GPS: selective availability Concepts

Pinpoint: How GPS Is Changing Our World

by Greg Milner · 4 May 2016 · 385pp · 103,561 words

very well, though—through no fault of Trimble’s. As the new generation of GPS satellites was launched, post-Challenger, the Pentagon was finally able to implement its plan to make civilian GPS worse. It was called selective availability, or SA. The operating software for the new satellites intentionally dithered the signal, distorting

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removed from the constellation, SA would become universal. SA was switched on. Almost immediately, the Pentagon had no choice but to turn it off. Selective availability officially began in April 1990, the same month Trimble delivered the promised thousand Trimpacks. Four months later, Iraq invaded Kuwait—coincidentally, on the same day

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to the ongoing encryption of the military’s GPS signal, a practice denoted by the acronym AS, short for anti-spoofing. (Well, almost nobody—Ashtech’s “Kiss Your AS Goodbye” corporate ads suggested a responsible opposing viewpoint.) Left unsettled was the status of selective availability. The Pentagon kept the policy in place

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their receivers gave more accurate readings. What ultimately doomed selective availability was the existence of a supplementary positioning technique called DGPS—the D is for “differential.” DGPS is not

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refinement of the readings from nearby GPS receivers. In a DGPS network, one or more continuously operating GPS receivers broadcasts the correction to any GPS receivers in the area authorized to receive the correction. These receivers adjust their calculations accordingly. Even absent the intentional errors of selective availability, DGPS is a useful way to

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a DGPS network administered by the Coast Guard, while the official military policy was to degrade civilian GPS through selective availability. With each passing year in the 1990s, the continued development of differential GPS methods made selective availability look increasingly worthless—a point Javad Ashjaee made by running an Ashtech ad featuring the Mona Lisa

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eliminating SA because “any enemy of the United States sophisticated enough to operate GPS-guided weapons will be sophisticated enough to acquire and operate differential systems.” It was ultimately the lure of an untapped market that finally banished selective availability. Brad Parkinson publicly commented that not only was the policy ineffective, it

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compared to the rapid growth of the commercial GPS industry—worth $2 billion in 1996, and growing at an annual rate of 20 percent. That year, President Bill Clinton, in consultation with the Department of Defense, announced in a presidential decision that the selective availability policy would end within ten years. At

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more accurately than they do now,” Clinton said in a statement. The death of selective availability was catalytic for the GPS industry. Within two weeks, Garmin’s sales were up 40 percent and Magellan’s retailers were setting company records. Gauging the overall

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in place for decades, but it did not provide nationwide coverage. GPS was free, but risky. The satellite constellation was still not complete, and steps would need to be taken to correct for the dithering effects of the Pentagon’s selective availability program. But it was the best option. AT&T, the

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P code vs. C/A code of, 76–77, 82, 83, 97 pseudorandom digital code of, 55 selective availability (SA) of, 94–95, 99–100 “spoofing” experiments with, 147–52, 157–58, 161, 167–69 GPS Systems Group, 203 Gran Sasso Mountain, 155–56 Gravesend Bay, 249 gravity, 131, 231–32, 245,

Accessory to War: The Unspoken Alliance Between Astrophysics and the Military

by Neil Degrasse Tyson and Avis Lang · 10 Sep 2018 · 745pp · 207,187 words

system had achieved its full complement of twenty-four satellites; by 2003 there were twenty-eight. In 2000 the practice known as selective availability—the intentional degradation of publicly available GPS signals, implemented for reasons of national security—had been terminated. For a while at least, everyone, civilian or military, would always and

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Chief Reports Finding No New Weapons,” transcript, New York Times, Jan. 28, 2003. 34.GPS.gov, “Selective Availability,” www.gps.gov/systems/gps/modernization/sa/; “Data from the First Week Without Selective Availability: GPS Fluctuations Over Time on May 2, 2000,” www.gps.gov/systems/gps/modernization/sa/data/. Reported maximum accuracy varies from 2.66 meters (just under nine

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Nazism: Secret Aryan Cults and Their Influence on Nazi Ideology: The Ariosophists of Austria and Germany, 1890–1935. New York: New York University Press, 1992. GPS.gov. “Selective Availability.” Grafton, Anthony. “Girolamo Cardano and the Tradition of Classical Astrology: The Rothschild Lecture, 1995.” Proceedings of the American Philosophical Society 142:3 (Sept. 1998

