电子与通信技术专业英语（第6版）课件 项目16 Global Positioning System (GPS)

刘骋蔡静主编电子与通信技术专业英语（第6版）高职高专电子信息类“十三五”规划教材EnglishonElectronicandTelecommunicationTechnology03UnitⅢCommunicationTechnologyLesson16GlobalPositioningSystem(GPS)

UnitⅢNewWordsterrestrial [tə'restriəl] adj. 地球的，地上的latitude ['lætitju:d] n. 纬度longitude ['lɔndʒitju:d] n. 经度trilateration [,trailætə'reiʃən] n. 【测】三边测量（术）redundant [ri'dʌndənt] adj. 多余的segment ['seɡmənt] n. 段；部分orbit ['ɔ:bit] n.&v.轨道，常轨；绕轨道而行NewWordsdelay [di'lei] n.&v.耽搁，延迟ionosphere [ai'ɔnəsfiə] n. 电离层pseudo ['sju:dəu] adj. 假的，冒充的sequence ['si:kwəns] n. 序列，继起的事，顺序multiple ['mʌltipl] adj. 多样的，多重的access ['ækses] n. 通路，进入，使用之权encrypt [in'kript] v. 加密，将……译成密码GPSistheGlobalPositioningSystem.GPSusessatellitetechnologytoenableaterrestrialterminaltodetermineitspositionontheEarthinlatitudeandlongitude.Lesson16GlobalPositioningSystem(GPS)ChineseTranslationofTextsGPS是全球卫星定位系统。GPS使用卫星技术，能使地面终端确定它在地球上的经度和纬度的位置。第16课

全球定位系统（GPS）ChineseTranslationofTextsGPSreceiversdothisbymeasuringthesignalsfromthreeormoresatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals（Fig.16-1）.ChineseTranslationofTexts接收器同时测量来自三个或三个以上的卫星的信号，并通过这些信号的传播时间来确定位置（图16－1）。ChineseTranslationofTextsGPSoperatesusingtrilateration.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthelengthsofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.ChineseTranslationofTexts

GPS的工作使用三边测量法。三边测量是指在未知点两侧有两个或两个以上的已知点，与未知点呈虚拟的三角形，通过测量未知点到已知点的边长来确定未知点。ChineseTranslationofTextsIntheGPSsystem,thetwoknownpointsareprovidedbytwoGPSsatellites.Thesesatellitesconstantlytransmitanidentifyingsignal.TheGPSreceivermeasuresthedistancetoeachGPSsatellitebymeasuringthetimeeachsignaltooktotravelbetweentheGPSsatelliteandtheGPSreceiver.ChineseTranslationofTexts在GPS中，两个已知点由两个全球定位系统卫星提供。这些卫星不断传送一个确定的信号。GPS接收机通过测量每一个信号在GPS卫星和GPS接收机之间传播的时间来测量其距离。ChineseTranslationofTextsGPSoperatesusingtrilateration.TheGPSsystemisdividedintothreesegments:TheSpaceSegmentTheControlSegmentTheUserSegmentChineseTranslationofTexts全球卫星定位系统分为三个部分：空间部分控制部分用户部分ChineseTranslationofTextsGPSusestwenty-oneoperationalsatellites,withanadditionalthreesatellitesinorbitasredundantbackup.GPSusesNAVSTARsatellitesmanufacturedbyRockwellInternational.EachNAVSTARsatelliteisapproximately5meterswide(withsolarpanelsextended)andweighsapproximately900Kg.ChineseTranslationofTexts

GPS使用21颗运行卫星，轨道中另外还有3颗后备卫星。全球定位系统利用由罗克韦尔国际制造的导航卫星。每一个导航卫星约5米宽（包括延太阳能发电板的长度），重量大约900公斤。ChineseTranslationofTextsGPSsatellitesorbittheearthatanaltitudeofapproximately20,200km.EachGPSsatellitehasanorbitalperiodof11hoursand58minutes.ThismeansthateachGPSsatelliteorbitstheEarthtwiceeachday.ChineseTranslationofTexts

