中英文互译文章

1、Traversing结构工程：徐传枝 2009040223The purpose of the surveying is to locate the positions of points on or near the surface of the earth. To determine horizontal positions of arbitrary points on the earths surface and elevation of points above or below a reference surface are known as a control survey. Th

2、e positions and elevations of the points make up a control network. There are different types of control networks depending on where and why they are established. A control network may have very accurate positions but no elevations (called a Horizontal Control Network) or very accurate elevations bu

3、t no positions (called a Vertical Control Network). Some points in a control network have both accurate positions and elevations. Control networks range from small, simple and inexpensive to large and complex and very expensive to establish. A control network may cover a small area by using a “local

4、” 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 prima

5、ry control. The horizontal positions of points in a network can be obtained in a number of different ways. The generally used methods are triangulation, trilateration, traversing, intersection, resection and GPS. The main topic of this text refers to the traversing.TriangulationThe method of surveyi

6、ng 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 computed by the law of sines. Furthermore, if the direction of one side is known, the direction of the remaining sides can be determined. And then c

7、oordinates of unknown points can be computed by application of trigonometry.Trilateration Since the advent of long-range EDM instrument, a method of surveying called trilateration was adopted to combine with triangulation. The trilateration is based on the trigonometric proposition that if the three

8、 sides of a triangle are known, the three angles can be computed by the law of cosines. Trilateration possesses some advantages over triangulation because the measurement of the distances with EDM instrument is so quick, precise and economical while the measurement of the angles needed for triangula

9、tion may be more difficult and expensive. For some precise projects, the combination of triangulation and trilateration which is called triangulateration is applied.TraversingA survey traverse is a sequence of lengths and directions of lines between points on the earth, obtained by or from field ang

10、le and distance measurements and used in determining positions of the point. The angles are measured using transits, theodolites, or total stations, whereas the distances can be measured using steel tapes or EDM instruments. A survey traverse may determine the relative positions of the points that i

11、f connects in series, and if tied to control stations based on some coordinate system, the positions may be referred to that system. From these computed relative positions, additional data can be measured for layout of new features, such as buildings and roads. Since the advent of EDM equipment, tra

12、versing has emerged as the most popular method to establish control networks such as basic area control, mapping, control of hydrographic surveys and construction projects. In engineering surveying, it is ideal way to surveys and dimensional control of route-type projects such as highway, railroad,

13、and pipeline construction. In general, a traverse is always classified as either an open traverse or a closed traverse. An open traverse originates either at a point of known horizontal position with respect to a horizontal datum or at an assumed horizontal position, and terminates at a station whos

14、e relative position is not previously known. The open traverse provides no check against mistakes and large errors for its termination at an unknown horizontal position and lack of geometric closure. This lack of geometric closure means that there is no geometric verification possible with respect t

15、o the actual positioning of the traverse stations. Thus, the measuring technique must be refined to provide for field verification. At a minimum, distances are measured twice and angles are doubled. Open traverses are often used for preliminary survey for a road or railroad. A closed traverse can be

16、 described in any one of the following two ways: A closed loop traverse, as the name implies, forms a continuous loop, enclosing an area This type of closed traverse starts at assumed horizontal position or at a known horizontal position with respect to a horizontal datum and ends at the same point.

17、 A connecting traverse starts and ends at separate points, whose relative positions have been determined by a survey of equal or higher order accuracy. A known horizontal position is defined by its geographic latitude and longitude, or by its X and Y coordinates on a grid system. Closed traverses, w

18、hether they return to the starting point or not, provide checks on the measured angles and distances. In both cases, the angles can be closed geometrically, and the position closure can be determined mathematically. Therefore they are more desirable and used extensively in control, construction, pro

19、perty, and topographic surveys. As we mentioned above, a closed traverse provides checks on the measured angles and distances. For example, the geometric sum of the interior angles in an n-side closed figure should be (n-2)×180°, but due to systematic and random errors of the measurements,

20、 when all the interior angles of a closed traverse are summed, they may or may not total the number of degrees required for geometric closure. The difference between the geometric sum and actual field sum of the interior angles is called angular closure. The total error of angular closure should be

