測(cè)繪工程專業(yè)英語(yǔ)課文全部翻譯19頁(yè)

1、Section 2 The Reliability of a Survey and Errors測(cè)量誤差的可靠性Since every technique of measurement is subject to unavoidable error, surveyors must be aware of all sources and types of error and how they combine. If the accuracy of a measurement is defined as the nearness of that value to its true value (a

2、 quantity we can never know) then a surveyor must ensure that the techniques he chooses will produce a result that is sufficiently accurate. He must know, therefore, how accurate he needs to be, how to achieve this accuracy and how to check that the required accuracy has been achieved. 由于每個(gè)測(cè)量技術(shù)是不可避免

3、的誤差，測(cè)量員必須知道的所有誤差的來(lái)源和類型，以及它們是如何結(jié)合。如果測(cè)量的準(zhǔn)確性，其真正的值（我們可以永遠(yuǎn)不知道的數(shù)量）的接近程度，該值被定義為，然后測(cè)量員必須確保他選擇的技術(shù)將產(chǎn)生一個(gè)結(jié)果，是足夠精確的。因此，他必須知道他需要的精度如何，如何實(shí)現(xiàn)這一目標(biāo)的準(zhǔn)確性和如何檢查所要求的精度已經(jīng)達(dá)到。Accuracy requiredWhen surveying to produce a plan, the accuracy required is defined by the scale of the plot, since there should be no plottable error

4、in the survey data. A good draughtsman can plot a length to within 0.25 mm and so, if a plan of an area is required at a scale of 1/1000, i.e., 1 mm on the plan represents 1 m on the ground, the smallest plottable distance is 0.25 m. Thus, for a survey at 1/1000 scale, all the measurements must be t

5、aken such that the relative positions of any point with respect to any other must be determined to 0.25 m or better.當(dāng)測(cè)量一個(gè)平面時(shí),精度通常是根據(jù)展圖比例決定的，因?yàn)樵诶L圖中不能有測(cè)量誤差。一個(gè)好的繪圖員可以在大約0.25毫米的范圍內(nèi)畫圖，假如一個(gè)地區(qū)的圖紙比例尺要求是1/1000，即1毫米圖上距離代表1米實(shí)地距離，那么最小的測(cè)距應(yīng)該是0.25米。因此，對(duì)于1/1000比例尺的測(cè)量，所有測(cè)量必須保證任意一點(diǎn)與其他任一點(diǎn)的相對(duì)位置不得大于0.25米。The specificati

6、ons of surveys for other purposes such as engineering works or property boundary definition might well be determined by engineering tolerances or legal standards. 基于測(cè)量規(guī)范可能被用于其他目的，如工程測(cè)量或財(cái)產(chǎn)邊界的測(cè)量將由工程限差和合法的基準(zhǔn)決定。Achieving the specificationTo ensure that the specification is achieved the equipment and met

7、hods must be chosen such that, not only will they collect the right sort of data, i.e., the correct combination of angles and distances, but that the data will be to the required accuracy. There are several types of error that occur and a knowledge of their importance and characteristics is essentia

8、l in the understanding of the limitations of the techniques of measurement. The salient features will be stated now but further information is given in later chapters. 為了確保測(cè)量符合規(guī)范，儀器和數(shù)據(jù)應(yīng)按照以下要求進(jìn)行，并不是只是得到正確的數(shù)據(jù)，即更正角和邊的關(guān)系，從而得到的數(shù)據(jù)滿足精度的要求。在測(cè)量中有幾種類型的誤差，掌握它們的重要性和特性對(duì)于理解測(cè)量技術(shù)的限差是必不可少的。本章主要講解這些誤差的主要特征，后面的章節(jié)將提供進(jìn)一

9、步的闡述。Mistakes 粗差Blunders or mistakes are often inaccurately referred to as gross errors. Miscounting the number of tape lengths when measuring a long distance or transposing numbers when booking are two very simple, but all too common, examples of mistakes. These types of mistakes can occur at any s

10、tage of a survey, when observing, booking, computing or plotting, and they would obviously have a very damaging effect on the results if left uncorrected. However, by following strictly a well-planned observing procedure it is possible to reduce the number that occur and then independent checks at e

