测绘专业英语

GeomaticsisarelativelynewscientifictermcreatedbyPollockandWrightin1969,withtheintentionofcombiningthetermsgeodesyandgeoinformatics.ItincludesthetoolsandtechniquesusedinSurveyingandMapping,RemoteSensing(RS),Cartography,GeographicInformationSystems(GIS),GlobalNavigationSatelliteSystems(GNSS,i.e.,GPS,Glonass,Galileo,Compass),Photogrammetry,Geography,Geosciences,ComputerSciences,InformationScienceandvariousspatialobservationtechnologies,landdevelopmentandenvironmentalsciences,etc.测绘学是一种相对较新的科学术语由波洛克和赖特在1969年提出，目的是将大地测量学与地理信息学结合起来。它包括的工具和技术应用于测绘、遥感(RS)、地图学、地理信息系统(GIS)、全球导航卫星系统(GNSS,即。、GPS、Glonass、伽利略、北斗),摄影测量、地理学、地球科学、计算机科学、信息科学和各种空间观测技术、土地开发、环境科学等。Surveyingmaybedefinedasthetechnologyandscienceofthestudyofearth’sshapeandsize,aswellasmakingmeasurementsoftherelativepositionsofnaturalandman-madefeatureson,aboveorbelowtheearth’ssurface,andrepresentingtheseinformationinanalogformsascontouredmapsorsections,paperplanorchart,orasfiguresinreporttables,orindigitalformasathreedimensionalmathematicalmodelstoredinthecomputer.测量的技术和科学可以定义为研究地球的形状和大小,以及测量位于地球外表上或者低于或者高于地球外表的自然的或人造的物体的相对位置,并将这些信息以模拟形式的波状外形的地图、剖面图、论文方案、图表、数据报告表中呈现或以数字形式存储在计算机三维数学模型中。Surveysarethetechnologiesofmeasuringhorizontalandverticaldistancesbetweenobjects,measuringanglesbetweenlinesorthedirectionoflines,anddeterminingtheelevationsofthepoints.Aftertheactualmeasurementsofsurveys,mathematicalcalculationsaremadetodeterminethedistances,angles,directions,locations,elevations,areas,andvolumesfromsurveyingdata.Thenmuchsurveyinginformationisportrayedgraphicallyinformsoftheconstructionmaps,profiles,cross-sectionsanddiagrams.测绘学是测量物体之间的水平和垂直距离,测量直线之间的角度或直线的方向,测量点位的高度的技术。在实际测量后,需要根据测量数据进行数学计算来确定距离,角度,方向,位置,海拔,地区和体积。然后测量信息就以地图、剖面图、横断面图和图表等图形形式描绘出来。Theequipmentsavailableandmethodsapplicableformeasurementsandcalculationshavechangedtremendouslyinthepastdecade.Traditionalequipmentsformeasurements:Optical(electronic)Theodolite,Tapes,ElectronicDistanceMeasurement(EDM),levels,etc.Modernequipments:Aerialphotogrammetry,satelliteobservation,RemoteSensing(RS),inertialsurveying,andlaserrangingtechniques,etc.Atthesametime,therelativelyeasyaccesstocomputersofallsizefacilitatestherigorousprocessingandstorageoflargevolumesofdata.可用的设备和适用于测量和计算的方法在过去十年发生了巨大变化。传统的测量设备:光学〔电子〕经纬仪、磁带、电子测距(EDM)、水准尺等。现代设备:航空摄影测量、卫星观测、遥感(RS)、惯性测量,激光测距技术,等等。同时,电脑的相对广泛应用促进了严格处理和存储大量数据的过程。Withthedevelopmentofthesemoderndataacquisitionandprocessingsystems,thedutiesofthesurveyorshaveexpandedbeyondthetraditionaltasksofthefieldworkoftakingmeasurementsandtheofficeworkofcomputinganddrawing.Surveyingisrequirednotonlyforconventionalconstructionengineeringprojects,mapping,andpropertysurveys,butisalsousedincreasinglybyotherphysicalsciences,suchasgeology,geophysics,biology,agriculture,forestry,hydrology,oceanographyandgeography,etc.随着现代数据采集和处理系统的开展,测量员的职责已经大大超出了传统的野外测量工作和内业计算和绘图工作。测量不仅适用于传统的建筑工程工程、地图学和土地权属调查,也越来越多的适用于其他物理科学,如地质、地球物理、生态学、农学、林业学、水文、海洋、地理等。