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Aworkingdefinitionmightbe“theart,scienceandtechnologiesrelatedtothemanagementofgeographically-referencedinformation.”现行的一个定义是“涉及工艺、科学和技术的地理信息的处理”Surveyinghasbeentraditionallydefinedastheartandscienceofdeterminingthepositionofnaturalandartificialfeatureson,aboveorbelowtheearthssurface;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；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）Thetermisusedtodesignatesurveyworkinwhichthedistancesorareasinvolvedareoflimitedextent.（这个术语曾指涉及的距离及范围非常有限的测量工作）Withregardtohorizontaldistancesanddirections,alevellineisconsideredmathematicallystraight,thedirectionoftheplumblineisconsideredtobethesameatallpointswithinthelimitsofthesurvey,and allanglesareconsideredtobeplaneangles.（由于被当成了水平距离和方向，水平线被当成直线，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。）Thereisclosecooperationbetweengeodeticsurveyingandplanesurveying.（大地测量和平面测量关系密切。）Thegeodeticsurveyadoptstheparametersdeterminedbymeasurementsoftheearth,anditsownresultsareavailabletothosewhomeasuretheearth.（大地测量采用通过测量地球得到的参数，而其计算结果又可以被测量地球的工作所利用）Theplanesurveys,inturn,aregenerallytiedtothecontrolpointsofthegeodeticsurveysandserveparticularlyinthedevelopmentofnationalmapseriesandintheformationofrealestatecadastres.（接下来，平面测量，一般依赖于大地测量建立的控制点，在国家地图系列的发展和在房地产地籍信息领域提供特别服务。）Horizontalandslopedistancescanbemeasuredwithlotsoftechniquesofmeasurementdependingonthedesiredqualityoftheresult.（根据测量结果的精度要求不同，平距或斜距有多种测量方法）Ahorizontallineatapointisanylinethatisperpendiculartotheverticallineatthepoint.（一点上的水平线是垂直于过该点的垂线的直线。）Withthetheodolitesetup,centered,andleveledoveratstationA,thenasimplehorizontalanglemeasurementbetweensurveyingpointB,AandCwouldbetakenasfollows:（经纬仪在A点安置、对中、整平后，在B、A和C测量点间的简单的水平角测量可以按下列步骤进行：）Commencingon,say,“faceleft”,thetargetsetatsurveypointBiscarefullybisectedandthereadingonhorizontalscaleis25.（着手，说“盘左”将B点的目标仔细分中，水平，度盘读数为25度）TheupperplateclampisreleasedandtelescopeisturnedclockwisetosurveypointC.Thereadingonhorizontalcircleis75（水平度盘制动螺旋松开，顺时针转动望远镜至C点，水平度盘读数75度）Thehorizontalangleisthenthedifferenceofthetwodirections,i.e.(75-25)=50（水平角就是两个方向值的差值，即，(75-25)=50）ChangefaceandobservepointCon“faceright”,andnotethereading=255（换度盘方向至盘右并照准C点，记下读数为255度）ReleaseupperplateandswingcounterclockwisetopointBandnotethereading=205（松开水平度盘，逆时针旋转至B点并记下读数为205度）Thereadingorthedirectionmustbesubtractedinthesameorderas255-205=50（读数或者说是方向值按同样的法则相减，255-205=50）Themeanoftwovalueswouldbeacceptediftheyareinacceptableagreement.（如果两个减出来的值的一致性是可接受的，取两个值的平均值。）Azimuthisthehorizontalanglemeasuredinaclockwisedirectionfromtheplaneofthemeridian,whichisalineonthemeansurfaceoftheearthjoiningthenorthandsouthpoles.（方位角是从子午面起算按顺时针旋转的角，子午线是在地球平均表面连接北极与南极的线）Azimuthrangesinmagnitudefrom0to360,valuesinexcessof360,whicharesometimesencounteredincomputations,aresimplyreducedby360beforefinallisting.