12大地测量学概念

Unit 12 Geodesy Concepts（大地测量学概念）

As we know, surveying is divided into two major categories: geodetic surveying and plane surveying.（我们知道，测量分为两个主要范畴【category种类、范畴】：大地测量和平面测量）

Geodetic surveying takes into account the true shape of the earth whereas plane surveying treats the earth as a flat surface.（大地测量要考虑【take into account考虑】地球的真实形状，而【whereas然而、可是】平面测量把地球视为【treat】一个平面）

The subject of this text aims at the study of the size and shape of the earth which refers to Geodesy.（这篇文章的主题【subject】针对【aim at】的就是涉及【refer to】大地测量学的地球的大小和形状的研究）

The expression “the size and shape of the earth” has various meanings in geodesy according to the way it is used and the precision with which the earth’s size and shape is to be defined.（依照【according to】定义地球大小和形状所使用的方法和精度，“地球的大小和形状”的表达在大地测量学中有各种各样的【various】含义）

The actual topographic surface is most apparent with its variety of landforms and water areas.（实际的地表【topographic地形的、地形学的surface表面这里直接译为地表】大多表现为地形【landform】和水域的多样性【variety】）【is most apparent with 副词短语做表语】

This is, in fact, the surface on which actual earth measurements are made.（事实上【in fact】，事实上，这就是所做的地球实际表面测量。）

It is not suitable, however, for exact mathematical computations because the formulas which would be required to take the irregularities into account would necessitate a prohibitive amount of computations.（然而，对于精确的【exact】数学计算这并不合适，因为需要考虑到【take into account】不规则【irregularity】的公式【formula】将需要

【necessitate需要、被需要】大量的【prohibitive非常高的、受抑止的、禁止的】计算）

The concept of geodesy should be mentioned first.（首先应该说一下【mention提及】大地测量学的概念）

From the Concise Oxford Dictionary: geodesy. n. The branch of mathematics dealing with the figures and areas of the earth or large portions of it.（简明【Concise简明的】牛津词典：大地测量学n.名词. 数学的一个分支，用来处理地球或其一大部分【portion一部分】的形状和区域）

Encyclopedia of Science and Technology, 2001 edition, Academic Press, 2000: Geodesy is a science, the oldest earth (geo-) science, in fact.（科学与技术百科全书【Encyclopedia 百科全书】，2001版，学术出版社【Academic Press】，2000：大地测量学是一门科学，事实上，是最古老的地球科学）

It was born of fear and curiosity, driven by a to predict natural happenings and calls for the understanding of these happenings.（受预知【predict】自然事件【现象】和要求理解这些事件【现象】的愿望所驱动，由恐惧和好奇而生。）

The classical definition, according to one of the “fathers of geodesy” reads: “geodesy is the science of measuring and portraying the earth’s surface” [Helmert, 1880, p.3].（经典【classical经典的、古典的】定义，依照“大地测量学之父”的其中一位的说法：“大地测量学是测量和描绘【portray】地球表面的科学”[Helmert, 1880, p.3] ）【Helmert 德国人赫尔默特（F.R.Helmert，1843—1917 ）首创海上重力测定】

Nowadays, we understand the scope of geodesy to be somewhat wider.（如今，我们理解大地测量学的范围【scope范围】就有些【somewhat有些】宽了）

It is captured by the following definition [Vanicek and Krakiwsky, 1986, p. 45]: “geodesy

is the discipline that deals with the measurement and representation of the earth, including its gravity field, in a three-dimensional time varying space.”（从下列定义就可以得知【capture俘获、获得，这里指可由下面的定义所了解】[Vanicek and Krakiwsky, 1986, p. 45]：“大地测量学是涉及【deal with】，在一个三维的时空中，测量和描述包括重力场在内的地球的一门学科【discipline学科】）

According to the classical definition of Helmert, geodesy is the “science of the measurement and m apping of the earth’s surface”.（依照赫尔默特的经典定义，大地测量学是“测量和绘制地球表面的科学”）

This definition has to this day retained its validity; it includes the determination of the earth’s external gravity field, as well as the surface of the ocean floor.（这个定义时至今日【to this day至今】还保留着【retain保留】它的有效性【validity有效性、正确性】；它包括地球的外部【external外部、外部的】重力场、也包括了海洋底部的表面的测定【determination这里翻译成测定】。）

With this definition, which as to be extended to include temporal variations of the earth and its gravity field, geodesy may be included in the geosciences, and also in engineering sciences, e.g., National Academy of Sciences (1978).（依照这个定义——关于【as to】被扩展包括时间变量【temporal时间的；variation变量】的地球和它的重力场，大地测量学可以被包括进地球科学、也可以被包括进工程学，例如【e.g.注意读音i:dgi】，国家科学院（1978））

So, we’ve learned that Geodesy is the discipline that deals with the measurement and representation of the earth, its gravity field and geodynamic phenomena (polar motion, earth tides, and crustal motion) in three-dimensional time varying space.（这样【so】，我们已经知道了大地测量学是关于在三维时空中测量和表述地球本身、它的重力场和

地球动力学【geodynamic】现象（极移【motion移动】，固体潮，和地壳【crustal】运动）的学科【discipline】）

Geodesy is primarily concerned with positioning and the gravity field and geometrical aspects of their temporal variations.（大地测量学主要涉及它们的时间变量【temporal 时间的；variation变量】的位置、重力场和几何外表）