TheessentialworkofsurveyingistodetermineaccuratelythepositionofthefeaturesonthesurfaceoftheEarth(horizontalsurveying),andtheelevationsofthefeatures(verticalsurveying),oracombinationofboth.Althoughdifferentsurveysarefordifferentpurposes,thebasicoperationsinclude:measurements(fieldwork),computationsandmapping(officework).Fromanotherpoint,theworkofsurveyingiseithertodeterminethelocations(three-dimensionalcoordinates)ofgroundfeaturesanddrawingallkindsofmaps,ortomarkoutthedesignedbuildingsorstructuresinmapsattheirproposedpositions.测量的根本工作是确定地球上物体的准确位置(水平测量)和高度(垂直测量),或两者的结合。虽然不同的调查是为了不同的目的,根本操作包括:测量(野外),计算和绘图(内业)。从另一个角度,测量的工作是确定地球表现上物体的位置(三维坐标)和绘制各种地图,或在地图上的建筑物、构筑物中标定他们的位置。Surveyingoperationsinclude:(1)designofsurveyingproceduresandselectionofequipments;(2)acquisitionandstorageofdatainthefields;(3)reductionoranalysisofdataintheofficeorinthefiled;(4)preparationofmapsorotherdisplaysinthegraphicalornumericalformsneededforthepurposeofsurvey;(5)layoutofmonumentsandboundariesinthefields,aswellasprovidingcontrolsurveyingforconstruction.测量操作包括:(1)测量过程的设计和测量仪器的选择;(2)野外数据的采集和存储;(3)在办公室或野外分析和处理数据;(4)准备测量所需的地图或其他以图形或数字形式的呈现的图形;在野外埋设标石和边界,进行施工控制测量。Performanceofthesetasksrequiresafamiliaritywiththeusesofsurveyingequipmentsandtechniques,knowledgeoffundamentalsofthesurveyingprocess,andknowledgeofvariousmeansbywhichdatacanbepreparedforpresentation.Definitionsofcontrolsurveyinganddetailsurveying:(1)Controlsurveyingisreferredtothemeasurementsofcontrolpoints,whicharewellspacedintheformofnetworkandplaycontrollingrolesinsurveyarea.(2)Detailsurveyingisreferredtotheworkofmeasuringtheterrainfeaturesaroundeachcontrolpoint.这些任务的完成需要熟练使用测量设备和技术,测量过程的根底知识和在地图上展绘数据的各种知识。控制测量和碎部测量的定义:(1)控制测量的测量控制点,以网络的形式分布在测区并在测区起控制作用。(2)碎部测量是测量每个控制点周围的地形特征。Theworkofsurveyingshouldfollowsomebasicproceduresorrules:(1)Controlsurveyingshouldbefirstlycarriedout,andthendetailsurveying.(2)Theworkofsurveyingshouldbeconducedfromthewholetotheparts.(3)High-precisionsurveyingcontrolsthelow-precisionsurveying.(4)Eachstepofsurveyingworkhasacheck.Thesebasicproceduresorrulescanhelptodividesurveyingareaintodifferentmapunits,reducetheerroraccumulation,ensuretheprecisionofmapping,andspeedupthemappingprocess.测量工作应该遵循根本的程序和规那么:(1)控制测量应首先进行,然后进行碎部测量。(2)测量的工作应该是从整体到局部。(3)高精度等级测量控制低精度等级测量。(4)步步要检核。这些根本的程序或规那么可以把测量区域划分为不同的地图单元,减少误差积累,保证了地图的精度,加快制图过程。Surveyshavemanydifferentbranches,suchasgeodeticsurveying,planesurveying,engineeringsurveying,topographicsurveying,cadastralsurveying,minesurveying,etc.1.GeodeticsurveyingGeodeticsurveyingisreferredtothemeasurementandrepresentationoftheEarth’sshapeandsize,gravityfieldandgeodynamicphenomena(suchaspolarmotion,Earthtidesandcrustalmotion),andestablishmentofcontrolnetworksoflargeareasforothersurveys.调查有很多不同的分支,如大地测量、平面测量,工程测量,地形测量、地籍测量、矿山测量学等。1、大地测量学大地测量是测量和表征地球的形状和大小,重力场和地球动力学的现象(如极移、地球潮汐和地壳运动),建立用于其他大面积测量的控制网络的学科。