highway survey method

英译汉

Highway Survey Methods

Highway surveys usually involve measuring and computing horizontal and vertical angles, vertical heights (elevations), and horizontal distances. The surveys are then used to prepare base maps with contour lines (that is, lines on a map connecting points that have the same elevation) and longitudinal cross-sections. Highway surveying techniques have been revolutionized due to the rapid development of electronic equipment and computers. Surveying techniques can be grouped into three general categories: ground surveys, remote sensing and computer graphics.

公路勘测通常包括测量和计算水平角，垂直角，垂直高度（海拔高度）和水平距离。然后测量数据被用来准备并绘制含有等高线（即地形图上高程相等的连结点组成的闭合曲线）和纵向截面的基本图。由于电子设备和计算机的快速发展，公路勘测技术有了革命性的发展。测量技术可以被分为三大类：地面勘测，遥感和计算机绘图。

1.Ground surveys

Ground surveys are the basic location technique for highways. The total station is used for measuring angles in both vertical and horizontal planes, distances, and changes in elevation through the use of trigonometric levels; the level is used for measuring changes in elevation only. A summary of survey equipment follows.

地面测量是基本的道路选址技术。使用全站仪测量斜面与平面的角度、测量距离以及使用三角函数得到高度的变化。此函数只能用于测量高度的变化。以下为勘测仪器的总结。

1.1 The Total Station

A total station is both an electronic theodolite and electronic distance-measuring device (EDM). The total station enables one to determine angles and distances from the instrument to other points. Angles and distances may be used to calculate the actual positions (coordinates and elevations).

一台全站仪既是电子经纬仪又是电子测距装置。它可以使人们能够从仪器到另一点确定角度和距离，角度和距离可以用来计算实际的位置（坐标和高程）。

The standard theodolite consist of a telescope with vertical and horizontal cross hairs, a graduated arc or vernier for reading vertical angles, and a graduated circular plate for reading horizontal angles, whereas the electronic theodolite provides a digital readout of those angles. These readouts are continuous, so angles can be checked at any time. The telescope on both instruments is mounted so that it can rotate vertically about a horizontal axis. With the standard theodolite, two vertical arms support the telescope on its horizontal axis, with the graduated arc attached to one of the arms. The arms are attached to a circular plate, which can rotate horizontally with reference to the graduated circular plate, thereby providing a means for measuring horizontal angles.

标准的经纬仪由一个配有竖直和水平制动螺旋的望远镜，一个竖直度盘（刻度弧或游标），以及一个圆形水平度盘。而电子经纬仪则提供角度的电子读数，并且能持续读数以便随时查看角度值。二者都配有悬挂着的望远镜以便其能绕着横轴竖直转动。标准经纬仪两个竖直臂将望远镜支撑于其水平轴上，其中一竖直臂装有刻度弧。两个竖直臂连接在一个能够根据圆形刻度盘水平转动的基座圆盘上，以此测量水平角。

1.2 Electronic Distance-Measuring Devices (EDM)

An EDM device consists mainly of a transmitter located at one end of the distance to be measured and a reflector at the other end. The transmitter sends a light beam or a low-power laser pulse which is reflected back to the transmitter. The difference in phase between the transmitted and reflected pulses is measured electronically and used to determine the distance between the transmitter and the reflector. This equipment can measure distances up to about 1,000 meters in average atmospheric conditions. Special features permit the operator to change the display from slope to horizontal distance automatically. Units can also be changed from meters to feet. The total station offers these solutions because of internal instantaneous calculations.

1.2 电子测距仪（EDM）

电子测距仪主要是由一个位于测量距离一端的发射器和另一端的反射器组成。发射器发射一个光束或低功率激光脉冲，然后被反射回来。发射和反射的脉冲相位差就会被电子测量，并用来确定发射器和反射器之间的距离。该设备可测量的距离能达到平均大气条件下约1000米。其特殊的功能可以允许操作者自动改变显示器从斜坡到水平的距离。距离单位也可以从米变化到英尺。全站仪之所以能够提供这些功能，是因为其内部的瞬时计算。（张晗，龙飞宇）

Figure 1 Illustration of Horizontal Angle

Measurement of Horizontal Angles. A horizontal angle, such as angle XOY in Figure 1, can be measured by setting the theodolite or total station directly over the point O. The telescope is then turned toward point X and viewed first over its top and then by sighting through the telescope to obtain a sightline of OX, using the horizontal tangent screws provided. The graduated horizontal scale is then set to zero and locked into position, using the clamp screws provided. The telescope is rotated in

the horizontal plane until the line of sight is OY. The horizontal angle (α) is read from the graduated scale. While similar in method to theodolite, when using a total station, the angle measured is shown in a digital readout when a horizontal readout is selected.

