aerodynamic stall. Aerodynamic stall refers to the sudden loss of lift that happens when a wing makes too high an angle with the air, usually as a result of insufficient airspeed (think of what happens when a water skier gets too slow in the water, only more abrupt.) An airplane can only fly so slowly before it stalls. Stalls are gentle (and fun) in a single-engine trainer, but in an airliner there is a warning that vigorously vibrates the controls to warn the crew, followed, if necessary, by the pusher. Pushing the airplane’s nose forward (downward) breaks the stall. The pilot can override the automatic pusher, and there is, of course, a convenient button that turns the pusher off in case it misbehaves.

 

A stall can happen at any altitude, and the pusher system only activates as a result of the wing’s relative angle to the air, NOT proximity to terrain or other obstructions. I doubt those airplanes had ANY active systems the terrorists/murderers would have needed to physically wrestle against during the WTC and Pentagon attacks.

 

Must have been a startlingly noisy cockpit, though. I hope those killers soiled their pants ... and then survived their impacts conscious, long enough to burn to death slowly ... if I may editorialize a bit.

 

Airliners also have GPS systems of course. Since most terrorist attacks are crude homemade explosives, I can't see any way in which GPS would be able to aid terrorism. And even in the case of 9/11, the world trade towers were something so prominent you could visually navigate to them, you wouldn't need GPS to find them.

That is also accurate.

 

Personally, however, I have mixed feelings about Selective Availability. While I know SA would not have stopped 9/11, and while I agree that switching it back on would be a huge blow to a GPS-dependent domestic economy in which the system has become deeply integrated (not to mention the effect it would have on your, and my, DNF-to-Find ratios) ... I have a big problem with the fact that it has become such a huge benefit to the global economy as a free gift to the world courtesy of U.S. Taxpayers like me. Why are we giving GPS away to the world? When are places like Canada, Russia, Germany, France, China, Iran, North Korea, etc. going to start helping us pay for all these billion-dollar satellites?

 

If there is ever a substantial chance the system will be used against us, I say: switch on the SA!! I’d be willing to give up Geocaching for a little while if it were necessary to slow or confuse an enemy who wanted to kill us, wouldn’t you?

 

Regardless of such a threat, however, I still have a big problem with the United States footing the entire bill for the world’s navigation system. Maybe we could come up with a way to distort the system anywhere that it doesn't directly benefit a US taxpayer. Maybe we could call it "Very Selective Availability."

 

Who knows ... maybe VSA already exists, and maybe it's a U.S. military secret. If so, that's even better.

[+rdaines]

American Merchant Marine vessels that travel throughout the World's oceans would probably not be happy with SA turned back on. Even recreational boaters who no longer have LORAN C available to them would probably not be happy about SA.

[+Confucius' Cat]

Do the oceanliners use GPS to dock?

 

I can't think of any other reason that a 200' error would be a big deal to them.

[+rdaines]

Do the oceanliners use GPS to dock?

 

I can't think of any other reason that a 200' error would be a big deal to them.

 

How about reefs, channels, inlets... it's not just wide open deep water out there. Not to mention (but I will) the locating of objects under the water, the trawls of traps, sunken vessels, other obstructions all which need fairly precise coordinates. Ever navigate in the fog or in a snow storm? An accurate GPS is a major blessing when you can't see the bow of your boat because the fog is so thick.

Edited September 22, 2007 by rdaines

[CoyoteRed]

 

Considering the length of the major oceangoing vessels you'd have to receivers on the bow, stern and long the beam to take advantage of 3m accuracy. Additionally, if a captain is routinely getting within 100m of objects without the direction of a pilot he'd probably be fired.

 

An accurate GPS is great. It doesn't replace sonar or radar, though.

[+rdaines]

True for commercial shipping but that still leaves recreational boaters who have grown to rely on GPS navigation. Plenty of people routinely cruise offshore and in the Caribbean. I, for one, don't want to break out the Ol' sextant.

[+Confucius' Cat]

Do the oceanliners use GPS to dock?

 

I can't think of any other reason that a 200' error would be a big deal to them.

 

How about reefs, channels, inlets... it's not just wide open deep water out there. Not to mention (but I will) the locating of objects under the water, the trawls of traps, sunken vessels, other obstructions all which need fairly precise coordinates. Ever navigate in the fog or in a snow storm? An accurate GPS is a major blessing when you can't see the bow of your boat because the fog is so thick.

emphasis added

 

"Grown to rely" is the gist of it. Like anything you use regularly, you are reluctant to give it up and never should have to do so without good reason.

 

In the past they have used buoys, lighthouses, bells, crow's nests, smaller guide boats...

 

i wonder how they did it in oh, say 1492?

 

I do remember talking to an amateur sailor in the late 80's and remarking how silly it was that we were still installing vehicle navigation tracking systems employing LORAN C after GPS had come into use and he said that boaters used LORAN C to check their GPS. Those were the very early days and I think the inaccuracies at that time were more than just SA.

 

Granted reactivating SA would be a major bummer, but it won't be the end of the world.

 

The only change we would need to make is to write better clues; something that should be done anyway if the hider is concerned about the impact of the cache- especially for micros.