21、distributed evenly to each angle (if all angles were measured with the same precision) before mathematical analysis of the traverse. The important point before doing this is that the overall angular closure cant be beyond the survey specifications. Closed traverses provide also checks on the measure

22、d distances, and the position closure can be determined mathematically, which means that an indication of the consistency of measuring distances as well as angles should be given to a traverse that closes on itself. Theoretically this position closure from the origin back to itself should be zero. B

23、ut the Errors in the measured distances and angles of the traverses, however, will tend to alter the shape of the traverse, therefore we should compute the algebraic sum of the latitudes and algebraic sum of the departures, and compare them with the fixed latitude and departure of a straight line fr

24、om the origin to the closing point. By definition, latitude here is the north/south rectangular component of a line and departure is the east/west rectangular component of a line. To differentiate direction, north is considered plus, whereas south is considered minus. Similarly, east is considered p

25、lus, whereas west is considered minus. Then the discrepancy should be adjusted by apportioning the closure both in latitudes and in departures on a reasonable basis. The adjusted position of each traverse point is determined with respect to some origin.This position is defined by its Y coordinates a

26、nd its X coordinates with respect to a plane rectangular coordinate system in which the Y axis is assumed north-south whereas the X axis east-west.导线测量测量的目的是确定地表或接近地表的点的点位。确定地表任一点的平面位置和确定点高于或低于一个参考面的高程的工作被称为控制测量。这些点的平面位置和高程组成了一个控制网。依照它们建立的地点和目的不同，有不同的控制网类型。一个控制网可能有精确的平面位置而没有高程（称为平面控制网），或者有精确的高程而没有平面

27、位置（称为高程控制网）。有些控制网的点既有精确的平面位置也有精确的高程。控制网的范围从小的、简单的、便宜的网到大的、复杂的、昂贵的网。一个控制网可以是覆盖小范围，使用区域坐标系统，允许你相对于控制网确定地貌特征，但却不告诉你它们在地表的什么地方；或者覆盖一个广大区域，由少数被适当安置并精确测设的控制点组成，有时被称为基础控制。控制网的点的平面位置可以由许多不同方法来获得。一般使用的方法有，三角测量、三边测量、导线测量、交会测量、后方交会测量、和GPS测量。这篇课文主要讲的是导线测量三角测量这种测量方法称为三角测量，基于三角法则，如果三角形的一条边和三个角已知，剩下的边可以用正弦定理计算出。而且

28、，如果一条边的方向已知，余下的边的方向也可以确定，那么未知点的坐标就可以使用三角法计算出来。自从远距EDM出现以来，一种叫做三边测量的方法用来和三角测量联合使用。三边测量基于三角法则如果三角形的三条边已知，那么三个角可以由余弦定理计算出。三边测量具有一些相对于三角测量的优势，EDM测距快速、准确、经济，而三角测量所需的角度测量则相对困难和昂贵。在一些精密工程当中，三角测量和三边测量联合使用，被称为边角测量。导线测量测量工作中的导线是一系列地球上点之间的有长度和方向的直线，导线由野外角度和距离测量获得，用来确定点位。角度可以使用经纬仪或全站仪来测，而距离可以使用卷尺或EDM来测。导线可以用来确定

29、互相连接点的相对位置，如果想控制某些坐标系中的站点（以某坐标系的点为站点），其位置应参考该坐标系，从这些计算出的相对位置，另外的数据可以量出来，用以放样新的地物，如：建筑物和道路。自从EDM的出现，导线测量作为最常用的建立控制网的方法显现出来，例如基础区域控制、图根控制、水道测量控制和建筑工程控制（建筑施工控制）。在工程测量当中，导线测量是线型工程测量和立体控制的理想方法，线型工程例如公路、铁路、和管线建筑。总体上，导线总是分为支导线和闭路导线，支导线起始于一个水平位置已知（相对于一个水平基准（水平坐标系）或水平位置假定的点，终止于相对位置事先未知的站点）。由于其终点位置未知并且缺乏图形闭合，支导线