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 of natural and 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 survey
s) 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】
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，GPS技术的发展【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【expressed翻译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。【A thorough knowledge of the principles 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）

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