大地測量學與平面測量

1、Unit 2 Geodetic Surveying and Plane Surveying（大地測量與平面測量）Surveying has been traditionally defined as the art and science of determining the position of natural and artificial features on, above or below the earths surface; and representing this information in analog form as a contoured map, paper pla

2、n or chart, or as figures in report tables, or in digital form as a three dimensional mathematical model stored in the computer. （測量傳統(tǒng)定義為確定地表、地下和地上的自然與人工地貌特征【features形態(tài)、特征】；并使之按比例【in analog form】測繪成地形圖【contoured map】、平面圖【paper plan】或圖表，或形成報告圖表，或以數(shù)字形式形成三維立體數(shù)學模型存儲進計算機。）As such, the surveyor/geodesist

3、dealt with the physical and mathematical aspect of measurement. （同樣的，測量員/大地測量學家處理的就是測量出的物理的和數(shù)學的特征）The accurate determination and monumentation【標石、標志】 of points on the surface of the Earth is therefore seen as the major task. （因此精確確定并標定地表點位便成為測量的主要任務）Though these surveys are for various purposes, sti

4、ll the basic operations are the same-they involve measurements and computations or, basically, fieldwork and office work. （雖然測量工作有不同目的，基本的操作卻都一樣他們包括測量和計算，或更基本地稱之為，外業(yè)工作和內業(yè)工作）There are many different types of surveys such as land surveys, route surveys, city surveys, construction surveys, hydrographic

5、 surveys, etc., but generally speaking, surveying is divided into two major categories: geodetic and plane surveying. （測量分為許多不同的類型，如土地測量，路線測量，城市測量，建筑測量，水道測量等等，但是總的來說，測量分為兩個主要的種類：大地測量和平面測量）Surveys will either take into account the true shape of the Earth（Geodetic surveys）or treat the earth as a flat

6、surface(Plane surveys). （是考慮地球真實形狀的大地測量還是將地球當成一個平面的平面測量【緊跟著上句】）Additionally, surveys are conducted【表現(xiàn)】 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，測量還分為確定平面位置的水平測量和確定海拔的高程測量

7、或兩者的綜合。）Geodetic Surveying（大地測量）The type of surveying that takes into account the true shape of the earth is called geodetic surveying. （考慮地球真實形狀的測量工作稱為大地測量）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 c

8、ontrol for other surveys. （這種測量適用于大范圍和長距離的測量工作，用來確立基本點的精確位置，用以建立其他測量工作所需的控制網(wǎng)。）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.（在大地測量中，站點經(jīng)常是互相距離很遠，那么這種測量就比平面測量需要更精確

9、的儀器和測量方法。）Widely spaced, permanent monuments serve as the basis for computing lengths and distances between relative positions. （廣泛間隔開的永久標石就作為計算點位之間距離的基礎）【serve當作】These basic points with permanent monuments are called geodetic control survey points, which support the production of consistent and com

10、patible data for surveying and mapping projects.（這種永久標石點被稱為大地控制點，為測量和繪圖工作提供可靠和一致的數(shù)據(jù)）In the past, ground-based theodolites, tapes【卷尺】, and electronic devices were the primary geodetic field measurements used. （過去，大地經(jīng)緯儀【DJ大地經(jīng)緯儀的中文縮寫】、卷尺和電子設備是大地測量的野外工作初時【primary】的工具。）Today, the technological expansion

11、of GPS has made it possible to perform extremely accurate geodetic surveys at a fraction of the cost. （現(xiàn)在，GPS技術的發(fā)展【expansion擴充、膨脹】使大地測量工作花費非常小的代價【a fraction of一小部分】就能獲得極為精確的結果成為可能。）A thorough knowledge of the principles of geodesy is an absolute prerequisite for the proper planning and execution of

12、geodetic surveys.（大地測量工作計劃的編制【planning】和實施【execution】，【proper恰當?shù)?，翻譯時略掉】，絕對需要【absolute prerequisite】對大地測量學知識有全面的掌握?！続 thorough knowledge of the principles of geodesy is an absolute prerequisite 一個徹底的知識大地測量學的原理的，是絕對需要的?！浚㊣n Geodetic Surveys, the shape of the earth is thought of as a spheroid, although

13、 in a technical sense, it is not really a spheroid. （在大地測量中，地球的形狀被看成一個橢球體，雖然在技術角度來看，它不是真正的橢球。）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測量距離并不是沿著直線或平面進行，而是在一個曲面上。)Hence, in the computation of distanc

14、es in geodetic surveys, allowances are made for the earths minor and major diameters from which a spheroid of reference is developed. （因此，在大地測量距離的計算中，參考橢球的長軸與短軸所帶來的誤差就顯示【develop顯示出來】出來。）The position of each geodetic station is related to this spheroid. （每個大地站點的位置都與這個橢球有關）The positions are expressed

15、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.（這個位置是用緯度（與赤道面所成的角）和經(jīng)度（與初子午線所成的角）或用在直角坐標系中的北距和東距來表示。）A geodetic survey establishes the fundamentals for the determination of the surface and g