Ingeodeticsurveying,largeareasoftheEarth’ssurfaceareinvolvedandthetrueshapeoftheEarthmustbetakenintoaccount,andthestationsarenormallylongdistancesapart,andmorepreciseinstrumentsandsurveyingmethodsarerequiredforthistypeofsurveying.Ingeodeticsurveying,theshapeoftheEarthisthoughtofasaspheroid,althoughitisnotreallyaspheroidinatechnicalsense.在大地测量学中，由于地球外表的大局部地区都有涉及，所以地球的真实形状必须考虑进去,由于站点之间的分隔距离较远,所以需要更精密的仪器和测量方法。在大地测量学中，地球的形状被认为是一个球体,虽然在理论意义上并不是一个球体。Therefore,distancesmeasuredonornearthesurfaceoftheEartharenotalongstraightlinesorplanes,butonacurvedsurface.Widelyspacedandpermanentmonumentsareusedasthebasisforcomputinglengthsanddistancesbetweenrelativepositions.allowancesaremadefortheearth’sminorandmajordiametersfromwhichareferencespheroidisdeveloped.Thesebasicpointswithpermanentmonumentsarecalledgeodeticcontrolpoints,whichsupporttheproductionofconsistentandcompatiblereferencecoordinatesforothersurveyingandmappingprojects.因此,在地球外表或者地球附近所测的距离并不是沿直线或平面的,而是在一个曲面上。广泛放置的永久标石可以作为计算长度和相对点位之间距离的根底。参考椭球面是根据地球的大小半径的容许差来建立的。这些带有永久标石的根本点被称为大地控制点,为其他的测量工作提供固定坐标和相对坐标。PlanesurveyingThetypeofsurveyinginwhichthemeansurfaceoftheearthisconsideredaplane,orinwhichthecurvatureoftheearthcanbedisregardedwithoutsignificanterror,generallyiscalledplanesurvey.Thetermisusedtodesignatesurveyworkinwhichthedistancesorareasinvolvedareoflimitedextent.平面测量在这种测量中地球平均外表被认为是一个平面,或在没有较大误差的情况下地球曲率可以被忽略,这种测量通常被称为平面测量。这种测量都用于指定的距离和面积在有限范围内的测量工作。Withregardtohorizontaldistancesanddirections,alevellineisconsideredmathematicallystraight,thedirectionoftheplumblineisconsideredtobeplaneangles.Inplanesurveying,formulasofplanetrigonometry,algebra,andanalyticalgeometryareusedtomakecomputations.Forsmallareas,preciseresultsmaybeobtainedwithplanesurveyingmethods,buttheaccuracyandprecisionofsuchresultswilldecreaseastheareasurveyedincreasesinsize.对与水平距离和方向,水平线在数学上被认为是直的,铅垂线的方向被认为是平面角。在平面测量中，平面三角公式、代数、解析几何是用来计算的。对小区域,平面测量方法可以获得精确的结果,但结果的准确度和精度将随着测区的面积增大而降低。Thereareclosecooperationbetweengeodeticsurveyandplanesurvey.Thegeodeticsurveyadoptstheparametersdeterminedbymeasurementsoftheearth,anditsownresultsareavailabletothosewhomeasuretheearth.Theplanesurveysaregenerallyconnectedtothecontrolpointsofthegeodeticsurveys.大地测量和平面测量之间有密切的联系。大地测量采用参数取决于所测量的地球平面,并且测量结果可被其他测量地球的人使用。平面测量通常与大地测量的控制点有关。3.TopographicsurveyingTopographicsurveysaremadetodeterminetheconfiguration(relief)ofthesurfaceoftheearth,locatethenaturalandartificialfeaturesthereon,andproducemaps,plansorsectionstosuitablescales.Manynaturalandartificialfeaturessuchasrelief,hydrography,vegetation,road,trails,buildings,canalsandboundarylineshavetoberepresentedbyconventionalsymbolsinatopographicmap.3.地形测量地形测量是用来确定地球外表形状,确定自然和人工物体的位置,并生成地图,选定平面图和区域图的适宜的比例尺。许多天然和人工物体,比方地貌、水文、植被、道路、小径、建筑物、运河和边界线必须由传统的地形图符号在地形图中表示。Topographicmapshaveheightinformationeitherasspotheightsorascontours,andtheirscalesaredifferentranges.Topographicmapshaveamultitudeofuses,suchasnavigation,recreation,geographicalandgeologicalstudy,military,exploration,etc.地形图上有点位高度表示的高程信息和以等高线表示的高程信息,他们的比例尺范围不同。地形图有多种用途,如导航、娱乐、地理和地质研究、军事、勘探等。