Questions 11–21 are based on the following passage and supplementary material.
This passage is excerpted from Dan Glass, What Happens if GPS Fails?” © 2016 by The Atlantic.
Despite its name, the Global Positioning System is not about maps; it’s about time. Each satellite in the constellation (24 are needed, plus the U.S. has several spares) has multiple atomic clocks on board, Line 5 synchronized with each other and to Coordinated Universal Time (UTC)—the time standard used across the world—down to the nanosecond. The satellites continually broadcast their time and position information down to Earth, where GPS receivers in Line 10 equipment from iPhones to automated tractors acquire signals and use the minuscule differences in their arrival time to determine an exact position. While GPS was initially conceived to aid navigation, globally synchronized time is now a much Line 15 more critical function of the system. Telecom networks rely on GPS clocks to keep cell towers synchronized so calls can be passed between them. Many electrical power grids use the clocks in equipment that fine-tunes current flow in overloaded networks. The finance Line 20 sector uses GPS-derived timing systems to timestamp ATM, credit card, and high-speed market transactions. Computer network synchronization, digital television and radio, Doppler radar weather reporting, seismic monitoring, even multi-camera sequencing for film Line 25 production—GPS clocks have a hand in all. What if all these flying clock radios were wiped out, and everything on the ground started blinking 12:00? According to Mike Lombardi, a meteorologist at the National Institute for Standards and Technology, Line 30 “Nobody knows exactly what would happen; Since so many of these technologies were designed specifically with GPS in mind, the unsettling truth, he says, is “there’s no backup:” The bulk of a more promising, comprehensive Line 35 backup system already exists, right here on the ground. After the sextant but before GPS, navigators around the world used Long Range Aids to Navigation, or “LORAN; a terrestrial system of transmitters and receiving equipment first developed during WWII. Line 40 By the mid-1990s, Loran “tower chains” provided coverage for North America, Europe, and other regions in the Northern Hemisphere. Its use declined in favor of the much finer accuracy of GPS after it became available for civil use in 1995, but the U.S. Line 45 Coast Guard continued working on an improved system using the existing infrastructure. If adopted, “Enhanced” LORAN, or eLoran, could provide positioning accuracy comparable to GPS. Broadcast at hundreds of thousands of watts, the signal is virtually Line 50 un-jammable, and unlike GPS, can even be received indoors, underwater, and in urban or natural canyons. It also turns out that eLoran can provide a UTC time signal with sub-microsecond time resolution across a large geographical area. Line 55 The technology is available—the Coast Guard demonstrated a working prototype last year—so why isn’t America using it? John Garamendi, a California congressman, asked this question at a July 2015 congressional hearing on the Federal Line 60 Radionavigation Plan, the nation’s primary planning document for position, navigation, and timing (PNT). “There are two kinds of time; he opened, “real time … and then federal time, which seems to be the forever time The eLoran system was identified as a backup 15 Line 65 years ago, and here we are, federal time, not yet done’ Why is the sense of urgency among decision-makers so out of sync? Could some of it be similar to why people delay backing up their computers even though they’ve been telling themselves to for Line 70 weeks? How do we decide, when presented a risk with unknown odds, when it’s time to sacrifice time and resources to prevent it? Now is a critically important time to answer that question, as the world has actually been given odds on Line 75 another, even more catastrophic risk than GPS failure: destruction of the electrical power infrastructure itself. On July 23, 2012, a billion-ton cloud of electrified gases blasted off the far side of the sun at over six million miles per hour. According to professor Daniel Baker Line 80 at University of Colorado, this coronal mass ejection (CME) “was in all respects at least as strong as the 1859 Carrington Event; referring to the strongest solar storm ever recorded, which set fire to telegraph stations and caused auroras down to Cuba. As was Line 85 widely reported two years ago, if the 2012 CME had occurred one week later, it would have hit Earth.
11. The main purpose of the passage is to
- present a problem with a current technology and highlight a potential solution.
- provide an overview of how clocks and satellites determine distance and location.
- analyze the negative impacts of certain technologies across various industries.
- praise developers for their ability to answer the hard questions.
Ans:/Explanation
Ans:A
12. As used in line 13, “conceived” most nearly means
- designed.
- understood
- absorbed.
- accepted.
Ans:/Explanation
Ans:A
13. The primary purpose of the question in lines 26–28 (“What… 12:00”) is to
- introduce a problem.
- correct a misconception.
- reconsider a perspective.
- undermine an idea.
Ans:/Explanation
Ans:A
14. Which of the following best characterizes Lombardi’s attitude toward “flying clock radios” (line 26)?
- He is confident about their ability to handle a multitude of tasks.
- He is concerned about how they will interact with the eLoran systems.
- He is annoyed that no one knows exactly how they work.
- He is worried that they have no replacement systems in case of emergency.
Ans:/Explanation
Ans:D
15. Which choice provides the best evidence for the answer to the previous question?
- Line 25 (“GPS clocks…all”)
- Line 30 (“Nobody…happen”)
- Lines 30–33 (“Since…backup”)
- Lines 34–35 (“The bulk…ground”)
Ans:/Explanation
Ans:C
16. As used in line 34, “bulk” most nearly means
- dimensions.
- mass.
- majority.
- totality.
Ans:/Explanation
Ans:C
17. According to John Garamendi, the reason America isn’t using the eLoran system even though the technology is available is that
- the system doesn’t use real time.
- government approval takes longer than the development of the technology.
- federal decision-makers are scared to change systems.
- solar storms threaten the system.
Ans:/Explanation
Ans:B
18. Which choice provides the best evidence for the answer to the previous question?
- Lines 48–51 (“Broadcast…canyons”)
- Lines 64–65 (“The eLoran…done”)
- Lines 70–72 (“How do…it”)
- Lines 73–76 (“Now is…itself”)
Ans:/Explanation
Ans:B
19. According to figure 1, which group is closest in percentage to the percentage of users 18–29 in May 2011 who got location-based information on their smartphones?
- Ages 50+ in Feb 2012
- Ages 50+ in May 2011
- Ages 30-49 in Feb 2012
- Ages 18-29 in Feb 2012
Ans:/Explanation
Ans:A
20. Which statement is supported by figure 2?
- Less than a third of North American GPS revenue comes from the Automotive industry.
- GPS revenues for Surveying/Mapping are less than GPS revenues for Precision Agriculture.
- GPS devices are less important for the Aviation industry than they are for the Marine industry.
- The Automotive and Marine industries make up a greater percentage of North American GPS revenues than the rest of the industries combined
Ans:/Explanation
Ans:D
21. Which additional information, if presented in figure 2, would be most useful in evaluating the statement in lines 13–15 (“While… system”)?
- The total number of GPS devices sold
- The number of individuals in each industry using GPS devices
- The percentage of the industry that relies on the GPS devices
- The amount of revenue in dollars for each industry
Ans:/Explanation
Ans:C