（方位角的取值范围从0度到360度，超过360的值有时会在计算时遇到，只需减去360度即可）Thetotalerrorofangularclosureshouldbedistributedevenlytoeachangle(ifallanglesweremeasuredwiththesameprecision)beforemathematicalanalysisofthetraverse.（在导线进行数学分析之前，角度闭合差应该平均分配到每个角上（如果所有的角都是相同观测精度）Closedtraversesprovidealsochecksonthemeasureddistances,andthepositionclosurecanbedeterminedmathematically,whichmeansthatanindicationoftheconsistencyofmeasuringdistancesaswellasanglesshouldbegiventoatraversethatclosesonitself.（闭合导线同时提供测量过的距离的检核，位置的闭合差可以计算得到，这就意味着测量的距离同测角一样，应当予以闭合。）Themodernapproachistomeasuretheslopedistanceandverticalangletothepointinquestion.（现代的三角高程测量方法是测量到未知点的斜距和垂直角）Slopedistanceismeasuredusingelectromagneticdistancemeasurersandthevertical(orzenith)angleusingatheodolite,orthetotalstationthatintegratethesetwoinstrumentsintoasingleinstrument.（斜距由电磁波测距仪测得，垂直角（或天顶距）由经纬仪测得，或者利用整合了这两种仪器为一体的全站仪来测）Totalstationscontainbuilt-inmicroprocessorsthatcalculateanddisplaythehorizontaldistancefromthemeasuredslopedistanceandverticalheight.（全站仪包含了内置的微处理器，用来根据测得的斜距和垂直角计算和显示水平距离）Thislatterfacilityhasresultedintrigonometricallevelingbeingusedforawidevarietyofheightingprocedures,includingcontouring.（这种后来的设备导致了三角高程测量被广泛用于多种高度测量工作，包括测绘等高线ThebasicconceptoftrigonometricallevelingcanbeseenfromFigure2.（三角高程测量的基本原理可以看图2）WhenmeasuringtheverticalangleandthehorizontaldistanceSisused,thenthedifferenceinelevationhABbetweengroundpointsAandBistherefore:（当我们用和S分别表示垂直角和水平距离时，A点和B点之间的高差为：）Itcanbestatedunconditionallythatallmeasurements,nomatterhowcarefullyexecuted,willcontainerror,andsothetruevalueofameasurementisneverknown,andtheexactsizesoftheerrorspresentarealwaysunknown.（可以绝对地【unconditionally无条件地】说【state声明】，所有测量工作，无论多么仔细的实行【execute】，也会包含误差，因此测量的真值是永远不知道的，出现【present出现】的确切的【exact】误差大小也永远不知道）Evenwiththemostsophisticatedequipment,ameasurementisonlyanestimateofthetruesizeofaquantity.（即使使用最复杂精密的装置，测量值也仅仅是一个量的真值的估计【estimate】）Thisisbecausetheinstruments,aswellasthepeopleusingthemareimperfect,becausetheenvironmentinwhichtheinstrumentsandpeopleoperateinfluencestheprocess,andbecausethebehaviorofpeople,instruments,andtheenvironmentcannotbefullypredicted.（这是因为同使用它们的人一样，仪器是不完美的【imperfect】，因为仪器和人的操作环境影响观测过程，因为人的行为，仪器，和环境不能完全预知【predicte】）However,measurementscanapproachtheirtruevaluesmorecloselyasbetterequipmentisdeveloped,environmentalconditionsimproveandobserverabilityincreases,buttheycanneverbeexact.（然而，测量可以非常接近它们的真值，当【as】仪器的改进，环境条件改善和观测者技术【ability】的进步时。但是它们永远不能达到真值）Bydefinition,anerroristhedifferencebetweenameasuredvalueforanyquantityanditstruevalue.（按照【By】定义，误差是某一量的测量值和它的真值之间的差值。）Thesourcesoferrorsfallintothreebroadcategorieswhicharedescribedasfollows:（误差来源分成【fallinto分成、属于、落入】三个主要的【broad】类型【category】，描述如下：）Exampl