16、ravity field of a country. （大地測量為建立國家范圍內的重力場和確定地表架構提供【establishes建立】基礎）This is realized by coordinates and gravity values of a sufficiently large number of control points, arranged in geodetic and gravimetric networks.（這將由測定布設在大地網(wǎng)和重力網(wǎng)中數(shù)量十分巨大的控制點，所得到的坐標和重力值來實現(xiàn)）In this fundamental work, curvature and

17、the gravity field of the earth must be considered.（在這項基礎工作中，地球的曲率和重力場都應被考慮。）Plane Surveying（平面測量）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 surveyin

18、g.（這種類型的測量把地球平均的表面視作平面，或認為地球曲率帶來的誤差可以忽略不計，這樣的測量工作稱為平面測量significant重大的，不翻譯也行）The term is used to designate survey work in which the distances or areas involved are of limited extent.（這個術語曾指涉及的距離及范圍非常有限的測量工作【extent范圍】）With regard to horizontal distances and directions, a level line is considered mathe

19、matically 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.（由于被當成了水平距離和方向，水平線被當成直線【省略掉mathematically】，在這個有限范圍內所有點上的鉛垂線方向被認為是相同的，所有的角被認為都是平面角。）To make computations in plane surveying,

20、 you will use formulas of plane trigonometry, algebra, and analytical geometry. （在平面測量的計算中，你可以使用平面三角、代數(shù)、和平面解析幾何的公式）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. （小范圍內

21、，平面測量方法可以獲得精確的結果，但是隨著范圍的擴大，精度和準確度將隨之下降）For example, the length of an arc 18.5 km long lying in the earths 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 only 0.51 seco

22、nd for a triangle at the earths surface having an area of 100km2 . （例如，地球表面一條18.5km長的弧只比其所對的【subtend與相對】弦長7mm，【further進一步，可以省略】，在一個面積為100平方公里的平面三角形中的內角和與對應球面三角形中的內角和之差只有0.51秒）It will be appreciated that the curvature of the earth must be taken into consideration only in precise surveys of large area

23、s.（只有在大面積的精密測量工作中地球曲率才必需被考慮【appreciated重視】。）A great number of surveys are of the plane surveying type.（多數(shù)的測量工作都是屬于平面測量類型）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

24、 made to establish boundaries, except state and national. （【特定】區(qū)域測量、公路【highway是干道的意思，speedway、freeway才是高速公路】建設、鐵路、溝渠等，總的來說與人們工作密切相關的測量工作都是平面測量，不包括州界和國界測量在內的邊界測量也同屬平面測量）However, with the increasing size and sophistication of engineering and other scientific projects, surveyors who restrict their prac

25、tice to plane surveying are severely limited in the types of surveys in which they can be engaged.（然而，隨著工程和其他科學項目越來越大越來越復雜，在限定【restrict約束】于從事平面測量工作的測量員在他們可以從事的測量類型上受到嚴格【severely嚴格的】限制。【前面講多數(shù)測量工作為平面測量，這里就轉折的說從事平面測量的人員能進行的工作越來越少】）The operation of determining elevation usually is considered a division

26、of plane surveying. （我們通常把高程的測量與平面測量分開來。）Elevations are referred to the geoid.（高程參考的是大地水準面。【或者說高程是相對于大地水準面而言的】）The geoid is theoretical only.（大地水準面只是在理論上存在）It is the natural extension of the mean sea level surface under the landmass. （它是平均海平面在大陸下的自然延伸?！舅瞧骄Ｆ矫媛哟┻^大陸而成的】）We could illustrate this idea

27、 by digging an imaginary trench across the country linking the Atlantic and Pacific oceans.（我們可以通過挖掘一個的想象中的連通大西洋和太平洋溝渠【trench】來闡明【illustrate】這個概念。） If we allowed the trench to fill with seawater, the surface of the water in the trench would represent he geoid. （如果我們允許這條溝渠注滿海水，溝渠里的水面就代表大地水準面。）So for

28、all intents and purposes, the geoid is the same as mean sea level. （因此，從所有的目的和用途出發(fā)，【直譯：由于（為了？）所有的計劃和目標】大地水準面與平均海平面是一樣的。）【for引導原因】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記錄值的平均值。【直譯：平均海平面是指海水面的最高和最低記錄之間紀錄值的平均值?！浚￤e

29、 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. （我們用平均海平面作為一個數(shù)據(jù)，或不常用地和不準確地，當作一個基準面【datum plane】，通過它我們可以參考和描述地上、地表、地下的情況。）Imagine a true plane tangent to the surface of mean sea

30、level at a given point. （想象一個真正的平面與平均海平面在一個特定【given特定的、指定的】點上相切【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.（在離切點1km的地方，這個平面高于平均海平面的垂直距離為7.8cm?！緍epresent by通過描述】）Obviously, curvature of the earths surface is a factor that cannot be neglected in obtaining even rough values of elevations. （很明顯，即使在獲取粗略的高程值的時候，地球表面曲率也是一個不可忽略的因素。）The ordinary procedure in determining elevations, such as【像這樣