Unit 5 Traversing

Unit5TraversingIBasicterms•controlsurvey•controlnetworkIITriangulationIIITrilaterationIVTraversingControlsurveyandcontrolnetworkThepurposeofthesurveyingistolocatethepositionsofpointsonornearthesurfaceoftheearth.（测量的目的是确定地表或接近地表的点的点位。）Acontrolsurveyistodeterminehorizontalpositionsofarbitrarypointsontheearth’ssurfaceandelevationofpointsaboveorbelowareferencesurface.（确定地表任一【arbitrary任意的】点的平面位置和确定点高于或低于一个参考面的高程的工作被称为控制测量）ControlnetworkThepositionsandelevationsofthepointsmakeupacontrolnetwork.（这些点的平面位置和高程组成了一个控制网）DifferenttypesofcontrolnetworksThesetypesdependonwhereandwhytheyareestablished.a)HorizontalControlNetwork:Acontrolnetworkmayhaveveryaccuratepositionsbutnoelevations.（一个控制网可能有精确的平面位置而没有高程（称为平面控制网）b)VerticalControlNetwork:Acontrolnetworkmayhaveveryaccurateelevationsbutnopositions.有精确的高程而没有平面位置（称为高程控制网））c)Thethirdtype:Somepointsinacontrolnetworkhavebothaccuratepositionsandelevations.（有些控制网的点既有精确的平面位置也有精确的高程）TherangeofcontrolnetworksControlnetworksrangefromsmall,simpleandinexpensivetolargeandcomplexandveryexpensivetoestablish.（控制网的范围从小的、简单的、便宜的网到大的、复杂的、昂贵的网）SmallareaandlargeareaAcontrolnetworkmaycoverasmallareabyusinga“local”coordinatesystemthatallowsyoutopositionthefeaturesinrelationtothecontrolnetworkbutdoesn’ttellyouwherethefeaturesareonthesurfaceoftheearth,orcoveralargeareabyconsistingofafewwell-placedandprecise-establishedcontrolpoints,whichissometimescalledtheprimarycontrol.（一个控制网可以是覆盖小范围，使用区域坐标系统，允许你相对于控制网确定地貌特征【feature】，但却不告诉你它们在地表的什么地方；或者覆盖一个广大区域，由少数被适当安置并精确测设的控制点组成，有时被称为基础控制）ThegenerallyusedmethodsofcontrolsurveyTriangulation三角测量Trilateration三边测量Traversing导线测量Intersection交会测量resection后方交会测量GPS.Themaintopicofthistextreferstothetraversing.TriangulationThemethodofsurveyingcalledtriangulationisbasedonthetrigonometricpropositionthat这种测量方法称为三角测量，基于三角【trigonometric三角法的】法则【proposition命题】，（【that引导的定语从句】1)ifonesideandthreeanglesofatriangleareknown,theremainingsidescanbecomputedbythelawofsines.如果三角形的一条边和三个角已知，剩下的边可以用正弦定理【lawofsines】计算出）2)ifthedirectionofonesideisknown,thedirectionoftheremainingsidescanbedetermined.（而且，如果一条边的方向已知，余下的边的方向也可以确定）3)Andthencoordinatesofunknownpointscanbecomputedbyapplicationoftrigonometry.（那么未知点的坐标就可以使用三角法计算出来）TrilaterationThetrilaterationisbasedonthetrigonometricpropositionthat（三边测量基于三角法则）ifthethreesidesofatriangleareknown,thethreeanglescanbecomputedbythelawofcosines.——如果三角形的三条边已知，那么三个角可以由余弦定理【lawofcosines】计算出）TheuseoftrilaterationTrilaterationwasadoptedtocombinewithtriangulationsincetheadventoflong-rangeEDMinstrument.（自从远距EDM出现【advent出现】以来，一种叫做三边测量的方法用来和三角测量联合使用。）TrilaterationpossessessomeadvantagesovertriangulationbecausethemeasurementofthedistanceswithEDMinstrumentissoquick,preciseandeconomical.（三边测量具有【possess拥有、具有】一些相对于三角测量的优势，EDM测距快速、准确、经济，而三角测量所需的角度测量则相对困难和昂贵）Triangulateration边角测量Forsomepreciseprojects,thecombinationoftriangulationandtrilaterationisapplied.在一些精密工程当中，三角测量和三边测量联合使用，被称为边角测量）TraversingDefinitionAsurveytraverseisasequenceoflengthsanddirectionsoflinesbetweenpointsontheearth,obtainedbyorfromfieldangleanddistancemeasurementsandusedindeterminingpositionsofthepoints.（【测量工作中的】导线是一系列【sequence次序、系列】地球上点之间的有长度和方向的直线，【导线】由野外角度和距离测量获得，用来确定点位）ThemeasurementoftraverseTheanglesaremeasuredByusingtransits,theodolites,ortotalstations.ThedistancescanbemeasuredByusingsteeltapesorEDMinstruments.Asurveytraversemaydeterminetherelativepositionsofthepointsthatitconnectsinseries,andiftiedtocontrolstationsbasedonsomecoordinatesystem,thepositionsmaybereferredtothatsystem.（导线可以用来确定互相连接点的相对位置【relativeposition】，如果想控制某些坐标系中的站点【以某坐标系的点为站点】，其【指stations】位置应参考该坐标系）Fromthesecomputedrelativepositions,additionaldatacanbemeasuredforlayoutofnewfeatures,suchasbuildingsandroads.（从这些计算出的相对位置，另外的数据可以量出来，用以放样【layout】新的地物【features特征，理解为地物】，如：建筑物和道路。）ThefunctionoftraversingSincetheadventofEDMequipment,traversinghasemergedasthemostpopularmethodtoestablishcontrolnetworkssuchasbasicareacontrol,mapping,controlofhydrographicsurveysandconstructionprojects.（自从EDM的出现【advent】，导线测量作为最常用的建立控制网的方法显现【emerge显现】出来，例如基础区域控制、图根控制、水道测量控制和建筑工程控制【建筑施工控制】）Inengineeringsurveying,itisidealwaytosurveysanddimensionalcontrolofroute-typeprojectssuchashighway,railroad,andpipelineconstruction.（在工程测量当中，导线测量是线型工程测量和立体【dimensional空间的】控制的理想方法，线型工程例如公路、铁路、和管线建筑）TheclassificationoftraverseIngeneral,atraverseisalwaysclassifiedaseitheranopentraverseoraclosedtraverse.（总体上【Ingeneral】，导线总是分为支导线和闭路导线【按说opentraverse是支导线，closedtraverse是闭合导线，而connectingtraverse是附合导线】）OpentraverseAnopentraverseoriginateseitheratapointofknownhorizontalpositionwithrespecttoahorizontaldatumoratanassumedhorizontalposition,andterminatesatastationwhoserelativepositionisnotpreviouslyknown.（支导线起始于【originate起源】一个水平位置已知（相对于一个水平基准【水平坐标系】）或水平位置假定的点，终止【terminate】于相对位置【relativeposition】事先未知的站点。）FeaturesofopentraverseTheopentraverseprovidesnocheckagainstmistakesandlargeerrorsforitsterminationatanunknownhorizontalpositionandlackofgeometricclosure.（由于其终点位置未知并且缺乏图形闭合【geometric几何的】【closure闭合n.】，支导线不能提供对错误和较大误差的检核）Thislackofgeometricclosuremeansthattherei