测绘专业英语unit 20-24

UnitUnitUnitUnit20202020UnderstandingUnderstandingUnderstandingUnderstandingthethethetheGPSGPSGPSGPS（认识GPSGPSGPSGPS）WhatWhatWhatWhatIsIsIsIsGPS?GPS?GPS?GPS?（什么是GPSGPSGPSGPS）TheglobalPositioningSystem(GPS)operatedbytheU.S.DepartmentOFDefense(DOD)isasatellite-basedsystemthatcanbeusedtolocatepositionsanywhereontheearth.（全球定位系统（GPS），由美国国防部【DepartmentOFDefense】管理【operated运转、操作】，是一个基于人造卫星的系统，可以用来在全球任何地方定位）GPSprovidescontinuous(24hours/day),real-time,3-dimensionalpositioning,navigationandtimingworldwide.（GPS提供全世界范围内的全天候，实时，三维坐标，导航和授时的功能。）AnypersonwithaGPSreceivercanaccessthesystem,anditcanbeusedforanyapplicationthatrequireslocationcoordinates.（任何拥有一台GPS接收机的人都可以使用【access】这套系统，可以应用于任何需要位置坐标的工作中【beusedfor用来做】）TheGPSsystemconsistsofthreesegments:⑴thespacesegment:theGPSsatellitesthemselves,⑵thecontrolsegment,operatedbytheU.S.military,and⑶theusersegment,whichincludesbothmilitaryandcivilianusersandtheirGPSequipments.（GPS由【consistof由……组成】三个部分【segment部分、节】组成：⑴太空部分：GPS卫星自己，⑵地面控制部分，由美国军方【military原意军方的，这里词性转变了——军方n.】控制，⑶用户【user】部分，包括军方和民用【civilian民用；civil民用的—civilengineering】用户和他们的装备。）SpaceSpaceSpaceSpaceSegment:Segment:Segment:Segment:TheTheTheTheGPSGPSGPSGPSConstellationConstellationConstellationConstellation（太空部分：GPSGPSGPSGPS星座【或GPSGPSGPSGPS星群】）ThefirstGPSsatellitewaslaunchedbytheU.S.AirForceinearly1978.（第一颗GPS卫星由美国空军【AirForce】在1978年的早些时候发射的）Therearenow24satellitesorbitingtheearthatanaltitudeofabout10,900miles.（现在有24颗卫星在绕地球大约10900英里的高度运行）Thehighaltitudeinsuresthatthesatelliteorbitsarestable,preciseandpredictable,andthatthesatellites’motionthroughspaceisnotaffectedbyatmosphericdrag.（这么高的高度确保了卫星轨道是稳定、精确和可知的【predictable可预言的、可预知的】，并且确保了卫星穿过太空的运行不受到大气阻力【atmosphericdrag】的影响）Therearefoursatellitesineachof6orbitalplanes.（6个轨道平面【orbitalplane】中每个有4颗卫星。）Eachplaneisinclined55degreesrelativetotheequator,whichmeansthatsatellitescrosstheequatortiltedata55degreesangle.（每个平面相对于【relativeto】赤道面倾斜【incline】55度，这就意味着这些卫星以55度角穿过赤道）Thesystemisdesignedtomaintainfulloperationalcapabilityeveniftwoofthe24satellitesfail.（这套系统被设计成即使24颗卫星的2颗故障也能维持【maintain】全工作能力【operationalcapability】）These24satellitesmakeupafullGPSconstellation.（这24颗卫星组成了一个完整的GPS星座）TheGPSsatellitesarepoweredprimarilybysun-seekingsolarpanels,withnicadbatteriesprovidingsecondarypower.（GPS卫星主要由太阳定向【sun-seeking】太阳能电池板【solarpanels】提供动力【power供以动力】，镍镉蓄电池【nicadbatteries】提供备用【secondary第二的、副的】动力）EachGPSsatellitehasfouratomicclocksonboard,onlyoneofwhichisinuseatatime.ThesehighlyaccurateatomicclocksenableGPStoprovidethemostaccuratetimingsystemthatexists.