测绘专业英语翻译第二单元

Unit 2 Geodetic Surveying and Plane Surveying（大地测量与平面测量）Surveying has been traditionally defined as the art and science of determining the position ofnatural and artificial features on, above or below the earth’s surface; and representing thisinformation 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；并使之按比例测绘成地形图、平面图或图表，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 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）Additionally, surveys are conducted 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）These basic points with permanent monuments are called geodetic control survey points, whichsupport 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 , and electronic devices were the primary geodetic field measurements used. （过去，大地经纬仪、卷尺和电子设备是大地测量的野外工作初时的工具。）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使大地测量工作花费非常小的代价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和实施，绝对需要对大地测量学知识有全面的掌握。）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 referenceis 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。）

Plane Surveying（平面测量）

The type of surveying in which the mean surface of the earth is considered a plane, or in whichthe 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）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）With regard to

horizontal distances and directions, a level line is considered mathematically straight, the direction of theplumb 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，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 planesurveying 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 differencebetween 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弦长7mm，further，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）。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 beingsare plane surveys, as are the surveys made to establish boundaries, except state and national.

（区域测量、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限制。）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。）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来阐明这个概念。）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，大地水准面与平均海平面是一样的。）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。）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，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 thesurface 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点上相切）。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。）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 balancing backsight and foresight distance in differential leveling, automatically takes into account the curvature of theearth 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，在微差水准测量中平衡前后视距，地球曲率和大气折光影响将被自动考虑和低偿，不必经测量者额外改正，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的工作所利用）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，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。）