4.EngineeringsurveyingEngineeringsurveysarereferredtoallthesurveysrequiredindesign,constructionandmanagementstagesofengineeringconstructions.Forexample,inthestageofsurveyanddesign,large-scaletopographicalmapsorplansarerequiredasabasisfordesign,thentheproposedpositionofanynewitemoftheconstructionmustbemarkedoutonthegroundbothinplaneandheight,theseoperationsgenerallytermedsetting工程测量工程测量是指建筑设计、工程建设和工程建设的管理阶段的所有测量工作。例如,在勘察设计阶段,大比例尺的地形图或设计作为设计的根底,并且提出任何新的建设工程的点位必须在平面上放样出平面位置和高度,这些操作通常称为放样。settingout,andfinally,as-builtsurveysanddeformationmonitoringareoftenrequired.Thedesignandconstructionofnewroutes,e.g.roads,andrailways,thecalculationsoftheareasandvolumesoflandarealsotheaspectsofengineeringsurveys.放样,最后竣工调查和变形监测通常是必需的。新路线的设计和施工,如公路,铁路,计算区域大小和土方量也属于工程测量。5.CadastralsurveyingCadastralsurveysarereferredtotheworkofmakingmeasurementsandplottingthemeasurementstoproduceplansofpropertyboundariesforlegalpurposes.Inmanycountriestheregistrationsofownershipoflandsarebasedonsuchplans.地籍测量地籍测量是指进行测量和绘制符合法律用途的合法边界。在许多国家登记的土地的所有权是基于这样的平面图。6.MineSurveyingMinesurveyingisconcernedwithmeasurementsofsurfaceandundergroundmines,obtainingdataindigitalformandmakinggraphicalrepresentationforprospectingmineraldeposits,constructingminesandexploitingminerals.Afewcenturiesago,minesurveyingisextensivelydevelopedforthedeterminationoftheboundariesoftheminingclaims.Theearlyperiodofminesurveyingmaybeconsideredastheartofrunningundergroundtraverses.矿山测量学矿山测量学是测量外表和地下矿山、以数字形式获取数据,使图形标绘勘探矿藏,矿山建设和开采矿产。几个世纪前,矿山测量学广泛开展是为了采矿勘界的目的。矿山测量学的早期可能被视为布设地下导线。However,asitdeveloped,minesurveyingincluded,apartfromtechniquesofminesurveying,theminesurveyinginstrumentation,thegeometryofmineralresources,studyoftectonics,etc.Alltheseaspectsofminesurveyingaremadefortheprecisionofgeologicalexploration,aswellasthesafetyandefficiencyinworkingamine.Astheprogresshasbeenmadeinthemethodsofminesurveying,theminesurveyorsareusingthegyro-theodolite,high-precisiontheodolitesandopticalrangefinderstosolveoftheproblemsoforientationandconstructionofreferencenetworks.然而,随着它的开展,矿山测量学,除了矿山测量技术、矿山测量仪器,矿产资源的几何构造和技术研究等。矿山测量的所有这些方面构成地质勘探精度,以及矿井工作的平安性和效率。矿山测量学方法的进步,矿山测量员使用陀螺经纬仪、高精度经纬仪和光学测距仪来解决定向和参照网络的建设等问题。Self-adjustinglevelsandlasershaverecentlybecomeverypopulartogivelinesandgradesandcheckonthedirectionsofmines,andprovidecontrolforsuchoperationsasmineshaftequipment,layingrailwaytracks,installingconveyors,puttingthroughpipelinesandothers.Moreover,newtechniquesandinstrumentsaremadeforplottingminegraphicsandpreparingmineplansandlongitudinalandtransversesections.自动安平水准仪和激光水准仪最近变得非常流行在施工方样和坡度以及检核矿井方向等方面,并为矿井设备操作提供控制,铺设铁轨,安装输送机,放样管道和其他事物。此外,新技术和仪器是用来铺设井筒和绘制矿井平面图和纵和横向断面图的。Theearliestsurveyswereforthepurposeofestablishingtheboundariesofland,andsuchsurveysarestillimportantworkofmanysurveyors.Everyconstructionprojectofanymagnitudeisbasedtosomedegreeuponmeasurementstakenduringtheprogressofasurveyandisconstructedaboutlinesandpointsestablishedbythesurveyors.Asidefromlandsurveys,practicallyallsurveysofprivateandpublicnaturesareofassistanceintheconception,design,andexecutionofengineeringworks.