computations, are simply reduced by 360° before final listing. Bearing is the traditional way of stating the orientation of the line. 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 trending 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.
现代的电子数字经纬仪包含编码度盘，能够感知轴和望远镜的旋转，并使之电子地转换为水平角度和竖直角度，并在液晶显示器或发光二极管显示器上显示出来，这些显示可以被一个传统的野外电子手簿或数据收集器记录，以便日后打印或计算。这种仪器具有一个悬挂补偿器或其它装置，使竖盘指标读数指向一个绝对竖直方向，这个度盘可以通过简单的按一个键就将其置零，或初始化成任一值。方位角是从子午面起算按顺时针旋转的角，子午线是在地球平均表面连接北极与南极的线。方位角的取值范围从0度到360度，超过360的值――有时会在计算时遇到，只需减去360度即可。方向角是一种传统的描述直线方向的方法。实际上，它是从南或北方向开始量测的角，方向角可以从子午线，北端或南端以顺时针或逆时针量测，总是伴以字母，用来标明直线所落在的象限。方向角N32W代表一条直线从北方向转向西方向32度，它等于方位角328度，方向角S12W代表一条直线从南方向转向西方向12度，它等于方位角192度。需要重点说明的是，方向角和方位角所用的是真北方向。
Unit 5 Traversing （导线测量）
The purpose of the surveying is to locate the positions of points on or near the surface of the earth.（测量的目的是确定地表或接近地表的点的点位。）
To determine horizontal positions of arbitrary points on the earth’s surface and elevation of points above or below a reference surface are known as a control survey.（确定地表任一【arbitrary任意的】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）
The positions and elevations of the points make up a control network.（这些点的平面位置和高程组成了一个控制网）
There are different types of control networks depending on where and why they are established.（依照它们建立的地点和目的不同，有不同的控制网类型）
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位置（称为高程控制网））
Some points in a control network have both accurate positions and elevations.（有些控制网的点既有精确的平面位置也有精确的高程）
Control networks range from small, simple and inexpensive to large and complex and very expensive to establish.（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）
A control network may cover a small area by using a “local” coordinate system that allows you to position the features in relation to the control network but doesn’t 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 primary control.（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【feature】，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）
The horizontal positions of points in a network can be obtained in a number of different ways.（控制网的点的平面位置可以由许多不同方法来获得）
The generally used methods are triangulation, trilateration, traversing, intersection, resection and GPS.（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） The main topic of this text refers to the traversing.（这篇课文主要讲的是导线测量） Triangulation（三角测量）
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 computed by the law of sines.（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）
Furthermore, if the direction of one side is known, the direction of the remaining sides can be determined.（而且，如果一条边的方向已知，余下的边的方向也可以确定）
And then coordinates of unknown points can be computed by application of trigonometry.（那么未知点的坐标就可以使用三角法计算出来）
Trilateration（三边测量）
Since the advent of long-range EDM instrument, a method of surveying called trilateration was adopted to combine with triangulation.（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。）
The trilateration is based on the trigonometric proposition that if the three sides of a triangle are known, the three angles can be computed by the law of cosines.（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）
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 triangulation may be more difficult and expensive.（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）
For some precise projects, the combination of triangulation and trilateration which is called triangulateration is applied.（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）
Traversing（导线测量）
A survey traverse is a sequence of lengths and directions of lines between points on the earth, obtained by or from field angle and distance measurements and used in determining positions of the point.（导线是一系列地球上点之间的有长度和方向的直线，由野外角度和距离测量获得，用来确定点位）
The angles are measured using transits, theodolites, or total stations, whereas the distances can be measured using steel tapes or EDM instruments.（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）
