GPS: The Invisible Utility - Page 44

C2 Proficiency · Open Cloze · Ready for C2 Proficiency Student's Book, Macmillan

For questions 1–8, read the text below and think of the word which best fits each gap. Use only one word in each gap.

Many of us are unaware of the (0) ___ to which our daily lives depend on the Global Positioning System (GPS), but the majority of people actually carry this technology everywhere they go because GPS is built into mobile phones. (1) ___ and every time we make a call, a GPS receiver determines our location by measuring the arrival time of signals from up to four space satellites which are (2) ___ orbit around the Earth. What's (3) ___ , GPS is a highly dependable time service. GPS satellites carry clocks synchronised (4) ___ within 1–3 milliseconds, and mobile networks make effective (5) ___ of these clocks to timestamp data, scramble it and then unscramble it at the other end. A glitch of just 100 thousandth of a second would (6) ___ rise to a myriad of problems. And it's not just phones. Stock markets, power grids, cloud computing – all of these rely on different locations agreeing on the time. They rely on GPS. Suffice to (7) ___ , if GPS ever went down, even just temporarily, we'd all be lost in more (8) ___ than one.

GPS: The invisible utility

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