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Unit2GeodeticSurveyingandPlaneSurveying（大地测量与平面测量）Surveyinghasbeentraditionallydefinedastheartandscienceofdeterminingthepositionofnaturalandartificialfeatureson,aboveorbelowtheearth’ssurface;andrepresentingthisinformationinanalogformasacontouredmap,paperplanorchart,orasfiguresinreporttables,orindigitalformasathreedimensionalmathematicalmodelstoredinthecomputer.（测量传统定义为确定地表、地下和地上的自然与人工地貌特征【features形态、特征】；并使之按比例【inanalogform】测绘成地形图【contouredmap】、平面图【paperplan】或图表，或形成报告图表，或以数字形式形成三维立体数学模型存储进计算机。）Assuch,thesurveyor/geodesistdealtwiththephysicalandmathematicalaspectofmeasurement.（同样的，测量员/大地测量学家处理的就是测量出的物理的和数学的特征）Theaccuratedeterminationandmonumentation【标石、标志】ofpointsonthesurfaceoftheEarthisthereforeseenasthemajortask.（因此精确确定并标定地表点位便成为测量的主要任务）Thoughthesesurveysareforvariouspurposes,stillthebasicoperationsarethesame---theyinvolvemeasurementsandcomputationsor,basically,fieldworkandofficework.（虽然测量工作有不同目的，基本的操作却都一样――他们包括测量和计算，或更基本地称之为，外业工作和内业工作）Therearemanydifferenttypesofsurveyssuchaslandsurveys,routesurveys,citysurveys,constructionsurveys,hydrographicsurveys,etc.,butgenerallyspeaking,surveyingisdividedintotwomajorcategories:geodeticandplanesurveying.（测量分为许多不同的类型，如土地测量，路线测量，城市测量，建筑测量，水道测量等等，但是总的来说，测量分为两个主要的种类：大地测量和平面测量）SurveyswilleithertakeintoaccountthetrueshapeoftheEarth（Geodeticsurveys）ortreattheearthasaflatsurface(Planesurveys).（是考虑地球真实形状的大地测量还是将地球当成一个平面的平面测量【紧跟着上句】）Additionally,surveysareconducted【表现】forthepurposeofpositioningfeaturesontheground(Horizontalsurveys),determiningtheelevationorheightsoffeatures(Verticalsurveys)oracombinationofboth.（另外，测量还分为确定平面位置的水平测量和确定海拔的高程测量或两者的综合。）GeodeticSurveying（大地测量）Thetypeofsurveyingthattakesintoaccountthetrueshapeoftheearthiscalledgeodeticsurveying.（考虑地球真实形状的测量工作称为大地测量）Thistypeofsurveyissuitedforlargeareasandlonglinesandisusedtofindthepreciselocationofbasicpointsneededforestablishingcontrolforothersurveys.（这种测量适用于大范围和长距离的测量工作，用来确立基本点的精确位置，用以建立其他测量工作所需的控制网。）Ingeodeticsurveys,thestationsarenormallylongdistancesapart,andmorepreciseinstrumentsandsurveyingmethodsarerequiredforthistypeofsurveyingthanforplanesurveying.（在大地测量中，站点经常是互相距离很远，那么这种测量就比平面测量需要更精确的仪器和测量方法。）Widelyspaced,permanentmonumentsserveasthebasisforcomputinglengthsanddistancesbetweenrelativepositions.（广泛间隔开的永久标石就作为计算点位之间距离的基础）【serve当作】Thesebasicpointswithpermanentmonumentsarecalledgeodeticcontrolsurveypoints,whichsupporttheproductionofconsistentandcompatibledataforsurveyingandmappingprojects.