測繪工程 外文翻譯

1、外文資料Level Rods and LenelsThere are many kinds of lenel rods available.Some are in one piece and others (for ease of transporting are either telescoping or hinged.Level rods are usually made of wood and are graduated from zero at the bottom.They may be either selfreading rods that are read directly t

2、hrough the telescope or targetrods where the rodman sets a sliding target on the rod and takes the reading directly. Most rods serve as either self-reading or as target rods.Among the several types of level rods available are the Philadelphia rod,the Chicago rod, and the Florida rod. The Philadelphi

3、a rod, the most common one, is made in two sections. It has a rear section that slides on the front section. For readings between 0 and 7 ft, the rear section is not extended; for reading between 7 and 13 ft, it is necessary to extended the rod. When the rod is extended,it is called a high rod. The

4、Philadelphia rod is distinctly divided into feet, tenths, and hundredths by means of alternating black and white spaces painted on the rod.The Chicago rod is 12 ft long and is graduated in the same way as the Philadelphia rod, but it consists of three sliding section. The Florida rod is 10 ft long a

5、nd is graduated in white an red stripes, each stripe being 0.10 ft wide. Also available for ease of transportation are tapes or ribbons of waterproofed fabric which are marked in the same way that a regular level rod is marked and which can be attached to ordinary wood strips. Once a job is complete

6、d, the ribbon can, be removed and rolled up. The wood strip can be thrown away. The instrumentman can clearly read these various level rods through his telescope for distances up to 200 or 300 ft, but for greater distances he must use a target. A target is a small red and white piece of metal attach

7、ed to the rod. The target has a vemier that enables the rodman to take a reading to the nearest 0.001 ft.If the rodman is taking the readings with a target and if the line of sight of the telescope is above the 7-ft mark, it is obvious that he cannot take the reading directly in the normal fashion.

8、Therefore, the back face of the rod is numbered downwardfrom 7 to 13 ft. The target is set at acertain mark on the front face of the rod and as the back section is pushed upward, it runs under an index scale and a vernier which enables the rodman to take the reading on the front.Before setting up th

9、e level the instrumentman should give some though to where he must stand in orde to make his sights. In other words, he will consider how to place the tripod legs so that he can stand comfortably between them for the lay-out of the work that he has in mind.The tripod is desirably placed in solid gro

10、und where the instrument will not settle as it mose certainly will in muddy or swampy areas. It may be necessary to provide some special support for the instrument, such as stakes or a platform. The tripod legs should be well spread apart and adjustde so that the footplate under the leveling screws

11、is approximately level. The insatrumentman walks around the instrument and pushes each leg frimly into the ground. On hillsides it is usually convenient to place ong leg uphill and two downhill.After the instrument has been levelde as much as possible by adjusting the tripod legs, the telescope is t

12、urned over a pair of opposite leveling screws if a four-screw instrument is being used.Then the bubble is roughly centered by turning that pair of screw in opposite directions to each other. The bubble will move in the direction of the left thumb. Next, the telescope is turned over the other pair of

13、 leveling screws and the bubble is again roughly centered. The telescope is turned back iver the first pair and the bubble is again roughly centered, and so on. This process is repeated a few more times with increasing care untill the bubble is centered with the telescope turned over either pair of

14、screws. If the level is properly sdjusted, the bubble should remain centered when the telescopeis turued in any direction. It is to be expected that there will be a slight maladjustment of the instrument that will result in a slight movement of the bubble; however, the precision of thework should no

15、t be adversely affected if the bubble is centered each time a rod reading is taken.The first step in leveling a three-screw instrument is to turn the telescope untill the bubble tube is parallel to two of the screws. The bubble is centered by turning these two screws in opposite directions.Next, the

16、 telescope is turned so that the bubble tube is perpendicular to a line through screws. The bubble is centered by turning screw .These steps are repeated untill the bubble stays centered when the telescope is turned back and forth.Electronic Distance MeasurementsA major advance in surveying in recen

17、t years has been the development of electronic distance-measuring instruments (ED-MIs. These devices determine lengths based on phase changes that occur as eletromagnetic energy of known wavelength travels from one end of a line to the other and returns.The potential value of these early EDM models

18、to the Surveying profession was immediately recognized: houever, they were expensive and not readily portable for field operations. Furthermore, measuring procedures were lengthy and mathematical reductions to obtain distances from observed values were difficult and time-consuming. In addition. The

19、range of operation of the first geodimeter was limited in daytime use. Continued research and development have overcome all these deficiencies.The chief advantages of electronic surveying are the speed and accuracy with which distances can be measured. If a line of sight is available, long or short