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, 99 GLONASS system (Russia), 160, 337–38, 362, 363, 516n GPS III, 337 ionosphere and, 333 in Iraq War, 336, 346, 348 jamming of, 333, 515n, 516n NAVSTAR Global Positioning System, 278, 332, 335–36 overview, 158, 332–33, 339–40 selective availability, 336 smart bombs and, 335 global security, 14–15 GLONASS

You Are Here: From the Compass to GPS, the History and Future of How We Find Ourselves

by Hiawatha Bray · 31 Mar 2014 · 316pp · 90,165 words

A signal, misstating the time on each satellite’s atomic clock and the satellites’ precise location in space. Thanks to this gimmick, known as “selective availability,” a civilian GPS device would be accurate to within only 100 meters, or 330 feet—about the length of a football field.25 This is adequate for

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Charged with securing safe passage through the nation’s ports, this federal agency wanted civilian GPS to be as precise as the military version. So the coast guard found a way to defeat selective availability—a system called differential GPS. The agency built dozens of radio transmitters at fixed, precisely mapped locations, covering the

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the backing of shipping companies and the US Congress. Besides, the coast guard showed the futility of trying to dumb down GPS. A determined enemy would find a way past selective availability. “The cat’s out of the bag,” air force major Steve Gabriel told a journalist in 1993. “If you can

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go around. Desperate to get the technology to the troops, the US military bought thousands of civilian GPS units, which at the time were mostly being used by backpackers, hunters, and land surveyors. Thanks to selective availability, these units were not nearly as accurate as the military kind. The Pentagon finally ordered that

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selective availability be switched off, and in August 1990 it was. Instantly, civilian GPS units became almost as accurate as their military cousins. It was too

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good to last; with Saddam Hussein safely defeated by July 1991, selective availability was reactivated and civilian GPS restored to its previous level of

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tractors to precisely plant and harvest their land. And although car navigation systems based on GPS were being developed by the mid-1990s,29 the Pentagon’s selective-availability mandate ensured that they were not nearly good enough to provide the turn-by-turn driving directions we now take for granted. Businesses

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with GPS. GLONASS could be used by anyone in the world; each satellite broadcast both a military and a civilian signal, and the civilian signal was surprisingly accurate, capable of pinpointing the user’s location to within about sixty feet. There was one big difference—the Russians never bothered with selective availability.

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would pay for access, but in exchange they would be able to measure locations to within a fraction of an inch. Neither system would include selective availability, like the American GPS network. Indeed, the decision to build Galileo was driven in large part by European fears that America might degrade

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persuading the Europeans to modify their system to ensure it would be interoperable with GPS and also that it would use a military frequency that would not interfere with GPS transmissions. By 1996 the United States decided that selective availability was more trouble than it was worth. In 1996 the Clinton administration announced it

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would shut down selective availability at an unspecified future date. Concern about competition from GLONASS and Galileo

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US taxpayers. Around the world many commercial GPS users feared that the United States would tamper with the accuracy of the service during some future conflict. Yet even after the terrorist attacks of September 11, 2001, and the subsequent wars in Iraq and Afghanistan, selective availability was not reactivated. In 2007 the

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United States officially pledged that selective availability would never be used again. In fact, in 2014 it will begin launching a new generation of GPS satellites that lack the capacity for selective capability, because the necessary

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hardware will no longer be installed.33 Eliminating selective availability was not just good news for navigators. It was a boon to the world’s

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time to millions of GPS receivers on the ground. The system’s control center constantly updated the satellites’ atomic clocks, ensuring their accuracy. Around the world, people could simply tune in to the satellites as they passed overhead. This could not be done in the era of selective availability, but switching off

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.com/news/politics/0,1283,51130,00.html. 32. Roftiel Constantine, GPS and Galileo: Friendly Foes? (Maxwell Air Force Base, AL: Air University Press, 2007), 9. 33. US Department of Defense, “DoD Permanently Discontinues Procurement of Global Positioning System Selective Availability,” September 18, 2007, www.defense.gov/Releases/Release.aspx?ReleaseID=11335

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(GPS) system birth of, 91–93 cell phones and, 113–118, 135–137 civilian use of, 98, 105, 106–112 compasses and, 119 differential, 108–109 distortion and, 107, 111 emergency services and, 113–115 GSM and, 116 in-car, 91–92, 110 mapping and, 119 military, 107–110 selective availability and

Maphead: Charting the Wide, Weird World of Geography Wonks

by Ken Jennings · 19 Sep 2011 · 367pp · 99,765 words

, the error was intentional, baked into the signal for reasons of national security. But by the late 1990s, this scrambling, euphemistically called “selective availability,” was becoming obsolete. The military had figured out how to localize its GPS jamming in places where secrecy was an issue, and a new ground-based technology called Differential

