Unit 2 Geodetic Surveying and Plane Surveying

Unit2GeodeticSurveyingandPlaneSurveyingContentsSurveyingGeodeticsurveyingPlanesurveyingSurveyingThedefinitionSurveyinghasbeentraditionallydefinedastheartandscienceofdeterminingthepositionofnaturalandartificialfeatureson,aboveorbelowtheearth’ssurface;representingthisinformationinanalogformasacontouredmap,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。）Themajortask:Theaccuratedeterminationandmonumentation(标石，标志）ofpointsonthesurfaceoftheEarth,involvesmeasurementsandcomputationsor,basically,fieldworkandofficework.（因此精确确定并标定地表点位便成为测量的主要任务）Basicoperations:Thoughthesesurveysareforvariouspurposes,stillthebasicoperations（基本业务）arethesame---theyinvolvemeasurementsandcomputationsor,basically,fieldworkandofficework.（虽然测量工作有不同目的，基本的业务却都一样――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）Differenttypesofsurveys:landsurveys,routesurveys,citysurveys,constructionsurveys,hydrographicsurveys,etc.土地测量，路线测量，城市测量，建筑测量，水道测量等等Twomajorcategories:geodeticsurveyingandplanesurveying大地测量和平面测量Howtodistinguish:geodeticsurveying:takesthetrueshapeoftheearthintoaccount考虑地球真实形状planesurveyingtreatstheearthasaflatsurface将地球当成一个平面AdditionaltypesofsurveyingHorizontalsurveys水平测量:surveysareconductedforthepurposeofpositioningfeaturesontheground.确定平面位置的水平测量Verticalsurveys高程测量:surveysareconductedforthepurposeofdeterminingtheelevationorheightsoffeatures.确定海拔的高程测量GeodeticSurveyingThedefinitionThetypeofsurveyingthattakesintoaccountthetrueshapeoftheearthiscalledgeodeticsurveying.（考虑地球真实形状的测量工作称为大地测量）Understandingofgeodeticsurveying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。）Methodsofgeodeticsurveying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）InstrumentsofgeodeticsurveyingInthepastground-basedtheodolites,tapes,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。）Thecomputationofdistancesingeodeticsurveys1.thetrueshapeoftheearthIngeodeticsurveys,theshapeoftheearthisthoughtofasaspheroid,althoughinatechnicalsense,itisnotreallyaspheroid.Therefore,distancesmeasuredonornearthesurfaceoftheeartharenotalongstraightlinesorplanes,butonacurvedsurface.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。）（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。)2.AllowancesHence,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。）3.ExpressionofthepositionsThepositionsareexpressedaslatitudes(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。）ThesignificanceofgeodeticsurveyAgeodeticsurveyestablishesthefundamentalsforthedeterminationofthesurfaceandgravityfieldofacountry.（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）PlaneSurveyingThedefinitionThetypeofsurveyinginwhichthemeansurfaceoftheearthisconsideredaplane,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]）Understandingofplanesurveying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，所有的角被认为都是平面角。）ComputationsinplanesurveyingTomakecomputationsinplanesurveying,youwilluseformulasofplanetrigonometry,algebra,andanalyticalgeometry.（在平面测量的计算中，你可以使用平面三角、代数、和平面解析几何的公式）Forsmallareas,preciseresultsmaybeobtainedwithplanesurveyingmethods,buttheaccuracyandprecisionofsuchresultswilldecreaseastheareasurveyedincreasesinsize.（小范围内，平面测量方法可以获