水平角度的测量。测量一个像图1中XOY一样的水平角度可以通过设置一个经纬仪或者全站仪在O点上，把望远镜调到对准X点的位置并且首先在它的顶端观察，然后从望远镜里观测并且通过使用水平切线螺旋获得一条OX视线。水平角度值α就显现在了累进刻度上。使用全站仪的方法与此类似，当使用一台全站仪的时候，固定好水平读出器，测量的角度值会显现在一个读数器上。

Figure 2 Illustration of Vertical Angle

Measurement of Vertical Angles. The theodolite measures vertical angles, such as angle AOB in Figure 2 by using the fixed vertical graduated arc or vernier and a spirit level attached to the telescope. When a theodolite is used to determine the vertical angle to a point, the angle (β) obtained is the angle of elevation or the angle of depression from the horizontal. The theodolite is set up in a way similar to that for measuring horizontal angles, ensuring that the longitudinal axis is in the horizontal position. The telescope is approximately sighted at the point. The tangent screw of the telescope is then used to set the horizontal cross hair at the point. The vertical angle is obtained from the graduated arc or the vertical vernier. Again, while similar in method to a theodolite , when using a total station, the angle measured is shown in a digital readout when a vertical readout is selected.

竖直角的测量。

经纬仪测量竖直角，例如使用固定的垂直分度弧(竖盘)或者游标尺和望远镜上的水准器测量图2中的角AOB。当使用经纬仪观测一个目标点确定竖直角，角（&）包括仰角和俯角。经纬仪的放置方法和测量水平角时相似，确保纵轴在一水平方位，望远镜大致对准目标点，然后调节望远镜上的微动螺旋使十字丝对准目标点。竖直角从分度弧或垂直游标上获得。另外，与经纬仪类似，当使用全站仪时，选择一个垂直读数，测得的角度将显示在数字读出仪上。

1.3 The Level

The essential parts of a level are the telescope, with vertical and horizontal cross hairs, a level bar, a spindle, and a leveling head. The level bar on which the telescope is mounted is rigidly fixed to the spindle. The level tube is attached to the telescope or the level bar so that it is parallel to the telescope. The spindle is fitted into the leveling head in such a way that allows the level to rotate about the spindle as an axis, with the leveling head attached to a tripod. The level also carries a bubble that indicates

whether the level is properly centered. The centering of the bubble is done by using the leveling screws provided.

2.Remote Sensing

Remote sensing is the measurement of distance and elevations by using devices located above the earth, such as airplanes or orbiting satellites using Global Positioning Satellite systems (GPS). The most commonly used remote-sensing method is photogrammetry, which utilizes aerial photography. Photogrammetry is the science of obtaining accurate and reliable information through measurements and interpretation of photographs, displaying this information in digital form and/or map form. This process is fast and economical for large projects but can be very expensive for small projects. The break-even size for which photogrammetry can be used varies between 30 and 100 acres, depending on the circumstances of the specific project. The successful use of the method depends on the type of terrain. Difficulties will arise when it is used for terrain with the following characteristics.

●Areas of thick forest, such as tropical rain forests, that completely cover the

ground surface

●Areas that contain deep canyons or tall buildings, which may conceal the ground

surface on the photographs.

●Areas that photograph as uniform shades, such as plains and some deserts

The most common uses of photogrammetry in highway engineering are the identification of suitable locations for highways, referred to as corridor study, and the preparation of base maps for design mapping, showing all physical and man-made features plus contours of 2- or 5-ft intervals. In both of these uses, the first task is to obtain the aerial photographs of the area if none is available.

https://www.wendangku.net/doc/5813223931.html,puter Graphics

Computer graphics, when used for highway location, is usually the combination of photogrammetry and computer techniques. With the use of mapping software, line styles, and feature tables, objects and photographic features can be recorded digitally and stored in a computer file. This file can then either be plotted out in map form or sent on to the design unit. A typical workstation is controlled by system software that covers four main areas of design work:

●Preparatory work (project setup)

●Photo orientations and aerotriangulation

●Data transfer

●Plotting and storage

The software for preparatory work is used for the input of control point coordinates, input of camera calibration data, and the selection of the needed image files. The aerotriangulation software is used for automatically locating fiducial marks (interior orientation), the removal of bad parallax (relative orientation), scaling and leveling the images (absolute orientation), and the creation of a control mesh. The

data transfer programs store and check all data in digital form in a MicroStation file for use by designers. The fourth area is that of file storage and plotting.