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时间:2019-11-24
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1、Unit5Traversing(导线测量)Thepurposeofthesurveyingistolocatethepositionsofpointsonornearthesurfaceoftheearth.(测量的目的是确定地表或接近地表的点的点位。)Todeterminehorizontaipositionsofarbitrarypointsonlheearth"ssurfaceandelevationofpointsaboveorbelowarefereneesurfaceareknownasacontrolsurvey.(确定地表任一[arbitrar
2、y任意的]点的平血位置和确定点高于或低于个参考血的高程的工作被称为控制测量)Thepositionsandelevationsofthepointsmakeupacontrolnetwork.(这些点的平面位置和高程组成了一个控制网)Therearediffcrcnttypesofcontrolnetworksdopendingonwhereandwhytheyareestab1ished・(依照它们建立的地点和口的不同,有不同的控制网类型)Acontrolnetworkmayhaveveryaccuratepositionsbutnoelevations(c
3、alledaHorizontalControlNetwork)orveryaccurateelevationsbutnopositions(calledaVerticalControlNetwork).(—个控制网可能有精确的平面位置而没有高程(称为平而控制网),或者有精确的高程而没有平而位置(称为高程控制网))Somepointsinaconirolnelworkhavebothaccuratepositionsandelevations.(有制网的点既有精确的平面位置也冇精确的高程)Controlnetworksrangefromsmall,simplea
4、ndinexpensivetolargeandcomplexandveryexpensivetoestablish.(控制网的范
5、韦
6、从小的、简单的、便宜的网到人的、复杂的、昂贵的网)Acontrolnetworkmaycoverasma11areabyusinga"local”coordinatesystemthatallowsyoutopositionthefeaturesinrelationtothecontrolnetworkbutdoesn"ttellyouwherethefeaturesareonthesurfaceoftheearth,orcov
7、eralargeareabyconsistin£ofafewwel1-placedandprecise-establishedcontrolpoints,whichissometimescalledtheprimarycontrol.(—个控制网町以是覆盖小范围,使用区域处标系统,允许你相对于控制网确定地貌特征【fcatum】,但却不告诉你它们在地表的什么地方;或者覆盖一个广人区域,由少数被适当女置并精确测设的控制点组成,冇时被称为基础控制)Thehorizontalpositionsofpointsinanetworkcanbeobtainedinanumb
8、erofdifferentways.(控制网的点的平面位置可以由许多不同方法來获得)Thegenerallyusedmethodsaretriangulation,trilateration,traversing,intersection,resectionandGPS.(—般使用的方法有,三角测用、三边测用、导线测址、交会测址、示方交会测量、和GPS测虽)Themaintopicofthistextreferstothetraversing.(这篇课文主要讲的是导线测量)Triangulation(三角测量)Themethodofsurveyingcalle
9、dtriangulationisbasedonthetrigonometricpropositionthatifonesideandthreeanglesofatriangleareknown,theremainingsidescanbecomputedbythelawofsines・(这乖中测量方法称为~^用测量,荒于=角【trigonomolricr角法的】法则【proposition命题】,【that弓I导的宾语从句】如果厂角形的•条边和厂个角已知,剩下的边可以用匸弦定理【law(江sines】计算出)Furthermore,ifthedirection
10、ofonesideisknown,th
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