Triggered by the development of space exploration, geodesy turned in collaboration with other sciences toward the determination of the surfaces of other celestial bodies (moon, other planets).（由于空间探索的发展的触发【Trigger】，大地测量学转而与其它科学合作【in collaboration with与……合作】，来【toward为了、向】确定其它天体【celestial body】（月球、其它行星）的表面）

The corresponding disciplines are called selenodesy and planetary geodesy.（其相应的学科被称为月面测量学【selenodesy】和行星大地测量学【planetary geodesy】）

Geodesy may be divided into three basic subdisciplines: geometric geodesy, physical geodesy, and space geodesy.（大地测量学可以分成三个基本分支：几何大地测量学、物理大地测量学、和空间大地测量学）

Geometric geodesy(also called astro-geodesy) concerns with determination of the size and shape of the earth as well as the position on the earth surface.（几何大地测量学（也称为天文大地测量学【astro-geodesy】）涉及确定地球大小和形状，还有地球表面上的位置的确定。）

For the purpose of deducing the size and shape of the earth and the precise location of specific positions on the earth’s surface, geometric geodesy considers the geoid through

the use of astrogeodetic methods.（为了【For the purpose of】推出【deduce】地球的大小和形状，还有地球表面上的明确【specific明确的】位置的精确定位【location位置、点位n.】，几何大地测量学考虑的是大地水准面，通过几何大地测量的方法）

This aspect of the science is involved with the basic principles of the establishment of the national geodetic networks which include both horizontal and vertical controls and strictly geometrical relationships measured in various ways: astronomic positioning, triangulation, trilateration, and traverse are four traditional surveying techniques in general use for determining the exact positions of points on the earth’s surface.（该学科【the science】的这个方面【aspect】涉及建立国家大地网的基本原理【basic principle】，包括水平和高程控制，并以不同方式【in various ways】严格测定几何关系：天文定位、三角测量、三边测量、导线测量是在确定地表点精确位置时通常的四种传统测量技术）

In recent years, modern technological developments have added several new methods utilizing artificial earth satellites. （近年来，现代科技的发展增加了几种利用【utilize 利用】人造地球卫星【artificial人造的】的新方法。）

Other methods relevant to geodetic surveying are being developed.（其它相关的【relevant 相关的】大地测量方法也得到发展）

Physical geodesy utilizes measurements and characteristics of the earth’s gravi ty field as well as theories regarding this field to deduce the shape of the geoid and in combination with arc measurements, the earth’s size.（物理大地测量学利用【utilize利用】测量和地球重力场特征还有关于重力场的理论，来推出大地水准面的形状；与弧度测量【arc measurement】相结合【in combination with与……结合】推出地球的大小）

With sufficient information regarding the earth’s gravity field, it is possible to determine geoidal undulations, gravimetric deflections, and the earth’s flattening.（利用涉及地球重

力场充分的【sufficient】信息【regarding涉及，介词prep.】，就可以确定大地水准面波动【undulations】、重力偏差【gravimetric deflection】、和地球扁率）

Space geodesy(Satellite geodesy) uses satellites for geodetic purposes which were advocated and published as early as 1956.（空间大地测量学（卫星大地测量学）把卫星用于大地测量的目的，早在【as early as早在】1956年就被提出【advocate】和发表【publish发表、出版】了）

With the constant growth of space technology, the development of electronic distance measuring devices, and the perfection of electronic data processing equipment, satellites specifically equipped for geodetic purposes have been developed, launched, observed and the data utilized.（随着空间技术的不断发展，电子测距仪的发展，和电子数据处理【electronic data processing电子数据处理】装置的完善【perfection】，特为【specifically 特别地】大地测量目的装备的卫星已经被发展、发射、观测和数据利用了【或译为：已经发展、发射、观测并其数据已得到应用了】）

Several observational systems, geodetic cameras, electronic ranging and Doppler Satellite Surveys were developed and improved.（几种观测系统，大地测量摄像机，电子测距和多普勒卫星测量被发展和改善了）

Some of the areas of new geodetic developments are: satellite laser ranging, lunar laser ranging, very long baseline interferometry, satellite radar altimetry, the Global Positioning System, satellite-to-satellite tracking, and inertial surveying.（一些新的大地测量发展的领域是：卫星激光测距，激光测月【lunar laser ranging】，甚长基线干涉测量【very long baseline interferometry】，卫星雷达测高【satellite altimetry卫星测高】，全球定位系统，卫星跟踪卫星技术【satellite-to-satellite tracking卫星跟踪卫星技术】，惯性测量【inertial surveying】）

The major goals of geodesy can be summarized as follows [Vanicek and Krakiwsky, 1986]: （大地测量学的主要目的可以概述为如下：[Vanicek and Krakiwsky, 1986]）

1.Establishment and maintenance of national and global three-dimensional geodetic

control networks on land, recognizing the time-variant aspects of these networks.

（陆地上国家和全球三维大地测量控制网的建立和维护，这些控制网的时间变量【time-variant】方面的认知。）

2.Measurements and representation of geodynamic phenomena (polar motion, earth tides,

and crustal motion).（地球动力学现象（极移、固体潮、地壳运动）的测量和表述）3.Determination of the gravity field of the earth including temporal variations.

（含时间变量的地球重力场的测定）