11、ach stage should show up those that have been made. In practice, none should ever go undetected and uncorrected. 錯(cuò)誤經(jīng)常不準(zhǔn)確的理解為粗差。 當(dāng)測(cè)量很長(zhǎng)一段距離時(shí)，讀錯(cuò)尺的讀數(shù)或記錄兩個(gè)簡(jiǎn)單的數(shù)時(shí)顛倒它們的位置，這些都是很常見的錯(cuò)誤例子。這些類型的誤差可以發(fā)生在測(cè)量任何階段，當(dāng)觀測(cè)，記錄，計(jì)算和繪圖，如果不糾正這些錯(cuò)誤，他們?cè)诮Y(jié)果上顯然有一個(gè)非常有害的影響。但是，通過(guò)嚴(yán)格周詳?shù)挠^測(cè)過(guò)程，可能杜絕這些錯(cuò)誤的產(chǎn)生，然后在每個(gè)階段應(yīng)獨(dú)立檢測(cè)可以是這些錯(cuò)誤顯現(xiàn)出來(lái)。在實(shí)踐中，沒有不可發(fā)現(xiàn)和

12、不可糾正的粗差。Systematic errors系統(tǒng)誤差Systematic errors arise from sources which act in a similar manner on observations. The method of measurement, the instruments used and the physical conditions at the time of measurement must all be considered in this respect. Expansion of steel tapes, frequency changes

13、in electromagnetic distance measuring (EDM) instruments and collimation in a level are just a few examples of possible sources of systematic errors.系統(tǒng)誤差的來(lái)源于以相同的觀測(cè)方式。測(cè)量時(shí)要考慮這些方面，測(cè)量的方法、測(cè)量?jī)x器和外界環(huán)境。鋼尺的膨脹，電磁測(cè)距儀的頻率變化和水準(zhǔn)儀的照準(zhǔn)情況都是系統(tǒng)誤差的可能來(lái)源。These errors are of vital importance in activities which consist of add

14、ing together a succession of individual observations (see sections on leveling and traversing). If all the individual measurements contain the same type of systematic error, which by their nature always act in the same direction, then the total effect is the sum of them all.這些誤差在由一系列獨(dú)立觀測(cè)（參見水準(zhǔn)測(cè)量和導(dǎo)線測(cè)量

15、部分）累加在一起組成的測(cè)量值中極為重要，如果所有的獨(dú)立測(cè)量包含相同類型的系統(tǒng)誤差，且這些系統(tǒng)誤差總是表現(xiàn)出相同的性質(zhì)，那么總影響是所有這些的總和。It must be ensured that measurements are as accurate as required by removing the effects of all factors that, if neglected, would result in a significant error. The errors caused by some factors can be eliminated with the corre

16、ct observing procedure and others countered by applying corrections. Systematic errors are not revealed by taking the same measurement again with the same instruments. The only way to check adequately for systematic error is to remeasure the quantity by an entirely different method using different i

17、nstruments.通過(guò)消除所有因素的影響確保精度滿足要求。如何忽略這些因素將會(huì)導(dǎo)致重大的錯(cuò)誤。通過(guò)正確的觀測(cè)程序以及糾正計(jì)算可以消除誤差。通過(guò)同樣的儀器用同樣的方法測(cè)量是檢測(cè)不出系統(tǒng)誤差的。唯一能充分檢測(cè)系統(tǒng)誤差就是重測(cè)這些量通過(guò)使用完全不同的測(cè)量方法和測(cè)量?jī)x器。Random errorsRandom errors are really all those discrepancies remaining once the blunders and systematic errors have been removed. Even if a quantity is measured many

18、 times with the same instrument in the same way, and if all sources of systematic error have been removed, it is still highly unlikely that all results will be identical. The differences, caused mainly by limitations of instruments and observers, are random errors.隨機(jī)誤差事實(shí)上是除去粗差和系統(tǒng)誤差后。即使測(cè)定數(shù)量很多次以同樣的方式與

19、相同的儀器，和已被刪除，如果所有系統(tǒng)誤差的來(lái)源，它仍然是極不可能的，所有的結(jié)果將是相同的。的差異，主要儀器和觀察員的限制造成的，是隨機(jī)的誤差。It is found in practice that these errors, although called random, have the following characteristics:(1) small errors occur more frequently than large ones(2) positive and negative errors are equally likely to occur(3) very larg

20、e errors seldom occur.在實(shí)踐中發(fā)現(xiàn)，這些誤差，雖然稱為隨機(jī)的，具有以下特點(diǎn)：（1） 小誤差發(fā)生的頻率比大（2）正面和負(fù)面的誤差發(fā)生的可能性相同（3）非常大的誤差很少發(fā)生。These characteristics are typical of errors which are normally distributed and it is assumed that we can use the mathematical theory based on the normal distribution to deal with the errors met with in su

