Imaginethesituation.Youaredrivingalongadesertoronamountain.Youhavenoideawhereyouare.Youpassedthelasthousetwohoursago.Thenyourcarbreaksdown.Itisnightanditiscold.Youhavenomobilephone.Whatdoyoudo?Well

　　Imaginethesituation.Youaredrivingalongadesertoronamountain.Youhavenoideawhereyouare.Youpassedthelasthousetwohoursago.Thenyourcarbreaksdown.Itisnightanditiscold.Youhavenomobilephone.Whatdoyoudo?WellnexttimetakeaGPSwithyou.Thisinventionmaybeabletohelpyou.Itisadevice(装置)whichusessatellites(卫星)tofindtheuser’sposition(位置).Itcanfindyourpositiontowithin20metres.AGPScannotstartyourcarbutatleastyouwillknowwhereyouare.

　　GPSwhichmeansGlobalPositioningSystemisasmallradioreceiver.Itlookslikeamobilephone.Itissometimesputintoawatchoratelephone.WealsofindGPSdevicesincarsplanesorboats.Someofthesedeviceshaveelectronicmapssoyouknowwhereyouare.Forexampleinacitytheycantellyouthenameofthestreet.

　　TherearethreepartstotheGlobalPositioningSystem.Thefirstpartisthereceiver.Youcanholditinyourhandorhaveitfixedintoyourcarplaneetc.Thesecondpartisagroupofsatellitesorbiting(环绕…运行)theEarth.Thereceivercontactsatleastfourofthesatellitesandcalculatesitsposition.Thethirdpartofthesystemisanetworkofgroundstations.Theyareallovertheworld.Theycontrolthesatellitesandmakesuretheyareworkingwell.

　　SomepeoplethinkthatinthefuturetheGPSwillbeascommonasthemobile.Theyarebecomingcheaperandmoreandmoreaccurate.AlsotherewillbenewusesfortheGPS.Perhapstheywillbecomelikewatches.Everyonewillhaveoneandyouwillneverbelostanywhere.

　　1.GPScanhelpyoufindyourpositioncan’tit?

　　2.WhatdoesaGPSlooklike?

　　3.HowmanythingsarementionedthatGPSdevicescanbeputinto?

　　4.WhydosomepeoplethinkGPSdeviceswillbepopularinthefuture?

　　5.Whatistheuseofgroundstations?

　　6.Whatistheauthor’spurposeofwritingthispassage?