20、lengths can be measured over bodies of water or terrain that is inaccessible for taping. With modern EDM equipment, distance are automatically displayed in digital form in feet or meters, and many have built-in microcomputers that give results internally reduced to horizontal and vertical components

21、. Their many significant advantages haverevolutionized surveying procedures and gained worldwide acceptance. The long-distance measurements possible with EDM equipment make use of radios for communication, which is an absolute necessity in modern practice.One syetem for classifying EDMIs is by wavel

22、ength of transmitted electromagnetic energy ; the following categories exist :Electro-optical instruments Which transmit either modulatedlaser or infrared light having wavelengths within or slightly beyond the visible region of the spectrum.Microwave equipments Which transmits microwaves with freque

23、ncies in the range of 3 to 35 GHz corresponding to wavelengths of about 1.0 to 8.6 mm.Another classification system for EDMIs is by operational range . It is rather subjective , but in general two divisions fit into this system : short and medium range .The short-range group includes those devices w

24、hose macimum measuring capability does not exceed about 5km . Most equipment in this division is the electro optical type and uses infrared light . These instruments are small, portable, easy to operate, suitable for a wide variety of field surveying work, and used by many practitioners.Instruments

25、in the medium-range group have measuring capabilities extending to about 100 km and are either the electro-optical (using laser light or microwave type. Although frequently used in precise geodetic they are also suitable for land and engineering surveys. Longer-range device also available can measur

26、e lines longer than 100km,but they are nit generally used in ordinary surveying work. Most operate by trasmitting long radio waves, but some employ microwaves. They are used primarily in oceanogaraphic and hydrograpgic surving and navigation.In general, EDM equiment measures distances by comparing a

27、line of unkown length to the known wavelength of modulated electromagnetic energy. This is similar to relating a needed distance to the calibrated length of a steel tape.Electromagnetic energy propagates through the atmosphere in accordances with the following equation:V=f (1Where Vis the velocity o

28、f electromanetic energy, in meters per second;f the modulatedfrequency of the energy ,in hertz, and the wavelenth, in meteres.With EDMIs frequency can be precisely controlled but velocity varies with atmophere temperature, pressure,and humidity. Thus wavelength and frequency must vary in conformance

29、 with EQ.(1. For accurate electronic distance measuement, therefor., the atmosphere must be sampled and corrctios made accordingly.The generalizedprocedure of measuring distance electronically is depicted in Fig.8-1. an edm device, centered by means of a plumb bob or optical plummit over staton A, t

30、rasmits a carrier signal of electromagnetic energy upon which a reference frequency has been superimposed or modulated. The signal is returned from staion B to the revevier, so its trvel path is double the slope distance AB. In Fig.8-1,the modulated electromagnetic energy is represented by a series

31、of sine waves having wave-length . Any position along a givenj wave can be specified by its phase angle, which is 0°at its beginning, 180°at the midpoint, and 360°at its end.EDM devices used in surveying operate by measuring phase shift. In this procedure, the returned energy undergoe

32、s a complete 360°phase change for each even multiple of exactly one-half the wavelength separating the line-s endpoints. If, therefore, the distance is precisely equal to a full multiple of the half-wave-length, the indicated phase change will be zero. In Fig.8-1.for example, stations A and B a

33、re exactly eight half-wavelengths apart : hence, the phase change is zero. When a line is not exactly an even meltiple of the halfwavelength (the usual case , the fractional part is measured by the instrument as a nonzero phase angle or phase change. If the precise length of a wave is known, the fra

34、ctional part can be converted to distance.EDMIs directly resolve the fractional wavelength bu do not count the full cycles undergone by the returned energy in traveling its double path. This ambiguity is resolved, however, by transmetting additional signals of lower frequency and longer wavelengths.

35、中文翻譯水準尺和水準儀有許多類型的有價值的水準尺,一些是一體的,另一些(為了運輸?shù)陌踩词切璋惭b望遠鏡,要么是得安裝絞鏈,水準尺通常是由木材制成的,并且在底端刻度從零開始， 他們可以通過望遠鏡或者通過司尺員在尺上設(shè)置的覘標來直 接讀數(shù)。大多數(shù)水準尺既可以自讀又可以作為覘標水準尺。 在使用的幾種水準尺中有費拉德爾菲亞水準尺， 芝加哥水準尺和佛羅里達水 準尺， 費拉德爾菲亞水準尺由兩部分組成， 是最普通的一種。 它有一個后續(xù)部分， 其前面部分上可以滑動。讀數(shù)在 7-13 英尺之間時，后面部分不必延伸出來；讀 數(shù)在 7-13 英尺之間，則要延伸水準尺。當水準尺被延伸時，則被稱為高標尺。 菲亞水準尺