21、rveying. 正態(tài)分布是這些誤差典型的特點(diǎn)是，我們可以用基于正態(tài)分布的數(shù)學(xué)理論來(lái)處理這些測(cè)量中的誤差。Understanding the errors that limit the accuracy of the measurement techniques is but one step to ensuring specifications are achieved, as will be seen when the methods of survey are described:了解限定測(cè)量方法精度的誤差僅僅是確保滿足測(cè)量規(guī)范的一步，按照如下的測(cè)量方法進(jìn)行：(a) The survey

22、 area is always totally covered with the simplest possible framework of high quality measurements. If the rest of the survey work is carried out within this control the possible damaging accumulation of errors can be contained. This is often termed working from the whole to the part,（a） 測(cè)區(qū)總是由高精度的測(cè)量框

23、架所覆蓋。如果剩下的測(cè)量工作在這個(gè)控制網(wǎng)內(nèi)進(jìn)行的話，累積誤差就可以得到有效地控制。這通常被稱為“從整體到的部分的工作，(b) Observing procedures are designed so that (i) most mistakes that occur are discovered immediately and (ii) possible sources of systematic errors eliminated. （b）觀測(cè)程序設(shè)計(jì)，（）大多數(shù)誤差及時(shí)被發(fā)現(xiàn)，（ii）系統(tǒng)誤差得到有效地控制。(c) Additional, or redundant, observation

24、s are taken so that all data can be checked for the mistakes, systematic errors and random errors that do occur. For example, the three angles of a triangle would be observed although only two are required to define the shape. The third angle could be deduced but, when measured, acts as a check.（c）多

25、余的觀測(cè)是用來(lái)檢測(cè)粗差、系統(tǒng)誤差、偶然誤差的。例如，一個(gè)三角形觀測(cè)中，只要觀測(cè)兩個(gè)角就能決定其形狀。但第三角度的觀測(cè)是用來(lái)檢核的。(d) Many quantities are observed several times. These repeated measurements and the observation of redundant data serve both as checks and to improve on the precision of the final results. （d）許多數(shù)據(jù)需要多次觀測(cè)。重復(fù)觀測(cè)是用來(lái)檢核并提高最終精度的。Checking the s

26、urveyEven with all the checking procedures the surveyor employs, errors can still occur in the finished plan and for this reason final independent checks are required. For simple work this would involve inspecting the final plan in the field and comparing some measurements scaled off the plan with t

27、heir equivalents on the ground.雖然測(cè)量員按照檢核步驟進(jìn)行檢核，但是誤差仍然可以出現(xiàn)在最后的平面圖中所以最后還需要進(jìn)行獨(dú)立檢核。對(duì)于這項(xiàng)簡(jiǎn)單的測(cè)量工作，需要到野外進(jìn)行最后的平面圖紙的檢核和圖紙距離放到實(shí)地進(jìn)行比對(duì)。Angle and Direction Measurement角度和方向測(cè)量Horizontaland vertical angles are fundamental measurements in surveying.It is necessary to be familiar withthe meanings of certain basic ter

28、ms before describing angle and direction measurement. The terms discussed here have reference to the actual figure of the earth.水平角和豎直角是測(cè)量的基本測(cè)量工作,在描述角度和方向測(cè)量之前，有必要熟悉幾個(gè)基本術(shù)語(yǔ)的含義,這里討論的這些術(shù)語(yǔ)與地球的真實(shí)形狀有關(guān). Basic Terms基本術(shù)語(yǔ)A vertical line at any point on the earths surface is the line that follows the direction

29、of gravity at that point. It is the direction that a string will assume if a weight is attached at that point and the string is suspended freely at the point. At a given point there is only one vertical line.A horizontal line at a point is any line that is perpendicular to the vertical line at the p

30、oint. At any point there are an unlimited number of horizontal lines.A horizontal plane at a point is the plane that is perpendicular to the vertical line at the point.There is only one horizontal plane through a given point. A vertical plane at a point is any plane that contains the vertical line a