最早的调查是为了建立土地的边界,这样的测量工作仍是测量员的重要工作。任何规模的建设工程都是在某种程度上基于测量以及测量员所放样的点线。除了土地调查,几乎所有的私有和公共性质调查是概念、设计、工程和执行工作的辅助设备。1.4DevelopmentsofSurveying1.SurveyingtechniquesHistorically,distancesweremeasuredbydifferentmeans,forinstancetapesmadeofsteelorinvarwerepulledtauttoreducesaggingandslacktomeasurehorizontaldistances.Additionally,attemptingtomeasureupaslope,thesurveyorsmighthavetouseincrementslessthanthetotallengthofthetape.Horizontalanglesweremeasuredusingacompass,whichwouldprovideamagneticbearing.Thistypeofinstrumentwaslaterimproved,withmorecarefullyscribeddiscsprovidingbetterangularresolution,aswellasthroughmountingtelescopeswithreticlesformore-precisesightingatopthedisc.从历史上看,距离测量的方式有很多,例如使用拉紧的钢尺或铟瓦尺减少下垂和松弛来测量水平距离。此外,为了测量斜坡,测量员可能使用增量法而不是总长度的钢尺。使用带有磁轴承的罗盘测量水平角度。这种类型的仪器后来有所改善,更仔细地刻划度盘从而提供更好的角分辨率,以及通过望远镜的十字刻划丝来更精确的瞄准度盘的顶部。High-accuracytransitsortheodoliteswereusedforthiswork,andanglesbetweenobjectsweremeasuredrepeatedlyforincreasedaccuracy.Historically,thesimplestmethodformeasuringheightswasusingairpressureasanindicationofheightwithanaltimeter(basicallyabarometer).Butsurveyingrequiresgreaterprecision.Avarietyofmeans,suchaspreciseleveling(alsoknownasdifferentialleveling),havebeendevelopedtodothis.Withpreciseleveling,aseriesofmeasurementsbetweentwopointsaretakenusingalevelinstrumentandalevelingrod.高精度经纬仪被用于这项工作,通过增加物体之间角度测量次数来增加准确性。测量高度的历史上,最简单的方法是使用带有空气压力的高度计指示高度(本质上是一个气压计)。但测量需要更高的精度。各种手段,如精密水准测量(也称为微分水准),已经开发出来。精密水准测量,两点之间的测量工作通过一系列仪器和水准尺进行。Triangulationisanothermethodofhorizontallocationwaswidelyusedinthepastyears.Aslongastheyarevisiblefromoneoftheoriginalobjects,withthetriangulationmethod,distancesanddirectionsbetweenobjectsatgreatdistancefromoneanothercanbedetermined.AmoremoderninstrumentisaTotalStation,whichisatheodolitewithanElectronicDistanceMeasurement(EDM).Sinceitsintroduction,totalstationhasmadethetechnologicalshiftfrombeingoptical-mechanicaldevicetobeingfullyelectronic。三角测量是过去被广泛应用的一种测量水平位置的方法。只要他们从最初的对象是可见的,三角测量方法,两个较远物体之间的距离和方向可以确定。更现代的仪器是全站仪,它是一个经纬仪与电子测距仪(EDM)的组合。全站仪引入以来,全站仪技术已经从光学机械设备完全转变为电子的。ModernTotalStationsnolongerrequireareflectororprism(usedtoreturnthelightpulses)tomeasuredistances,theyarefullyroboticandcanevene-mailpointdatatotheofficecomputer.Withtheadvancementofsatellitepositioningtechnology,thespeedandprecisionofsurveyingaregreatlyincreasedbyusingGlobalPositioningSystem(GPS).BecauseGPSsystemsdonotworkwellinareaswithdensetreecoverorconstructions,TotalStationsarestillusedwidelyalongwithothertypesofsurveyinginstruments.Nowrobotic-guidedTotalStationsallowsurveyorstogatherprecisemeasurementswithoutextrasurveyorstolookthroughandturnthetelescopeorrecorddata.现代全站仪不再需要一个反射器或棱镜(用于返回光脉冲)来测量距离,他们完全自动化甚至可以以电子邮件的方式发送数据点到办公室的电脑。随着卫星定位技术的开展,测量的速度和精度大大增加通过使用全球定位系统(GPS)。因为GPS系统在茂密的树木覆盖的地区或建筑密集区工作性能不好,全站仪仍与其他类型的测量仪器一同广泛使用。现在智能全站仪允许测量员在没有额外的测量员进行检核、调整棱镜和记录数据的情况下，进行精确测量。