A survey traverse may determine the relative positions of the points that if connects in series, and if tied to control stations based on some coordinate system, the positions may be referred to that system.（导线可以用来确定互相连接点的相对位置，如果想控制某些坐标系中的站点，其位置应参考该坐标系）
From these computed relative positions, additional data can be measured for layout of new features, such as buildings and roads.（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。）
Since the advent of EDM equipment, traversing has emerged as the most popular method to establish control networks such as basic area control, mapping, control of hydrographic surveys and construction projects.（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）
In engineering surveying, it is ideal way to surveys and dimensional control of route-type projects such as highway, railroad, and pipeline construction. （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）
In general, a traverse is always classified as either an open traverse or a closed traverse.（总体上，导线总是分为支导线和闭路导线【按说open traverse是支导线，closed traverse是闭合导线，而connecting traverse是附合导线】）
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 whose relative position is not previously known.（支导线起始于一个水平位置已知（相对于一个水平基准）或水平位置假定的点，终止于相对位置事先未知的站点。）
The open traverse provides no check against mistakes and large errors for its termination at an unknown horizontal position and lack of geometric closure.（由于其终点位置未知并且缺乏图形闭合，支导线不能提供对错误和较大误差的检核）
This lack of geometric closure means that there is no geometric verification possible with respect to the actual positioning of the traverse stations.（这种图形闭合的缺少意味着没有几何上的检核可能性，对于实际的导线点的确定。）
Thus, the measuring technique must be refined to provide for field verification.（因而，这种测量技术应当提供野外的检核使之精确。）【字面的意思是该技术应当被精确化提供给野外确认】 At a minimum, distances are measured twice and angles are doubled.（至少，距离测两遍，角度测两个测回。）
Open traverses are often used for preliminary survey for a road or railroad.（支导线经常用于道路或铁路的初测）
A closed traverse can be described in any one of the following two ways:（闭路导线可以由下面两种方式的任一种描述：）
⑴A closed loop traverse, as the name implies, forms a continuous loop, enclosing an area. （闭合环路导线，正如名字所示，呈一个连续的环，围绕一个区域）
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.（这种闭路导线起始于一个平面位置假设或相对于一个水平基准已知的点，并终止于该点）
⑵A connecting traverse starts and ends at separate points, whose relative positions have been determined by a survey of equal or higher order accuracy.（附合导线起始和终止于不同的点，它们由等于或高于规定精度的测量测设）
A known horizontal position is defined by its geographic latitude and longitude, or by its X and Y coordinates on a grid system.（一个已知的水平位置是由它的大地经纬度或格网系的X Y坐标表示） Closed traverses, whether they return to the starting point or not, provide checks on the measured angles and distances.（闭合导线，无论它们是否回到起始点，都能提供角度和距离检核。）
In both cases, the angles can be closed geometrically, and the position closure can be determined mathematically.（在两种情况中，角度可以在几何上闭合，位置闭合可以数学的确定【计算出来】） Therefore they are more desirable and used extensively in control, construction, property, and topographic surveys. （因此它们更理想【desirable理想的】，在控制测量、建筑测量、房地产测量和
地形测量使用更广泛）
As we mentioned above, a closed traverse provides checks on the measured angles and distances.（正如我们上面所提到的，闭合导线可以提供角度和距离的检核）
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, 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.（例如，在一个n边闭合图形当中，内角和应该是：(n-2)×180°，但是由于【due to】测量中系统误差和偶然误差的存在，当闭合导线所有的内角加起来后，其角度和【total】可能等于或不等于其几何理论闭合差值）
The difference between the geometric sum and actual field sum of the interior angles is called angular closure.（内角和的理论值和实际值的差值被称为角度闭合差）
The total error of angular closure should be distributed evenly to each angle (if all angles were measured with the same precision) before mathematical analysis of the traverse.（在导线进行数学分析之前，角度闭合差应该平均分配到每个角上（如果所有的角都是相同观测精度））
The important point before doing this is that the overall angular closure can’t be beyond the survey specifications.（重要的一点是，在这样做之前，所有的闭合差都不得超过测量规范）