GPS卫星的轨道离地区的距离约为20200公里。每个GPS卫星绕轨道一周的时间为11小时58分钟。这意味着每一个GPS卫星每天绕地球两次。ChineseTranslationofTextsThesetwenty-foursatellitesorbitinsixorbitalplanes,orpaths.ThismeansthatfourGPSsatellitesoperateineachorbitalplane.Eachofthesesixorbitalplanesisspacedsixtydegreesapart.Alloftheseorbitalplanesareinclinedfifty-fivedegreesfromtheEquator.ChineseTranslationofTexts这24颗卫星有6个轨道面，或路径，这意味着每个轨道面有4个GPS卫星工作。6个轨道面的每个之间呈60度隔开。所有这些轨道面都偏离赤道倾斜55度。ChineseTranslationofTextsInorderforGPStrackingtowork,itisnecessarytohavebothaccesstotheGlobalPositioningSystemandhaveaGPSreceiver(Fig.16-2).TheGPSreceiverisabletoreceivesignalsthataretransmittedbyGPSsatellitesorbitingoverhead.OncethesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncanbecalculated.ChineseTranslationofTexts

GPS为了进行跟踪，既要访问全球定位系统，还要有一个全球定位系统接收机（图16－2）。全球定位系统接收机能收到上方绕轨道运行的全球定位系统卫星传送的信号。一旦这些卫星传送的信号被全球定位系统接收机收到，位置及其他信息如速度和方向等就能计算出来。ChineseTranslationofTextsThereceivercontainsamathematicalmodeltoaccountfortheseinfluences,andthesatellitesalsobroadcastsomerelatedinformationwhichhelpsthereceiverinestimatingthecorrectspeedofpropagation.Certaindelaysources,suchastheionosphere,affectthespeedofradiowavesbasedontheirfrequencies,dualfrequencyreceiverscanactuallymeasuretheeffectsonthesignals.ChineseTranslationofTexts接收机包含有一个数学模型来计算这些信息的影响，卫星也传播一些相关的信息以帮助接收机正确地估算传播速度。电离层等一些原因，会影响不同频率的无线电波的速度,双频接收机能测量它们对信号的影响。ChineseTranslationofTextsInordertomeasurethetimedelaybetweensatelliteandreceiver,thesatellitesendsarepeating1,023bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthetwosequencesmatch.ChineseTranslationofTexts为了测量卫星和接收机之间的时间延迟,卫星重复发送1,023字节长的伪随机序列；接收机建立一完全相同的序列和移动它直到两序列匹配。ChineseTranslationofTextsDifferentsatellitesusedifferentsequences,whichletsthemallbroadcastonthesamefrequencieswhilestillallowingreceiverstodistinguishbetweensatellites.ThisisanapplicationofCodeDivisionMultipleAccess,CDMA.ChineseTranslationofTexts不同卫星使用不同的序列，这样，当不同的卫星发送相同频率的信号时，接收机能够区别它们。这就是码分复用（CDMA）的应用。ChineseTranslationofTextsTherearetwofrequenciesinuse:1575.42MHz(referredtoasL1),and1227.60MHz(L2).TheL1signalcarriesapubliclyusablecoarse-acquisition(C/A)codeaswellasanencryptedP(Y)code.TheL2signalusuallycarriesonlytheP(Y)code.ChineseTranslationofTexts有两个频率GPS被使用：1575.42MHz（称之为L1频率）和1227.60MHz((L2频率)，L1信号携带一个可公开使用的粗码(C/A)，和一个加密码P(Y)。L2信号通常只携带P(Y)码。ChineseTranslationofTextsNoteslatitudeandlongitude经纬度如：Oneusedtorepresentaunitofmeasurement,suchasfeetorminutesinlatitudeandlongitude.