31、t the point. There are an unlimited number of vertical planes at a given point.地球表面任一點(diǎn)的垂線是指這點(diǎn)上沿著重力的方向的線,如果在這點(diǎn)上用線懸掛一個(gè)重物，當(dāng)線自由靜止時(shí)，這條線所呈現(xiàn)的方向即重力方向。在給定的一個(gè)點(diǎn)上只有一條垂線。一點(diǎn)上的水平線是垂直于過(guò)該點(diǎn)的垂線的直線。過(guò)任一點(diǎn)的水平線有無(wú)數(shù)條。過(guò)一點(diǎn)的水平面是垂直于過(guò)該點(diǎn)的垂線的平面,過(guò)給定的一個(gè)點(diǎn)只有一個(gè)水平面.過(guò)一點(diǎn)的豎直面是包含過(guò)該點(diǎn)的垂線的任一平面過(guò)給定的一點(diǎn)有無(wú)數(shù)個(gè)豎直面. Horizontal Angle and Vertical Angle水平

32、角和豎直角A horizontal angle is the angle formed in a horizontal plane by two intersecting vertical planes, or a horizontal angle between two lines is the angle between the projections of the lines onto a horizontal plane. For example, observations to different elevation points B and C from A will give t

33、he horizontal angle bac which is the angle between the projections of two lines (AB and AC) onto the horizontal plane. It follows that,although the points observed are at different elevations, it is always the horizontal angle and not the space angle that is measured .The horizontal angle is used pr

34、imarily to obtain relative direction to a survey control point, or topographic detail points, or points to be set out. A vertical angle is an angle measured in a vertical plane which is referenced to a horizontal line by plus (up) or minus (down) angles, or to a vertical line from the zenith directi

35、on. Plus and minus vertical angles are sometimes referred to as elevation or depression angles respectively. A vertical angle thus lies between 0 and 90.Zenith is the term describing points on a celestial sphere that is a sphere of infinitely large radius with its center at the center of the earth.

36、The zenith is an angle measured in a vertical plane downward from an upward directed vertical line through the instrument. It is thus between 0 and 180.水平角是指在一個(gè)水平面內(nèi)由兩相交的豎直面形成的角，或者說(shuō)，兩條線之間的水平角是這兩條線在水平面上的投影線的夾角.例如，在A點(diǎn)觀測(cè)不同高度的B和C點(diǎn)，其水平角bac是由AB和AC兩條線在水平面上的投影構(gòu)成的.由此得出結(jié)論結(jié)論，雖然被觀測(cè)的點(diǎn)在不同的高度上，測(cè)出的總是水平角而不是空間角。水平角主要用

37、來(lái)由聯(lián)測(cè)控制點(diǎn)獲得相對(duì)方向，或者地形測(cè)量碎部點(diǎn)、或者放樣點(diǎn),豎直角是在一個(gè)豎直面內(nèi)參考于水平線的正（仰）角或負(fù)（俯）角，或者相對(duì)于一個(gè)天頂方向的垂線的角.正負(fù)豎直角有時(shí)分別被稱為仰角或俯角.Obviously the zenith angle is equal to 90 minus the vertical angles. Vertical angles or zeniths are used in the correction of slope distance to the horizontal or in height determined. For the most part, th

38、e instrument used in the measurement of angles is called a transit or theodolite, although angles can be measured with clinometers, sextants (hydrographic surveys), or compasses. The theodolite contains a horizontal and vertical circles of either glass or silver. The horizontal and vertical circles

39、of theodolite can be linked to circular protractors graduated from 0 to 360 in a clockwise manner set in horizontal and vertical plane. The horizontal circle is used when measuring or laying off horizontal angles and the vertical circle is used to measure or lay off vertical angles or zenith angles.

40、 Usually the units of angular measurement employed in practice are degrees, minutes, and seconds, the sexagesimal system. 豎直角位于090度之間.天頂方向是一個(gè)術(shù)語(yǔ)，用來(lái)描述在天球上的點(diǎn)，天球是一個(gè)半徑無(wú)限大的球，其中心在地球中心。天頂距是一個(gè)在豎直面內(nèi)從一個(gè)過(guò)儀器的被定向?yàn)橄蛏系呢Q直方向線向下測(cè)量的角。它的范圍是從0到180度。顯然，天頂距等于90度減去豎直角.豎直角或天頂距用于斜距化平距的改正或者高程的測(cè)量.在極大程度上，用來(lái)測(cè)角的工具被稱為經(jīng)緯儀，雖然角度可以用傾斜儀