 

I make most of my finds without a portable GPSr. If i can get within 300 feet and get a coarse direction, I will usually make the find.

Edited September 23, 2007 by Confucius' Cat

[+KBI]

It was reported today that the "selective availability" will continue to be turned off! Pres. Bush has agreed with the Pentagon to stop buying GPS satellite that can intentionally degrade the accuracy of civilian GPS units!

Here is the text of last week’s announcement from the Department of Defense. It is available at this link.

 

DoD Permanently Discontinues Procurement Of Global Positioning System Selective Availability

 

The Department of Defense announced today that it intends to stop procuring Global Positioning System (GPS) satellites with the capability to intentionally degrade the accuracy of civil signals.

 

This capability, known as Selective Availability (SA), will no longer be present in the next generation of GPS satellites.

 

Although the United States stopped the intentional degradation of GPS satellite signals by setting SA levels to zero in May 2000, this action to permanently remove SA eliminates a source of uncertainty in GPS performance that has been of concern to civil GPS users worldwide for some time. While this action will not materially improve the performance of the system, it does reflect the United States’ strong commitment to users by reinforcing that this global utility can be counted on to support peaceful civil applications around the globe.

 

The decision to remove the capability from the next generation GPS satellites was approved by the President after a recommendation from DoD. The move coincides with the U.S. Air Force’s solicitation to purchase the next generation of GPS satellites known as GPS III.

 

GPS is a dual-use, satellite-based system that provides accurate positioning, navigation and timing information to users worldwide. Originally developed by the Department of Defense as a military system, GPS has become a global utility. It benefits users around the world in many different applications, including aviation, road, marine and rail navigation, telecommunications, emergency response, resource exploration, mining and construction, financial transactions and many more.

 

Here is a link to the original White House press release of May 1, 2000 announcing the "switching off" of Selective Availability. (This is the event that launched The Great GPS Stash Hunt, now known as Geocaching.)

 

I found this part very interesting:

 

The decision to discontinue SA is coupled with our continuing efforts to upgrade the military utility of our systems that use GPS, and is supported by threat assessments which conclude that setting SA to zero at this time would have minimal impact on national security. Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened. This regional approach to denying navigation services is consistent with the 1996 plan to discontinue the degradation of civil and commercial GPS service globally through the SA technique.

I take this to mean that the US military has the ability to deny the full precision of the GPS system (introduce intentional error) to an enemy in one part of the world – say, the Middle East, – while leaving SA turned off everywhere else – say, wherever KBI is caching.

 

Cool.

 

More info: Selective Availability (Wikipedia)

[+Prime Suspect]

i wonder how they did it in oh, say 1492?

 

The answer to that would be "badly". It wasn't until an an accurate portable marine chronometer was invented (which allowed you to determine Longitude) that navigation on the seas became reliable. That didn't happen for another 300 years. Check out the book "Longitude" for a good read.

Edited September 23, 2007 by Prime Suspect

[+KBI]

Check out the book "Longitude" for a good read.

Thanks for a great book suggestion. That does sound like a good read.

 

 

As always, of course, there is Wikipedia:

 

Longitude

 

John Harrison

 

The only Longitude officially named for a Geocacher

[+rdaines]

Why do these discussions always have to go to the absurd extreme? Of course marine navigation can be done without the aid of electronics. The US Power Squadron (http://www.usps.org/newpublic2/index.html) a recreational boaters group, teaches all kinds of navigation techniques that just require a watch, compass, and chart. Silly statements like the 1492 aren't worth answering. If SA were turned back on I think it's effects on geocaching would not be of much concern but rather how it would affect the big business that has grown up around GPS aided navigation.

[+Team Cotati]

Have terrorist ever relied on GPS for an attack? I'd think once you go within a certain range those two "big tall towers" were enough to guide them in. Also, and KBI might be able to confirm or refute this, I believe most modern planes have avoidance systems. I seem to recall that they said the terrorist had to fight the planes to actually get them to fly into the buildings. Could be BS, I don't know. If not, it's not as if you can just put a plane on autopilot and have it fly into the ground or building without some technical savvy.

 

I also have gotten into conversations about GPS-guided munitions. My retort has always been "why rely on machines when you have so many humans willing to die to do it instead?"

 

I believe most, if not all, terrorist attacks have been low tech, sophisticated maybe, but low-tech non-the-less.

 

I've heard from a very reliable source that airplanes, even those really big ones, are quite capable of flying into the ground without the aid of an autopilot. Sometimes they even run into buildings, mountains and each other.

[+Team Cotati]

http://en.wikipedia.org/wiki/LORAN

[+Team Cotati]

http://en.wikipedia.org/wiki/SHORAN

[+klossner]

Additionally, we have demonstrated the capability to selectively deny GPS signals on a regional basis when our national security is threatened.

I take this to mean that the US military has the ability to deny the full precision of the GPS system (introduce intentional error) to an enemy in one part of the world – say, the Middle East, – while leaving SA turned off everywhere else – say, wherever KBI is caching.

No, they're talking about jamming the signal with ground-based or airborne gear. "Region" here means an area 100-200 miles across.