（这种永久标石点被称为大地控制点，为测量和绘图工作提供可靠和一致的数据）Inthepast,ground-basedtheodolites,tapes【卷尺】,andelectronicdevicesweretheprimarygeodeticfieldmeasurementsused.（过去，大地经纬仪【DJ大地经纬仪的中文缩写】、卷尺和电子设备是大地测量的野外工作初时【primary】的工具。）Today,thetechnologicalexpansionofGPShasmadeitpossibletoperformextremelyaccurategeodeticsurveysatafractionofthecost.（现在，GPS技术的发展【expansion扩充、膨胀】使大地测量工作花费非常小的代价【afractionof一小部分】就能获得极为精确的结果成为可能。）Athoroughknowledgeoftheprinciplesofgeodesyisanabsoluteprerequisitefortheproperplanningandexecutionofgeodeticsurveys.（大地测量工作计划的编制【planning】和实施【execution】，【proper恰当的，翻译时略掉】，绝对需要【absoluteprerequisite】对大地测量学知识有全面的掌握。【Athoroughknowledgeoftheprinciplesofgeodesyisanabsoluteprerequisite一个彻底的知识――大地测量学的原理的，是绝对需要的。】）InGeodeticSurveys,theshapeoftheearthisthoughtofasaspheroid,althoughinatechnicalsense,itisnotreallyaspheroid.（在大地测量中，地球的形状被看成一个椭球体，虽然在技术角度来看，它不是真正的椭球。）Therefore,distancesmeasuredonornearthesurfaceoftheeartharenotalongstraightlinesorplanes,butonacurvedsurface.（因此，在地球表面上或附近测量距离并不是沿着直线或平面进行，而是在一个曲面上。)Hence,inthecomputationofdistancesingeodeticsurveys,allowancesaremadefortheearth’sminorandmajordiametersfromwhichaspheroidofreferenceisdeveloped.（因此，在大地测量距离的计算中，参考椭球的长轴与短轴所带来的误差就显示【develop显示出来】出来。）Thepositionofeachgeodeticstationisrelatedtothisspheroid.（每个大地站点的位置都与这个椭球有关）Thepositionsareexpressedaslatitudes(anglesnorthorsouthoftheEquator)andlongitudes(angleseastorwestofaprimemeridian)orasnorthingsandeastingsonarectangulargrid.（这个位置是用纬度（与赤道面所成的角）和经度（与初子午线所成的角）或用在直角坐标系中的北距和东距来表示。）Ageodeticsurveyestablishesthefundamentalsforthedeterminationofthesurfaceandgravityfieldofacountry.（大地测量为建立国家范围内的重力场和确定地表架构提供【establishes建立】基础）Thisisrealizedbycoordinatesandgravityvaluesofasufficientlylargenumberofcontrolpoints,arrangedingeodeticandgravimetricnetworks.（这将由测定布设在大地网和重力网中数量十分巨大的控制点，所得到的坐标和重力值来实现）Inthisfundamentalwork,curvatureandthegravityfieldoftheearthmustbeconsidered.（在这项基础工作中，地球的曲率和重力场都应被考虑。）PlaneSurveying（平面测量）Thetypeofsurveyinginwhichthemeansurfaceoftheearthisconsideredaplane,orinwhichthecurvatureoftheearthcanbedisregardedwithoutsignificanterror,generallyiscalledplanesurveying.（这种类型的测量把地球平均的表面视作平面，或认为地球曲率带来的误差可以忽略不计，这样的测量工作称为平面测量[significant重大的，不翻译也行]）Thetermisusedtodesignatesurveyworkinwhichthedistancesorareasinvolvedareoflimitedextent.（这个术语曾指涉及的距离及范围非常有限的测量工作【extent范围】）Withregardtohorizontaldistancesanddirections,alevellineisconsideredmathematicallystraight,thedirectionoftheplumblineisconsideredtobethesameatallpointswithinthelimitsofthesurvey,andallanglesareconsideredtobeplaneangles.（由于被当成了水平距离和方向，水平线被当成直线【省略掉mathematically】，在这个有限范围内所有点上的铅垂线方向被认为是相同的，所有的角被认