36、被分為英尺、十分之英尺、百分之讀尺（被尺子上黑白相間的交換的 條節(jié)劃分開） 。 芝加哥水準尺是 12 英尺，其刻度劃分與菲亞尺相同，但它由三個滑動的部 分組成。佛羅里達有 10 英尺長，刻度由紅、白條帶劃分，每一條帶有 0.1 英尺 寬。另外為了運輸方便也采用防水織物作的帶尺，這種帶尺的分劃與普通水準尺 的分劃方法是相同的，而且可以貼在普通木條上。一但工作完成，帶尺便可以重 新移動或若卷起，而木條則可以扔掉。測量員可以在 200-300 英尺之外通過望遠 鏡用戰(zhàn)標清晰地讀出各種水準尺的讀數(shù)。戰(zhàn)標是附加在標尺上很小的、紅白相間 的金屬卡。戰(zhàn)標上的游標可以讓司尺員讀到近 0.001 英尺。 如果司

37、尺員使用戰(zhàn)標讀數(shù)，且望遠鏡超過 7 英尺，顯然，司尺員這時無法進 行正常的讀數(shù)。因此，水準尺背面是從低端開始 7-13 英尺。戰(zhàn)標被安置在水準 尺前面，并且后面部分被拉起來以后，戰(zhàn)標移動一個刻度，以便讓司尺員在水準 尺前面讀數(shù)。 在安置水準儀前，觀測員應(yīng)該想到他應(yīng)該站在什么地方觀測。換句話說，他 應(yīng)該考慮到如何安置三角架的腿，以便他能舒服的站在腿的中間，測他所想的工 作。 三腳架應(yīng)安置在堅硬的、儀器不下沉的地面上，當然大多數(shù)都安置在松軟時 而下沉的地方。給儀器提供一些特殊的支持如林莊或平臺是必要的。三角架的腿 應(yīng)該合適地展開并調(diào)節(jié)以便使水平腳，螺旋下的底座能夠接近水平。觀冊員繞著 儀器將三腳架

38、每條腿伸長固定在地面上。在山上時，通常將一條腿安上山坡上， 兩條腿安在山坡下，更便于觀測。 通往調(diào)節(jié)三條腿尺可能使儀器整平。如果使用的是四個腳螺旋，望遠鏡要轉(zhuǎn) 到一對向相反方向轉(zhuǎn)動的腳螺旋上。通過向相反方向轉(zhuǎn)動兩個腳螺旋，水準氣泡 粗略對中，氣泡將向左手大拇指方向移動。接著，望遠鏡轉(zhuǎn)向另一對相對的腳螺 旋，水準氣泡又一次粗略的對中。這個過程要小心的重復(fù)幾次，直到望遠鏡轉(zhuǎn)到 任意一對腳螺旋的方向氣泡都對中。如果水準儀整平了，那么望遠鏡轉(zhuǎn)到任一方 向時，氣泡應(yīng)保持對中。我們期望儀器輕微移動時，氣泡也輕微的移動。無論如 何，如果每次讀數(shù)時氣泡都居中，觀測的精度不應(yīng)該有不利的影響。 在整平三角架腳螺旋

39、時，第一步轉(zhuǎn)動望遠鏡，向相反方向調(diào)節(jié)兩個腳螺旋。 接下來轉(zhuǎn)動望遠鏡，以使水準管垂直于腳螺旋 1 和 2，調(diào)節(jié)使其居中，重復(fù) 這些步驟，直到望遠鏡來回轉(zhuǎn)動時氣泡保持居中。 電子測距儀 近年來，測量中的主要進步是電子測距儀的發(fā)展，當已知波長的電波能從一 條邊的一端傳播一另一端并返回時就發(fā)生了相變， 這些裝置就是根據(jù)這些來測定 長度的。 最早介紹電子測距儀的確 1984 年瑞典的物理學家 Erik Bergstrand,他的裝置， 命名為光電測距儀（gecdetic distance meter 的首字母縮寫） ，結(jié)果導致從實驗到 改進測量光速的方法。在晚上，儀器傳送可見，并且可精確 40km 的距離。1957 年，第二代 EDM 儀器產(chǎn)生，微波測距儀由 D.K 博士發(fā)明并介紹到南非，傳送不 可見的微波可全天觀測，距離在 80km 以上。 這些早期的 EDM 模型對測量專業(yè)的潛在價值立即被人們認可，盡管他們是 昂貴的，甚至在里子外操作是不輕便的，并且測量的過程是冗長的，而且從數(shù)據(jù) 中獲取有用