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GPS was allowing civilians to improve on satellite data anyway. So President Bill Clinton ordered “selective availability” to be turned off altogether, and in the spring of 2000, White House science advisor Neal Lane announced the big moment

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previously. In March, he’d been snowmobiling to the peak of Mount Saint Helens, trying to follow a trail he’d taken once before. But selective availability led him one hundred yards off course, and he shot out over an ice ridge he wasn’t expecting. “I slid down one side of

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the latitude and longitude of that spot on an Internet newsgroup for GPS users. That first announcement was startlingly prophetic, envisioning in detail not just a single celebratory stunt but an ongoing international treasure hunt in embryo: Now that SA [selective availability] is off, we can start a worldwide Stash Game! With non

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–14, 116–19 sandwich, Earth, 240–42 Saturday Night Live, 38, 223–24 Scott, Robert Falcon, 90, 205 Scripps National Spelling Bee, 124, 146–47 selective availability, 187 Seoul, South Korea. See under Jennings, Ken Seven Cities of Gold, 85 Sexmoan, Philippines, 70 sexuality, 70–71, 77 Shackleton, Ernest, 90 Shultz, George

Peers Inc: How People and Platforms Are Inventing the Collaborative Economy and Reinventing Capitalism

by Robin Chase · 14 May 2015 · 330pp · 91,805 words

were lost in a city. In 1996, President Bill Clinton announced that the U.S. government would stop its intentional degradation of the civilian GPS signal—called Selective Availability—to change the resolution from a hundred meters down to twenty meters by 2000. And in September 2007, it stopped degrading the signal at

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, 2014, https://medium.com/message/what-does-the-facebook-experiment-teach-us-c858c08e287f. CHAPTER 7: FOR THE PEOPLE 1. Jeffrey K. McGee, “Global Positioning System Selective Availability: Legal, Economic, and Moral Considerations,” School of Advanced Military Studies, U.S. Army Command and General Staff College, Fort Leavenworth, KS, November 23, 1999. 2

The Perfectionists: How Precision Engineers Created the Modern World

by Simon Winchester · 7 May 2018 · 449pp · 129,511 words

hundred fifty feet horizontally and three hundred feet vertically. Yet that restriction, what was called selective availability, was scrapped in 2000 on the orders of President Clinton. Ever since then, users worldwide have been able to use GPS receivers in everything from their cars to their telephones to wristwatches to handheld devices taken

The Next Great Migration: The Beauty and Terror of Life on the Move

by Sonia Shah

, 212–13, 293. “Giant flukes happen” Marris, “Tree Hitched a ride.” Defense Department stopped adding a jitter to its GPS “Frequently Asked Questions About Selective Availability: Updated October 2001,” GPS.gov, https://www.gps.gov/systems/gps/modernization/sa/faq/. allowed people to track the once-undetectable movements Cheshire and Uberti, Where the Animals Go. “we

The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies

by Erik Brynjolfsson and Andrew McAfee · 20 Jan 2014 · 339pp · 88,732 words

Survey of Canada, October 7, 1997), http://pubs.usgs.gov/of/1997/of97-269/brodaric.html. 23. Selective Availability (National Coordination Office for Space-Based Positioning, Navigation, and Timing, February 17, 2012), http://www.gps.gov/systems/gps/modernization/sa/. Chapter 5 INNOVATION: DECLINING OR RECOMBINING? 1. Henry Southgate, Many Thoughts of Many Minds

The Pentagon's Brain: An Uncensored History of DARPA, America's Top-Secret Military Research Agency

by Annie Jacobsen · 14 Sep 2015 · 558pp · 164,627 words

enemy access to this kind of precise targeting information, the system was originally designed with an offset feature built in, called selective availability (SA). If an individual were able to access the GPS system with a private receiver, the information would be offset by several hundred feet. Over the next ten years, the

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effort to keep the United States at the forefront of the burgeoning new industry, in May 2000 President Clinton discontinued the selective availability feature on GPS, giving billions of people access to precise GPS technology, developed by DARPA. To Albert Wohlstetter, working on the DARPA analysis in the mid-1970s, the fusion of various

Sextant: A Young Man's Daring Sea Voyage and the Men Who ...

by David Barrie · 12 May 2014 · 366pp · 100,602 words

remarkably generous spirit, the U.S. government made GPS freely available to the public, worldwide, in 1983, though—for reasons of national security—only the U.S. military had access to the most accurate positional data until May 2000, when the system of “selective availability” was ended. The Russians have developed a similar