41、、六分儀、或羅盤儀來(lái)測(cè)，經(jīng)緯儀有一個(gè)玻璃的或鍍銀的水平度盤和豎直度盤.經(jīng)緯儀的水平度盤和豎直度盤與順時(shí)針刻了0到360度刻劃的圓分度器相連。測(cè)或撥水平角時(shí)用水平度盤，測(cè)或撥豎直角或天頂距時(shí)用豎直度盤，通常角度測(cè)量法使用的單位是六十進(jìn)制的度、分、秒。Angle Measurement角度測(cè)量A horizontal angle in surveying has a direction or sense; that is, it is measured or designed to the right or to the left, or it is considered clockwise or

42、 counterclockwise. In the above figure, the angle at A from B to C is clockwise and the angle from C to B is counterclockwise. With the theodolite set up, centered, and leveled over at station A, then a simple horizontal angle measurement between surveying point B, A and C would be taken as follows:

43、在測(cè)的水平角有方向，就是說(shuō)它是向左測(cè)還是向右測(cè)，或者是說(shuō)，順時(shí)針測(cè)還是逆時(shí)針測(cè).如上圖所示，在A點(diǎn)由B到C就是順時(shí)針角，而從C到B就是逆時(shí)針角，經(jīng)緯儀在A點(diǎn)安置、對(duì)中、整平后，在B、A和C測(cè)量點(diǎn)間的簡(jiǎn)單的水平角測(cè)量可以按下列步驟進(jìn)行： Commencing on , say, “face left”, the target set at survey point B is carefully bisected and the reading on horizontal scale is 25. The upper plate clamp is released and telescope is

44、 turned clockwise to survey point C. The reading on horizontal circle is 75The horizontal angle is then the difference of the two directions, i.e. (75-25) =50說(shuō)示意，“盤左”，將B點(diǎn)的目標(biāo)仔細(xì)分中，水平度盤讀數(shù)為25度水平度盤制動(dòng)螺旋松開，順時(shí)針轉(zhuǎn)動(dòng)望遠(yuǎn)鏡至C點(diǎn)，水平度盤讀數(shù)75度水平角就是兩個(gè)方向值的差值，即， (75-25) =50Change face and observe point C on “face right”, and

45、 note the reading=255Release upper plate and swing counterclockwise to point B and note the reading =205The reading or the direction must be subtracted in the same order as 255-205=50The mean of two values would be accepted if they are in acceptable agreement.換度盤方向至盤右并照準(zhǔn)C點(diǎn)，記下讀數(shù)為255度松開水平度盤，逆時(shí)針旋轉(zhuǎn)至B點(diǎn)并記

46、下讀數(shù)為205度讀數(shù)或者說(shuō)是方向值按同樣的法則相減，255-205=50如果兩個(gè)減出來(lái)的值的一致性是可接受的，取兩個(gè)值的平均值。Modern electronic digital theodolites contain circular encoders that sense the rotations of the spindles and the telescope, convert these rotations into horizontal and vertical (or zenith) angles electronically, and display the value of

47、 the angles on liquid crystal displays (LCDs) or light-emitting diode displays (LEDs). These readouts can be recorded in a conventional field book or can be stored in a data collector for future printout or computation. The instrument contains a pendulum compensator or some other provision for index

48、ing the vertical circle readings to an absolute vertical direction.The circle can be set to zero readings by a simple press of a button or initialized to any value on the instrument. Azimuth is the horizontal angle measured in a clockwise direction from the plane of the meridian, which is a line on

49、the mean surface of the earth joining the north and south poles. Azimuth ranges in magnitude from 0 to 360, values in excess of 360, which are sometimes encountered in computations, are simply reduced by 360 before final listing. Bearing is the traditional way of stating the orientation of the line.

50、 It is actually the angle measured from the north or south.The bearing, which can be measured clockwise or counterclockwise from the north or south end of the meridian, is always accompanied by letters that locate the quadrant in which the line falls. For example, bearing N32W indicates a line trend

51、ing 32 west of the north.It is equal to an azimuth of 328. Bearing S12W indicates a line trending 12 west of the south. It is equal to an azimuth of 192. It is important to state that the bearing and azimuth are respect to true north.現(xiàn)代的電子數(shù)字經(jīng)緯儀包含編碼度盤，能夠感知軸和望遠(yuǎn)鏡的旋轉(zhuǎn)，并使之電子地轉(zhuǎn)換為水平角度和豎直角度，并在液晶顯示器或發(fā)光二極管顯示器上