用来代表衡量单位用来代表某一测量单位，如经度或纬度上的英尺或分1Notes如：Nothingmaketheearthseemsospaciousastohavefriendatadistance;theymakelatitudeandlongitude.没有一件事情比得上有朋在远方更使这地球显得如此广大的了；他们构成纬度，也构成经度。1Notes如：GPSistheGlobalPositioningSystem.GPSusessatellitetechnologytoenableaterrestrialterminaltodetermineitspositionontheEarthinlatitudeandlongitude.GPS是全球卫星定位系统。GPS使用卫星技术，能使地面终端确定它在地球上的经度和纬度。1Notessimultaneouslyadv.同时地（联立地）如：Thatcannotbesimultaneouslytrue;mutuallyexclusive.互相矛盾的，不能同时成立的；互斥的2Notes如：Agroupofthreebitsorthreepulses,usuallyinsequenceononewireorsimultaneouslyonthreewires.3个二进制位或3个脉冲组成的一组，通常按时间顺序出现在一根导线上或同时出现在3根导线上。2NotesGPSreceiversdothisbymeasuringthesignalsfromthreeormoresatellitessimul-taneouslyanddeterminingtheirpositionusingthetimingofthesesignals.GPS接收器同时测量来自3个或3个以上的卫星的信号，并通过这些信号的传播时间来确定位置。2NotesNAVSTARsatellites导航卫星3NotesRockwellInternational罗克韦尔国际公司例如：GPSusesNAVSTARsatellitesmanufacturedbyRockwellInternational.译文：全球定位系统采用由罗克韦尔国际公司制造的导航卫星。4Notesequatorn.（地球或天球的）赤道；（平分球形物体的面的）圆thecelestialequator：天球赤道theearth’sequator：地球赤道themagneticequator：地磁赤道例如：Alloftheseorbitalplanesareinclinedfifty-fivedegreesfromtheequator.译文：所有这些轨道面都偏离赤道倾斜55°。5Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.GPSusescomputertechnologytoenableaterrestrialterminaltodetermineitspositionontheEarth.b.GPSreceiversdothisbymeasuringthesignalsfromonlyonesatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals.c.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthetemperatureofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.d.EachNAVSTARsatelliteisapproximately50meterswideandweighsapproximately90kg.Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.GPSusescomputertechnologytoenableaterrestrialterminaltodetermineitspositionontheEarth.b.GPSreceiversdothisbymeasuringthesignalsfromonlyonesatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals.c.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthetemperatureofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.d.EachNAVSTARsatelliteisapproximately50meterswideandweighsapproximately90kg.FFFFExercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.e.InorderforGPStrackingtowork,itisnecessarytohaveaccesstotheGlobalPositioningSystembuthaveaGPSreceiverf.IntheGPSsystem,thetwoknownpointsareprovidedbyoneGPSsatellites.g.TheGPSreceiverisabletoreceivesignalsthataretransmittedbystarsorbitingoverhead.h.EventhesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncannotbecalculated.Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.e.InorderforGPStrackingtowork,itisnecessarytohaveaccesstotheGlobalPositioningSystembuthaveaGPSreceiverf.IntheGPSsystem,thetwoknownpointsareprovidedbyoneGPSsatellites.g.TheGPSreceiverisabletoreceivesignalsthataretransmittedbystarsorbitingoverhead.h.EventhesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncannotbecalculated.FFFFExercises2.Matchthefollowingtermstoappropriatedefinitionorexpression.a.GPSb.CDMAc.orbitalperiodof11hoursand58minutesd.GPSsystemisdividedinto1.Space,ControlandUserSegment2.CodeDivisionMultipleAccess3.GlobalPositioningSystem4.orbitstheEarthtwiceeachdayExercises2.Matchthefollowingtermstoappropriatedefinitionorexpression.a.GPSb.CDMAc.orbitalperiodof11hoursand58minutesd.GPSsystemisdividedinto1.Space,ControlandUserSegment2.CodeDivisionMultipleAccess3.GlobalPositioningSystem4.orbitstheEarthtwiceeachdayExercises3.Fillinthemissingwordsaccordingtothetext.a.Inordertomeasurethetimedelaybetween

and

,thesatellitesendsarepeating1,023bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthe

match.b.Thesesatellitesconstantlytransmitanidentifying

.c.TheGPSreceivermeasuresthe

toeachGPSsatellitebymeasuringthetimeeachsignaltooktotravelbetweenthe

andtheGPSreceiver.d.GPSuses

operationalsatellites,withanadditional

inorbitasredundantbackup.Exercises3.Fillinthemissingwordsaccordingtothetext.a.Inordertomeasurethetimedelaybetweensatelliteandreceiver,thesatellitesendsarepeating1,023bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthetwosequencematch.b.Thesesatellitesconstantlytransmitanidentifyingsignal.c.TheGPSreceivermeasuresthedistancetoeachGPSsatellitebymeasuringthetimeeachsignaltooktot