Closed traverses provide also checks on the measured 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.（闭合导线同时提供测量过的距离的检核，位置的闭合差可以计算得到，这就意味着测量的距离同测角一样，应当予以闭合
Theoretically this position closure from the origin back to itself should be zero.（理论上，从起点闭合到它自己，位置的闭合差应该是0）
But 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 from the origin to the closing point.（但是距离和角度的测量误差，会改变【alter】导线的形状，因此我们应当分别计算纵距与横距的代数和，然后与从起点到终点的连线的确定的纵距与横距相比较）
By definition, latitude here is the north/south rectangular component of a line and departure is the east/west rectangular component of a line.（精确的说，这里的纵距就是指一条直线的直角坐标的南北分量，横距就是指一条直线的直角坐标的东西分量）
To differentiate direction, north is considered plus, whereas south is considered minus. （对于不同的方向来说，北方向为正，南方向为负）
Similarly, east is considered plus, whereas west is considered minus.（同样的，东为正，西为负） Then the discrepancy should be adjusted by apportioning the closure both in latitudes and in departures on a reasonable basis.（然后差值应以合理的原则进行调整分配闭合差到纵距和横距上去） The adjusted position of each traverse point is determined with respect to some origin.（ This position is defined by its Y coordinates and 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.（其位置由平面直角坐标系的Y坐标和X坐标来定义，Y轴代表南北方向，而【whereas反之】X轴代表东西方向）
Unit 6 Methods of Elevation Determination（高程测量方法）
An elevation is a vertical distance above or below a reference datum.（高程是高于或低于一个参考基准的一个垂直距离。）
Although vertical distance can be referenced to any datum, in surveying, the reference datum that is universally employed is that of mean sea level (MSL).（虽然垂直距离可以参考任何一个基准，但是在测量上，这个参考基准一般使用的是平均海平面（MSL））
MSL is assigned a vertical value (elevation) of 0.000 ft or 0.000 m.（MSL被赋予一个0.000英尺或0.000米的高程）
All other points on the earth can be described by the elevations above or below zero.（地球上所有其它点可以用高于或低于0的高程来描述）
Permanent points whose elevations have been precisely determined (benchmarks) are available in most areas for survey use.（高程精确测出的永久点（水准点）被用于大多数区域的测量工作） In China, 7 years of observations at tidal stations in Qingdao from 1950 to 1956 were reduced and adjusted to provide the Huanghai vertical datum of 1956.（在中国，利用青岛验潮站从1950年到1956年7年的观测数据处理和平差，建立了56黄海高程系统）
In the 1987, this datum was further refined to reflect long periodical ocean tide change to provide a new national vertical datum of 1985, according to the observations at tidal stations from 1952 to 1979.（1987年，在依照了验潮站1952到1979年的观测资料后，这个基准被进一步精确——反映长时期海潮变化的85国家高程基准建立起来。）
Although, strictly speaking, the national vertical datum may not precisely agree with the MSL at specific points on the earth’s surface, the term MSL is generally used to describe the datum.（虽然，严格说来，国家高程基准在特殊的点上与MSL并不恰好吻合，术语MSL一般还是用来描述它） MSL is assigned a vertical value (elevation) of 0.000 ft or 0.000 m.（MSL高程的赋值为0.000英尺或米）
Difference in elevation may be measured by the following methods:(James M. Anderson and Edward M. Mikhail. 1998)（高程的差异可以由下列方法测得（詹姆斯.安德森和爱德华.？？？））
1. Direct or spirit leveling, by measuring vertical distances directly.（水准测量，直接测得垂直距离）
Direct leveling is most precise method of determining elevations and the one commonly used.（水准测量是高程测量方法中精度最高、使用最普遍的方法）
2. Indirect or trigonometric leveling, by measuring vertical angles and horizontal or slope distances.（三角高程测量，利用测量竖直角和水平或斜距来测高程）
3. Stadia leveling, in which vertical distances are determined by tacheometry using engineer’s transit and level rod; plane-table and alidade and level rod; or self-reducing tacheometer and level rod.（视距高程测量，利用视距测量，使用工程经纬仪和水准尺；平板仪和照准仪和水准尺；或者自处理视距仪和水准尺测得垂直距离）
4. Barometric leveling, by measuring the differences in atmospheric pressure at various stations by means of a barometer.（气压水准测量，通过使用气压计测量不同站点大气压力的差值来测高程） 5. Gravimetric leveling, by measuring the differences in gravity at various stations by means of a gravimeter for geodetic purposes.（重力水准测量，通过使用重力计测量不同站点的重力值差值来测高程，用于大地测量学的目的）
6. Inertial positioning system, in which an inertial platform has tree mutually perpendicular axes, one of which is “up”, so that the system yields elevation as one of the outputs.（惯性定位系统，含有一个惯性平台，具有三个互相垂直轴，其中一个是“向上”的，所以这个系统产生的输