artificialfeatures on,aboveorbelowtheearth's surface,andrepresentingthis information inanalogfom asacontoured map, paper plan or chart or as figures in report tables, or in digital form as a three dimensionalmathematicalmodelstoredinthecomputer.（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/geodesistdealtwiththephysicalandmathematical aspectofmeasurement.（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）The accuratedetermination andmonumentation【标石、标志】ofpointsonthesurfaceoftheEarthistherefore seen as themajortask.（因此精确确定并标定地表点位便成为测量的主要任务）Thoughthesesurveys areforvariouspurposes,still the basic operations are the same---they involve measurements and computations or,basically,fieldworkandofficework（虽然测量工作有不同目的，基本的操作却都一样一一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）Therearemanydifferenttypes of surveys such as land surveys,route surveys, city surveys, construction surveys, hydrographic surveys, etc., but generally speakingsurveying isdivided into twomajor categories:geodetic andplane surveying.（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）Surveys will eithertake into accountthe true shape of the Earth（Geodetic surveys）ortreattheearthas a flatsurface(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】for the purpose of positioning features on the ground(Horizontal surveys), determining the elevation orheightsoffeatures(Vertical surveys）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。）Geodetic Surveying（大地测量）The type of surveying that takes into account thetrue shape ofthe earth is called geodetic surveying.（考虑地球真实形状的测量工作称为大地测量）Thistypeofsurveyissuitedforlargeareasandlonglinesandisused to find the precise location ofbasic points needed forestablishing controlfor other surveys.（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。In geodetic surveys, the stations are normally long distances apart, and more precise instruments andsurveyingmethods arerequiredforthistypeof surveyingthanforplane surveying.（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。）Widely spaced,permanentmonuments serve as thebasisfor computinglengths and distances between relative positions.(广16
16 artificial features on, above or below the earth’s surface; and representing this information in analog form as a contoured map, paper plan or chart, or as figures in report tables, or in digital form as a three dimensional mathematical model stored in the computer. （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【in analog form】测绘成 地形图【contoured map】 、 平面图【paper plan】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。 ） As such, the surveyor/geodesist dealt with the physical and mathematical aspect of measurement. （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） The accurate determination and monumentation【标石、标志】 of points on the surface of the Earth is therefore seen as the major task. （因 此精确确定并标定地表点位便 成为测量的主要任务） Though these surveys are for various purposes, still the basic operations are the same-they involve measurements and computations or, basically, fieldwork and office work. （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） There are many different types of surveys such as land surveys, route surveys, city surveys, construction surveys, hydrographic surveys, etc., but generally speaking, surveying is divided into two major categories: geodetic and plane surveying. （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） Surveys will either take into account the true shape of the Earth （Geodetic surveys） or treat the earth as a flat surface(Plane surveys). （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, surveys are conducted【表现】 for the purpose of positioning features on the ground(Horizontal surveys), determining the elevation or heights of features(Vertical surveys) or a combination of both.（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。 ） Geodetic Surveying（大地测量） The type of surveying that takes into account the true shape of the earth is called geodetic surveying. （考虑 地球真实形状的测量工作称为大地测量） This type of survey is suited for large areas and long lines and is used to find the precise location of basic points needed for establishing control for other surveys. （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。 ） In geodetic surveys, the stations are normally long distances apart, and more precise instruments and surveying methods are required for this type of surveying than for plane surveying.（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。 ） Widely spaced, permanent monuments serve as the basis for computing lengths and distances between relative positions. （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】Thesebasicpointswithpermanent monuments are called geodetic control survey points, which support the production of consistentandcompatibledataforsurveyingandmappingprojects.（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】，and electronicdevicesweretheprimarygeodeticfieldmeasurementsused.（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,thetechnologicalexpansion of GPS has made it possible to perform extremely accurate geodetic surveys at a fraction of thecost.（现在，技术的发展GPS【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。）Athoroughknowledgeoftheprinciplesofgeodesyis an absolute prerequisitefor the proper planning and execution of geodetic surveys.（大地测量工作计划的编制【planning】和实施【executionproper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。thoroughknowledgeoftheprinciples【Aofgeodesyisanabsoluteprerequisite一个彻底的知识一一大地测量学的原理的，是绝对需要的。）】InGeodetic Surveys,theshape of the earth is thought of as a spheroid,although ina technical sense, it is notreallya spheroid.（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,distances measured on or nearthe surface ofthe earth are not along straight lines or planes, but on a curvedsurface.（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。）Hencein the computation of distances in geodetic surveys, allowances are made for the earth's minor and majordiametersfromwhicha spheroidofreferenceisdeveloped（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(angles north or south of the Equator) and longitudes(angles east or west of a prime meridian) or asnorthingsand eastings onarectangulargrid.（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。）Ageodeticsurveyestablishesthefundamentalsforthedeterminationofthesurfaceandgravityfieldofa country：（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】Thisisrealizedbycoordinates andgravityvalues of a sufficiently large number of control points, arranged in geodetic and gravimetric networks.(i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。）17
17 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】 These basic points with permanent monuments are called geodetic control survey points, which support the production of consistent and compatible data for surveying and mapping projects.（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） In the past, ground-based theodolites, tapes【卷尺】, and electronic devices were the primary geodetic field measurements used. （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, the technological expansion of GPS has made it possible to perform extremely accurate geodetic surveys at a fraction of the cost. （现在， 技术的发展 GPS 【expansion 扩充、膨胀】使大地测量工作花费非常小的代价【a fraction of 一小部分】就能获得极为 精确的结果成为可能。）A thorough knowledge of the principles of geodesy is an absolute prerequisite for the proper planning and execution of geodetic surveys.（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【absolute prerequisite】 对大地测量学知识有全面的掌握。 thorough knowledge of the principles 【A of geodesy is an absolute prerequisite 一个彻底的知识――大地测量学的原理的，是 绝对需要的。） 】 In Geodetic Surveys, the shape of the earth is thought of as a spheroid, although in a technical sense, it is not really a spheroid. （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, distances measured on or near the surface of the earth are not along straight lines or planes, but on a curved surface.（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, in the computation of distances in geodetic surveys, allowances are made for the earth’s minor and major diameters from which a spheroid of reference is developed. （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。 ） The position of each geodetic station is related to this spheroid. （每个大地站 点的位置都与这个椭球有关） The positions are expressed as latitudes(angles north or south of the Equator) and longitudes(angles east or west of a prime meridian) or as northings and eastings on a rectangular grid.（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。 ） A geodetic survey establishes the fundamentals for the determination of the surface and gravity field of a country. （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） This is realized by coordinates and gravity values of a sufficiently large number of control points, arranged in geodetic and gravimetric networks.（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） In this fundamental work, curvature and the gravity field of the earth must be considered.（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）The type of surveying in which the mean surface of the earth is considered a plane, or in which the curvatureof the earth can be disregarded without significant error,generally is called plane surveying.（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]】Thetermisusedtodesignate surveyworkinwhichthedistancesorareasinvolvedareof limited extent.（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】）With regard to horizontal distances and directions, a level line is considered mathematically straight.the direction of the plumb line is considered tobe the same at all points within the limits of the survey,and allanglesareconsideredtobeplaneangles.（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。）Tomakecomputations inplanesurveying,youwillusefomulasofplanetrigonometry,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）Forsmall areas,preciseresultsmaybeobtainedwithplanesurveyingmethods,butthe accuracy and precision of such results will decrease as the area surveyed increases in size.（小范围内，平面测量方法可以获得精确的结果，但是随着范围的扩大，精度和准确度将随之下降）Forexample,thelength of an arc18.5km long lying in the earth's surface is only7mm greater than the subtended chordand, further, the difference between the sum of the angles in a plane triangle and the sum of those in aspherical triangle is2only 0.51 second fora triangle at the earth's surface having an areaof100km.（例如，地球表面一条18.5km长的弧只比其所对的【subtend与....相对】弦长7mm，further【进一步，可以省略】，在一个面积为100平方公里的平面三角形中的内角和与对应球面三角形中的内角和之差只有0.51秒）Itwillbe appreciated that thecurvature of theearthmustbetaken into considerationonlyinprecisesurveysof largeareas.（只有在大面积的精密测量工作中地球曲率才必需被考虑【appreciated重视）Agreatnumberofsurveysareoftheplanesurveyingtype.（多数的测量工作都是属于平面测量类型）Surveysforthelocation and construction ofhighways,railroads,canals,and in general, the surveysnecessary for the works of human beings are plane surveys, as are the surveys made to establish boundaries.exceptstateandnational．（【特定】区域测量、公路【highway是干道的意思，speedway、freeway才是高速公路】建设、铁路、沟渠等，总的来说与人们工作密切相关的测量工作都是平面测量，不包括州界和国界测量在内的边界测量也同属平面测量）However，withtheincreasing sizeandsophistication of engineering and other scientific projects, surveyors who restrict their practice to planesurveying areseverelylimited inthetypesof surveys inwhichtheycanbeengaged.（然而，随着工程和其18
18 Plane Surveying（平面测量） The type of surveying in which the mean surface of the earth is considered a plane, or in which the curvature of the earth can be disregarded without significant error, generally is called plane surveying.（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]） The term is used to designate survey work in which the distances or areas involved are of limited extent.（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】 ） With regard to horizontal distances and directions, a level line is considered mathematically straight, the direction of the plumb line is considered to be the same at all points within the limits of the survey, and all angles are considered to be plane angles.（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。 ） To make computations in plane surveying, you will use formulas of plane trigonometry, algebra, and analytical geometry. （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） For small areas, precise results may be obtained with plane surveying methods, but the accuracy and precision of such results will decrease as the area surveyed increases in size. （小范围内， 平面测量方法可以获得精确的结果，但是随着范围的扩 大，精度和准确度将随之下降） For example, the length of an arc 18.5 km long lying in the earth’s surface is only 7mm greater than the subtended chord and, further, the difference between the sum of the angles in a plane triangle and the sum of those in a spherical triangle is 2 only 0.51 second for a triangle at the earth’s surface having an area of 100km . （例如， 地球表面一条 18.5km 长的弧只比其所对的 【subtend 与.相对】 弦长 7mm，further 【 进一步， 可以省略】 ，在一个面积为 100 平方公里的平面三角形中的内角和与对应球面三角 形中的内角和之 差只有 0.51 秒） It will be appreciated that the curvature of the earth must be taken into consideration only in precise surveys of large areas.（只有在大面积的精密测量工 作中地球曲率才必需被考虑【appreciated 重视】） 。 A great number of surveys are of the plane surveying type.（多数的测量工作都是属 于平面测 量类型） Surveys for the location and construction of highways, railroads, canals, and in general, the surveys necessary for the works of human beings are plane surveys, as are the surveys made to establish boundaries, except state and national. （ 【特定】 区域测量、公路【highway 是干道的意思，speedway、freeway 才 是高速公路】建设、铁路、 沟渠等， 总的来说与人们工作密切相关的测量工作都是平面测量， 不包 括州界和国界测量在 内的边界测量也同属平面测量） However, with the increasing size and sophistication of engineering and other scientific projects, surveyors who restrict their practice to plane surveying are severely limited in the types of surveys in which they can be engaged.（然而，随 着工程和其
他科学项目越来越大越来越复杂，在限定【restrict约束】于从事平面测量工作的测量员在他们可以从事的测量类型上受到严格【severely严格的】限制。【前面讲多数测量工作为平面测量，这里就转折的说从事平面测量的人员能进行的工作越来越少】）Theoperationofdeterminingelevationusuallyisconsideredadivisionof planesurveying。（我们通常把高程的测量与平面测量分开来。）Elevationsarereferredtothegeoid（高程参考的是大地水准面。【或者说高程是相对于大地水准面而言的】Thegeoid istheoretical only.（大地水准面只是在理论上存在）It isthenatural extensionofthemean sealevelsurfaceunderthelandmass.（它是平均海平面在大陆下的自然延伸。【它是平均海平面蔓延穿过大陆而成的】）Wecould illustratethis idea bydigginganimaginarytrenchacross thecountrylinkingtheAtlanticandPacificoceans.（我们可以通过挖掘一个的想象中的连通大西洋和太平洋沟渠【trench】来阐明【illustrate】这个概念。）Ifweallowedthetrenchtofillwithseawater,thesurfaceofthewaterinthetrenchwould representhegeoid．（如果我们允许这条沟渠注满海水，沟渠里的水面就代表大地水准面。）So for all intents and purposes, the geoid is the same as mean sea level.（因此，从所有的目的和用途出发，【直译：由于（为了？）所有的计划和目标】大地水准面与平均海平面是一样的。【fo引导原因】）Mean sea level istheaveragelevelof theocean surfacehalfwaybetweenthehighest andlowestlevelsrecorded.（平均海平面是海水表面高度的记录值的平均值。【直译：平均海平面是指海水面的最高和最低记录之间纪录值的平均值。）Weusemeansealevelasadatumor,curiouslyandincorrectly,a datum plane upon which we can reference or describe the heights of features on, above orbelowtheground.（我们用平均海平面作为一个数据，或不常用地和不准确地，当作一个基准面【datumplane】，通过它我们可以参考和描述地上、地表、地下的情况。）Imaginea trueplanetangentto the surfaceofmean sea level atagivenpoint（想象一个真正的平面与平均海平面在一个特定【given特定的、指定的】点上相切【tangent正切的、相切的】）。Athorizontaldistancesof1kmfromthepointof tangency, the vertical distances(or elevations) of the plane above the surface represented by mean sea levelare7.8cm.（在离切点1km的地方，这个平面高于平均海平面的垂直距离为7.8cm。【representby通过.....描述】）Obviously,curvatureof theearth's surface is afactor that cannotbeneglected in obtainingevenroughvaluesof elevations．（很明显，即使在获取粗略的高程值的时候，地球表面曲率也是一个不可忽略的因素。）Theordinaryprocedureindeterminingelevations,suchas【像这样、例如】balancingbacksight and foresight distancein differential leveling,automatically takes into account the curvature of theearth and compensates for earth curvature and refraction, and elevationsreferredto the curved surface ofreferencearesecuredwithoutextraeffortbythesurveyor（常规的测高程的程序是，例如，在微差水准测量【differentialleveling】中平衡前后视距【使前后视距相等】，地球曲率和大气折光影响将被自动考19