52、顯示出來(lái)，這些顯示可以被一個(gè)傳統(tǒng)的野外電子手簿或數(shù)據(jù)收集器記錄，以便日后打印或計(jì)算。這種儀器具有一個(gè)懸掛補(bǔ)償器或其它裝置，使豎盤指標(biāo)讀數(shù)指向一個(gè)絕對(duì)豎直方向，這個(gè)度盤可以通過(guò)簡(jiǎn)單的按一個(gè)鍵就將其置零，或初始化成任一值。方位角是從子午面起算按順時(shí)針旋轉(zhuǎn)的角，子午線是在地球平均表面連接北極與南極的線。方位角的取值范圍從0度到360度，超過(guò)360的值有時(shí)會(huì)在計(jì)算時(shí)遇到，只需減去360度即可。方向角是一種傳統(tǒng)的描述直線方向的方法。實(shí)際上，它是從南或北方向開始量測(cè)的角，方向角可以從子午線，北端或南端以順時(shí)針或逆時(shí)針量測(cè)，總是伴以字母，用來(lái)標(biāo)明直線所落在的象限。方向角N32W代表一條直線從北方向轉(zhuǎn)向西方向

53、32度，它等于方位角328度，方向角S12W代表一條直線從南方向轉(zhuǎn)向西方向12度，它等于方位角192度。需要重點(diǎn)說(shuō)明的是，方向角和方位角所用的是真北方向。 Unit 5 Traversing （導(dǎo)線測(cè)量）The purpose of the surveying is to locate the positions of points on or near the surface of the earth.（測(cè)量的目的是確定地表或接近地表的點(diǎn)的點(diǎn)位。）To determine horizontal positions of arbitrary points on the earths surfa

54、ce and elevation of points above or below a reference surface are known as a control survey.（確定地表任一【arbitrary任意的】點(diǎn)的平面位置和確定點(diǎn)高于或低于一個(gè)參考面的高程的工作被稱為控制測(cè)量）The positions and elevations of the points make up a control network.（這些點(diǎn)的平面位置和高程組成了一個(gè)控制網(wǎng)）There are different types of control networks depending on wher

55、e and why they are established.（依照它們建立的地點(diǎn)和目的不同，有不同的控制網(wǎng)類型）A control network may have very accurate positions but no elevations (called a Horizontal Control Network) or very accurate elevations but no positions (called a Vertical Control Network).（一個(gè)控制網(wǎng)可能有精確的平面位置而沒有高程（稱為平面控制網(wǎng)），或者有精確的高程而沒有平面位置（稱為高程控制網(wǎng)）

56、Some points in a control network have both accurate positions and elevations.（有些控制網(wǎng)的點(diǎn)既有精確的平面位置也有精確的高程）Control networks range from small, simple and inexpensive to large and complex and very expensive to establish.（控制網(wǎng)的范圍從小的、簡(jiǎn)單的、便宜的網(wǎng)到大的、復(fù)雜的、昂貴的網(wǎng)）A control network may cover a small area by using a “l(fā)o

57、cal” coordinate system that allows you to position the features in relation to the control network but doesnt tell you where the features are on the surface of the earth, or cover a large area by consisting of a few well-placed and precise-established control points, which is sometimes called the pr

58、imary control.（一個(gè)控制網(wǎng)可以是覆蓋小范圍，使用區(qū)域坐標(biāo)系統(tǒng)，允許你相對(duì)于控制網(wǎng)確定地貌特征【feature】，但卻不告訴你它們?cè)诘乇淼氖裁吹胤?；或者覆蓋一個(gè)廣大區(qū)域，由少數(shù)被適當(dāng)安置并精確測(cè)設(shè)的控制點(diǎn)組成，有時(shí)被稱為基礎(chǔ)控制）The horizontal positions of points in a network can be obtained in a number of different ways.（控制網(wǎng)的點(diǎn)的平面位置可以由許多不同方法來(lái)獲得）The generally used methods are triangulation, trilateration,

59、traversing, intersection, resection and GPS.（一般使用的方法有，三角測(cè)量、三邊測(cè)量、導(dǎo)線測(cè)量、交會(huì)測(cè)量、后方交會(huì)測(cè)量、和GPS測(cè)量）The main topic of this text refers to the traversing.（這篇課文主要講的是導(dǎo)線測(cè)量）Triangulation（三角測(cè)量）The method of surveying called triangulation is based on the trigonometric proposition that if one side and three angles of a triangle are known, the remaining sides can be compu