Chapter2DatumsofSurveying2.1Geoidandreferenceellipsoid2.2Mapprojection2.3Datumsandcoordinatesystem2.1Geoidandreferenceellipsoid大地水准面和参考椭球面TheEarth’sphysicalsurfaceisarealityuponwhichthesurveyingobservationsaremadeandpointsarelocated.However,duetoitsvariabletopographicsurfaceandoverallshape,itcannotbedefinedmathematicallyandsopositionscannotbecomputedonitssurface.Itisforthisreasonthatinsurveysoflimitedextent,theEarthistreatedasflatandplanetrigonometryusedtodefineposition.地球的物理外表是一个测量观测地形和放样点位的真实外表。然而,由于其变化的地形外表和整体形状,它不能按照数学方法定义,所以点位也不能在其外表计算。正是因为这一原因,在调查范围有限的情况下,地球呗认为是平的,平面三角用来定义点的位置。Iftheareaunderconsiderationisoflimitedextent,orthogonalprojectionofthisareaontoaplanesurfacemayresultinnegligibledistortion.Planesurveyingtechniquescouldbeusedtocapturefielddataandplanetrigonometryusedtocomputeposition.However,iftheareaextendedtoalargeareabeyondlimitationandtreatedasaflatsurfacetheeffectoftheearth’scurvaturewillproduceunacceptabledistortion.如果考虑到测区的面积是有限的,这一地区的正交投影在平面上可能产生的变形是可以忽略不计的。平面测量技术可以用来捕获野外数据和平面三角测量用于计算点的位置。然而,如果测区面积扩大到超出一定限制的区域,被当作一个平面，由于地球曲率的影响将产生不可接受的变形。Therefore,amathematicalmodeloftheearthisneededtorepresenthorizontalpositionsandelevationsonmaps.Assuch,itisnecessarytodefineamathematicalsurfacethatapproximatestotheshapeoftheareaunderconsiderationandthenfitandorientateittotheEarth’ssurface.Suchamathematicalsurfaceisreferredinsurveyingasa‘referenceellipsoid’.因此,需要地球的一个数学模型来表示地图上点的水平位置和高度。因此,必须定义一个接近考虑区域的数学平面,然后拟合并定位到地球外表。这样的数学外表在测量上被称为参考椭球体。(1)GeoidSincethephysicalsurfaceoftheEarthcan’tbeusedasacomputationalsurface,ameansealevelsurfaceisinstinctivelytakenintoconsideration.Meansealevel(MSL)isdefinedastheaverageleveloftheoceansurfaceforallstagesofthetideafterlongperiodsofobservations.Byextendingtheearth’sMSLthroughthelandmass,anequipotentialsurfaceapproximatelyatMSLwouldbeformed.Suchasurfaceiscalledthe‘geoid’.大地水准面因为物理地球外表不能被用作计算面,平均海平面是本能地考虑。平均海平面被定义为长时间观察所有阶段潮后的平均海平面。将地球的平均海水面扩展到大陆上,接近于平均海水面的等势面大约会形成。这样一个外表被称为“大地水准面”。ItcouldbeimaginedthatatrenchisdugacrossthecountrieslinkingtheAtlanticandPacificoceans.Ifthetrenchisfilledwithseawater,thesurfaceofthewaterinthetrenchwouldrepresentthegeoid.它可以想象,在各个国家挖的连接大西洋和太平洋的槽。如果槽充满海水,槽里水的外表代表大地水准面。Thusbydefinition,thegeoidisanequipotentialsurfaceoftheEarthgravityfieldthatmostcloselyapproximatesthemeanseasurface.Thegeoidisonlyatheoreticalsurface,whichisperpendicularateverypointtothedirectionofgravity.Theshapeofgeoidcanbeactuallymeasuredwhichisbasedongravitydatacollectedworldwide.因此根据定义,大地水准面是一个最接近平均海水面的地球重力场的等势面。大地水准面只是一个理论外表,它上边的每一个点垂直指向重力的方向。大地水准面的形状可以由在全球范围内收集的重力数据来计算。AlthoughthegravitypotentialiseverywherethesameandthesurfaceissmootherthanphysicalsurfaceoftheEarth,itstillcontainsmanyirregularitieswhichrenderitunsuitablemathematicallocationofplanimetricposition.TheseirregularitiesarethoughttobeduetomassanomaliesthroughouttheEarth.Thegeoidremainsimportanttothesurveyor,asitisthesurfacetowhichallterrestrialmeasurementsarerelated.虽然重力势处处都是一样的,重力势外表比物理地球外表光滑,它还包含了许多不规那么的形状使它呈现不适合数学平面位置的点位。这些不规那么形状被认为是由于在整个地球质量异常引起的。对于测量员来说大地水准面仍然是重要的,因为它是与所有陆地测量相关的外表。