（每一个GPS卫星有四个原子钟【onboard在船上，这里就是在卫星上的意思】，某一时刻只有一台在使用。这些高精度原子钟能够使GPS提供最准确的时间系统【thatexist持续、存在】）ControlControlControlControlSegment:Segment:Segment:Segment:U.S.U.S.U.S.U.S.DODDODDODDODMonitoringMonitoringMonitoringMonitoring（控制部分：美国国防部监控）TheU.S.DepartmentOfDefensemaintainsamastercontrolstationatFalconAirForceBaseinColoradoSprings.（美国国防部维持【maintain】了一个主控站，在科罗拉多斯普林斯【Springs】的佛肯【Falcon猎鹰】空军基地）TherearefourothermonitorstationslocatedinHawaii,AscensionIsland,DiegoGarciaandKwajalein.（还有4个监控站座落在夏威夷、阿松森岛【大西洋】、迭哥加西亚岛【印度洋】、卡瓦加兰岛【北太平洋】）TheDODstationsmeasurethesatelliteorbitsprecisely.（DOD站【指5个监控站】精确测量卫星轨道）Anydiscrepanciesbetweenpredictedorbitsandactualorbitsaretransmittedbacktothesatellites.（任何预报轨道和实际轨道之间的偏差【discrepancy差异】被传回卫星。）Thesatellitescanthenbroadcastthesecorrections,alongwiththeotherpositionandtimingdata,sothataGPSreceiverontheearthcanpreciselyestablishthelocationofeachsatelliteitistracking.（然后卫星可以广播这些改正值——连同【alongwith连同……一起】位置和时间数据一起，以便地球上的GPS接收机可以精确确定它所跟踪【track】的每个卫星的位置）UserUserUserUserSegment:Segment:Segment:Segment:MilitaryMilitaryMilitaryMilitaryandandandandCivilianCivilianCivilianCivilianGPSGPSGPSGPSUsersUsersUsersUsers（用户部分：军方和民用GPSGPSGPSGPS用户）TheU.S.militaryusesGPSfornavigation,reconnaissance,andmissileguidancesystems.（美国军方把GPS用在导航、侦察和导弹制导【missileguidance】系统上）CivilianuseofGPSdevelopedatthesametimeasmilitaryuseswerebeingestablished,andhasexpandedfarbeyondoriginalexpectations.（GPS的民用在军用建立起之时就发展起来了，并且已经发展的远远超过起初的期望）TherearecivilianapplicationsforGPSinalmosteveryfield,fromsurveyingtotransportationtonaturalresourcemanagementtoagriculture.（GPS的民用用途几乎用在每个领域，从测量到交通到自然资源管理到农业）MostcivilianusesofGPS,however,fallintooneofthreecategories:navigation,positioningandtiming.（然而，GPS的大部分民用用途，分为【fallinto】三种类型【category】：导航、定位和授时。）HowHowHowHowDoesDoesDoesDoesGPSGPSGPSGPSWork?Work?Work?Work?（GPSGPSGPSGPS如何工作）AGPSreceivercalculatesitspositionbyatechniquecalledsatelliteranging,whichinvolvesmeasuringthedistancebetweentheGPSreceiverandtheGPSsatellitesitistracking.（GPS接收机利用一项被称为卫星测距【satelliteranging】的技术，计算它自己的位置，涉及到GPS接收机到它所跟踪的GPS卫星的距离测量）Therange(therangeareceivercalculatesisactuallyapseudorange,oranestimateofrangeratherthanatruerange)ordistanceismeasuredaselapsedtransittime.（距离（接收机测的距离实际上是伪距，或者说是距离估值，而不是真实距离）是用传播时间来测的【elapse流逝v.】【本句意思是距离是用测时间的方法得到的】）Thepositionofeachsatelliteisknown,andthesatellitestransmittheirpositionsaspartofthe“messages”theysendviaradiowaves.（每个卫星的位置已知，并且卫星将它们的位置作为它们用无线电波发出的“讯文【导航电文】”的一部分传送【transmit】出去）TheGPSreceiveronthegroundistheunknownpoint,andmustco