19 他科学项目越来越大越来越复杂，在限定【restrict 约束】于从事平面测量工 作的测量员在他们可以 从事的测量类型上受到严格【severely 严格的】限制。 【前面讲多数 测量工作为平面测量，这里就 转折的说从事平面测量的人员能进行的工作越来越少】）The operation of determining elevation usually is considered a division of plane surveying. （我们通常把高程的测量与平面测量分开来。 ） Elevations are referred to the geoid.（高程参考的是大地水准面。 【或者说高程是相对 于大地水准面而言的】 ） The geoid is theoretical only.（大地水准面只是在理论上存在） It is the natural extension of the mean sea level surface under the landmass. （它 是平均海平面在大陆下的自然延伸。 【它是平均海平面蔓延穿 过大陆而成的】 ） We could illustrate this idea by digging an imaginary trench across the country linking the Atlantic and Pacific oceans.（我们可以通过挖掘一个的想象中的连通大西 洋和太平洋沟渠【trench】 来阐明【illustrate】这个概念。 ） If we allowed the trench to fill with seawater, the surface of the water in the trench would represent he geoid. （如果我们允许这条沟渠注满海水，沟渠里的水面就代表大地 水 准面。 ） So for all intents and purposes, the geoid is the same as mean sea level. （因此， 从所有的目的 和用途出发， 【直译：由于（为了？）所有的计划和目标】大地水准面与平均 海平面是一样的。【for 引导原因】 ） Mean sea level is the average level of the ocean surface halfway between the highest and lowest levels recorded. （平均海平面是海水表面高度的记录值的平均值。 【直译： 平均海平面是指 海水面的最高和最低记录之间纪录值的平均值。） 】 We use mean sea level as a datum or, curiously and incorrectly, a datum plane upon which we can reference or describe the heights of features on, above or below the ground.（我们用平均海平面作为一个数据， 或不常用地和不准确地， 当作一个基准面 【datum plane】 ，通过它我们可以参考和描述地上、地表、地下的情况。 ） Imagine a true plane tangent to the surface of mean sea level at a given point. （想 象一个真正的平面与平均海平面在一个特定【given 特定的、指定的】点上相切【tangent 正切的、相切的】） 。 At horizontal distances of 1km from the point of tangency, the vertical distances(or elevations) of the plane above the surface represented by mean sea level are 7.8cm. （在离切点 1km 的地方，这个平面高于平均海平面的垂直距离为 7.8cm。【represent by 通 过.描述】 ） Obviously, curvature of the earth’s surface is a factor that cannot be neglected in obtaining even rough values of elevations. （很明显，即使在获取粗略的高程值的 时候，地球表面曲率也是一个 不可忽略的因素。 ） The ordinary procedure in determining elevations, such as【像这样、例如】 balancing backsight and foresight distance in differential leveling, automatically takes into account the curvature of the earth and compensates for earth curvature and refraction, and elevations referred to the curved surface of reference are secured without extra effort by the surveyor.（常规的测高程的程序是，例如，在微差水准测 量【differential leveling】中平衡前后视距【使前后视距相等】 ，地球曲率和大气折光影响将被自动考
虑和低偿【compensate】，不必经测量者额外改正【effort努力】，至参考曲面的高程就是可靠的了。）There is close cooperationbetweengeodetic surveyingand planesurveying（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【确定地球参数】的工作所利用【available可利用的】）Theplanesurveys, in turn, are generally tied to the control points of the geodetic surveys and serve particularly in thedevelopmentofnationalmapseriesandintheformationofrealestatecadastres.（接下来【inturn】，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【国家地图集】的发展和在房地产地籍【realestatecadastre】信息领域提供特别服务。）课次序号：42 学时UnitFourDistanceMeasurement一、本单元的重点难点：1、主语从语These velocities, which are affected by the air's density, are reduced and need to berecalculated in the atmosphere2、强调比较级Ifthedistance is longerthan the length oftape, thenwe candividethelongdistanceintoseveral segmentsandgetthetotal distancebyplus each segmenttogether二、对学生的要求：1、必须掌握本单元的重点难点内容；2、复习pacing,precise ranging,distance measurement, bymeans of,a series of3、掌握专业词汇distancemeasuringinstrument,rangefinder@ geodimeter long-range EDM instrument20
20 虑和 低偿【compensate】 ，不必经测量者额外改正【effort 努力】 ，至参考曲面的高程就是可靠 的 了。 ） There is close cooperation between geodetic surveying and plane surveying.（大地 测量和平面测 量关系密切。）The geodetic survey adopts the parameters determined by measurements of the earth, and its own results are available to those who measure the earth. （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【确定地球参数】的工作所利用 【available 可利用的】 ） The plane surveys, in turn, are generally tied to the control points of the geodetic surveys and serve particularly in the development of national map series and in the formation of real estate cadastres.（接下来【in turn】 ，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【国家地图集】的发展和在房地产地籍【real estate cadastre】信息领域提供特别服务。 ） 课次序号： 4 Unit Four Distance Measurement 2 学时 一、本单元的重点难点： 1、主语从语 These velocities, which are affected by the air’s density, are reduced and need to be recalculated in the atmosphere. 2、强调比较级 If the distance is longer than the length of tape, then we can divide the long distance into several segments and get the total distance by plus each segment together. 二、对学生的要求： 1、必须掌握本单元的重点难点内容； 2、复习 pacing, precise ranging, distance measurement, by means of, a series of 3、掌握专业词汇 ① distance measuring instrument, rangefinder ② geodimeter ③ long-range EDM instrument