Asthedirectionofthegravityvectoriseverywherenormaltothegeoid,itdefinesthedirectionofthesurveyor’splumb-bobline.Thusanyinstrumentwhichishorizontalizedbymeansofaspiritbubblewillbereferencedtothelocalequipotentialsurface.ElevationsarerelatedtotheequipotentialsurfacepassingthroughMSL.Suchelevationsorheightsarecalledorthometricheights(H)andarethelineardistancesmeasuredalongthegravityvectorfromapointtotheequipotentialsurfaceasareferencedatum.因为重力的方向向量在大地水准面上到处都是正常的,可以用它定义测量员的铅锤线的方向。因此通过水准气泡整平的任何仪器将会引用到当地等位面。高程与穿过平均海水面的等位面有关。海拔或高度等被称为正常高(H),它是一个重力位上的点到等势面所测量直线距离来作为参考数据。(2)ReferenceEllipsoidTheellipsoidisamathematicalsurfacewhichprovidesaconvenientmodeloftheEarth,andcanbestmeettheneedsofaparticulargeodeticdatumsystemdesign.Itisrepresentedbyanellipserotatedaboutitsminoraxisandisdefinedbyitssemi-majoraxisandflattening.Althoughtheellipsoidisaconceptandnotaphysicalreality,itrepresentsasmoothsurfaceforwhichformulascanbedevelopedtocomputeellipsoidaldistance,azimuthandellipsoidalcoordinates.(2)参考椭球体椭球是数学的外表给地球提供了一个方便的模型,并能最好的满足特定的大地基准系统的需求设计。它是由椭圆旋转短轴和被定义为它的长半轴和扁率。虽然椭球是一个概念,而不是现实的物理外表,它表示一个平滑的外表在上边可以用公式计算大地距离,方位角和大地坐标。Duetothevariableshapeofthegeoid,itisnotpossibletohaveaglobalellipsoidofreferenceforusebyallcountries.由于变量的形状大地水准面,不可能有一个全球所有国家使用参考椭球。Thebest-fittingglobalgeocentricellipsoidistheGeodeticReferenceSystem1980(GRS80),whichhasthefollowingdimensions:globalgeocentricellipsoidsemi-majoraxisa=is6378137.0m全球地心椭球semi-minoraxisb=is6356752.314mflatteningɑ=1：298.257全球最正确拟合的地球椭球是全球地心大地参考椭球系统1980(GRS80),参数如下:长半轴a=6378137.0米短半轴b=6356752.314米压扁ɑ=1：298.257EquatorialAxisEquatorialAxisPolarAxisNorthPoleSouthPoleEquatoraba=6378137m北极

b=6356752.3m

equatorialdiameter=12756.3km

polardiameter=12713.5km

equatorialcircumference=40075.1km

surfacearea=510064500km2WGS[世界大地坐标系统]84椭球:a=6378137mb=6356752.3m赤道直径=12756.3公里极地直径=12713.5公里赤道周长=40075.1公里面积=510064500平方公里Therelationshipofallthreesurfaceswhichareterrain,geoidandellipsoidisillustratedinthefigurebelow.地球外表、大地水准面、参考椭球面三者之间的关系见下列图。TheorthometricheightHistheheightwithreferencetotheMSL,whereasthegeodeticheighthistheheightreferencedtoellipsoid.正高H是参考面到平均海水面的高度,而大地高度h参考面到参考椭球的高度。Terrain地势GroundpointA地面点ATerrain地势GroundpointA地面点AHHhGeoidhGeoid大地水准面BN=h-HBN=h-Hreferenceellipsoidreferenceellipsoid参考椭球面ThequantityN,theheightofthegeoidabovethereferenceellipsoidortheperpendiculardistancebetweenthegeoidandthereferenceellipsoidatapoint,isusuallycalledthegeoidalheight(geoidundulation).数量N,大地水准面高于参考椭球体的高度或某点大地水准面和参考椭球体面之间的垂直距离,通常被称为大地水准面高度(大地水准面起伏)。Oncethegeoidisdetermined,thedifferencebetweenthesurfacesoftheellipsoidandgeoidanywhereinthecountrycanbecomputed.Surveyorsusedtoworkingwithspiritlevelhavereferencedorthometricheights(H)tothe‘average’surfaceoftheearth,asdepictedbyMSL.ThesurfaceofMSLcanbeapproximatedbythegeoid.一旦大地水准面确定下来,在全国的任何地方都可以计算参考椭球面和大地水准面之间的距离。测量员用水准仪测量正高(H)也就是点到地球平均外表的高度,如平均海水面。平均海水面可以近似为大地水准面。TheheightoftheMSLabovethegeoidiscalledtheseasurfacetopography(SST).Itisaverydifficultquantitytoobtainfromanymeasurements.Consequently,itisnotyetknownveryaccurately.平均海水面的高度高于大地水准面的地方称为海面地形(SST)。这是一个非常难以通过任何测量获得的量。因此,它是还没有完全确定。GPSheightsarereferencedtotheellipsoid,amathematicalmodelthatdoesnotphysicallyexist.Thismodel,doesnotagreewithMeanSeaLevel.ThatmeanstheheightofapointdeterminedfromGPSisnotthesameasitssealevelelevationasdeterminedbyleveling.GPS高是由参考椭球得到的,参考椭球是物理上不存在的数学模型。这个模型,与平均海平面不拟合。这意味着决定某点的GPS高与它的由水准尺测得的平均海水面高程不一样。Thesummaryoftherelationshipsamongheightsystemscanbeillustratedbelow:(1)MSLelevationisroughlyequivalenttoorthometricheight(H),thetechnicalnameforheightabovethegeoid.Thegeoidis,forallintentsandpurposes,thesameasMSL.高度系统之间的关系可以总结如下:平均海水面高度相当于正高(H),是大地水准面以上高度的专业名称。大地水准面是,从某种意义上,和平均海水面一样的。(2)Geoidalheight(N)istheseparationbetweenthegeoidandtheellipsoid(sometimescalledGeoidalseparation).Itcanbeplusorminus.Anegativegeoidalseparationindicatesthatthegeoidisbelowtheellipsoid,andapositiveseparationisabove.(3)Ellipsoidalheight(h)isthedistanceaboveorbelowtheellipsoid(plusorminus).Ellipsoidalheightisalsocalledgeodeticheight.(2)大地水准面高度(N)是大地水准面和参考椭球面之间的差距(有时称为大地水准面差距)。它可以是正负。负的大地水准面差距说明大地水准面在参考椭球面之下,正的大地水准面差距说明大地水准面在参考椭球面之上。大地高(h)是高于或低于椭球的距离(正负)。大地高也被称为大地的高度。2.2Mapprojection地图投影2.2.1Definitionofmapprojection地图投影的定义MapprojectionsareattemptstoportraythesurfaceoftheEarthoraportionoftheEarthonaflatsurface.Somedistortionsofconformality,distance,direction,scale,andareaalwaysresultfromtheprocessofmapprojection.Someprojectionsminimizedistortionsinsomeofthesepropertiesatexpenseofmaximizingerrorsinothers.Sonoprojectioncanbesimultaneouslyconformalandarea-preserving.地图投影是试图描述地球的外表或地球的一局部放在平面上时的形状。一些变形的保形性、距离、方向、比例尺、区域总是源于地图投影的过程。一些投影减少局部特性的变形以增大其他地区的误差为代价。所以没有一种变形能同时具有保形性和保区域性。2.2.2Distortionsofmapprojection地图投影变形Conformality:Whenthescaleofamapatanypointonthemapisthesameinanydirection,theprojectionisconformal.Meridians(linesoflongitude)andparallels(linesoflatitude)intersectatrightangles.Shapeispreservedlocallyonconformalmaps.保形性:当地图上任意一点儿地图比例尺在任何时候在任何方向都是相同的,这种投影就是正形投影。子午线(经度线)和平行线(纬度)相交成直角。形状在映射地图中被保存为原形。Distance:Amapisequidistantwhenitportraysdistancesfromthecenterofprojectiontoanyotherplaceonthemap.距离:地图上任何一点到投影中心的距离是的等距的。Equidistantprojection,akindofarbitraryprojection,isreferredtothatthedistanceremainsconstantafterprojectedalongaspecificdirection,namelyalongthespecificdirection,thelengthratioisequalto1.Inthepracticalapplications,themeridiansareusuallyprojectedasstraightlines,andthedistancesalongalongitudinaldirectionaremaintainedequal,theanglesandareasaredistorted.Theequidistantprojectionisfrequentlyusedfordrawingtrafficmap.等距投影,一种任意投影,被称为投影后沿特定的方向距离保持不变,即沿特定的方向,长度比率等于1。在实际应用程序中,子午线通常投影为直线,并沿经线方向保持相等的距离,角度和区域发生变形。等距投影经常用于绘制交通地图。Direction:Amappreservesdirectionwhenazimuths(anglesfromapointonalinetoanotherpoint)areportrayedcorrectlyinalldirections.Scale:Scaleistherelationshipbetweenadistanceportrayedonamapandthesamedistanceontheearth.Area:whenamapportraysareasovertheentiremapsothat