Topographic Surveying.doc

Topographic Surveying 地形测量General The distinguishing feature of a topographic survey is the determination of the location, both in plan and elevation, of selected ground points which are necessary for plotting contour lines and the planimetric location of features on the topographic map. A topographic survey consists of (1) establishing over the area to be mapped a system of horizontal and vertical control, which consists of key stations connected by measurements of high precision; and (2) locating the details, including selected ground points, by measurements of lower precision from the control stations.通常，地形测量就是反应地物地貌的特征，测定地物地貌的平面位置和高程，测定绘制等高线所必需的地面点，绘制到地形图上。地形测量包括(1)在目标地区建立由大地控制点为基础的高精度平面控制和高程控制系统；(2)以及碎部测量，通过选择并测定反映地物地貌的低精度碎部点组成。Topographic surveys can be performed by aerial photogrammetric methods, by ground survey methods, or by some combination of these two procedures. Almost all of the small and intermediate scale as well as some large-scale topographic mapping is now performed by photogrammetric methods. This photogrammetric operation includes establishing portions of the horizontal control in addition to compilation of the topographic map. However, ground survey methods are still applicable for large-scale topographic mapping of small areas and for field completion surveys which are usually needed for photogrammetrically compiled topographic maps. The discussions in this lesson are directed primarily toward the various procedures for topographic surveys by ground survey methods.地形测量可以通过使用航空摄影测量的方法，或者通过大地测量的方法，以及以上两种方式相结合的方法完成。几乎所有小区域和中型区域大比例尺的地形图测绘一样，现在采用摄影测量的形式完成。摄影测量包括建立联系一部分水平控制来完成地形的的测绘编辑工作。然而，大地测量的方法仍然适用于小区域的大比例尺地形图测量，野外检测通常也需要摄影测量来补充完善地形测量工作。本文中的内容是讨论关于用大地测量来完成地形测量工作所需要的各种程序和步骤。Establishment of control The first requirement of any topographic survey is good control, whether the survey is done by ground or aerial methods. Control consists of two parts: (1) horizontal control, in which the planimetric positions of specified control points are located by trilateration, triangulation, intersection, resection, or traverse; and (2) vertical control, in which elevations are established on specified bench marks located throughout the area to be mapped. This control provides the skeleton, which is later clothed with the details, or locations of such objects as roads, houses, trees, streams, ground points of known elevations, and contours.建立控制 进行任何形式的地形测量无论是大地测量还是航空摄影测量都需要建立高精度的控制网。控制包括两个部分:(1)平面控制,通过三边测量,三角测量,侧方交会，后方交会,或导线测量确定平面指定控制点的位置；(2)高程控制，建立确定贯穿于被测量地区的特定水准点的高程。控制测量为以后的碎部测量工作，像公路、房屋、树木、溪流、已知地面点高程和等高线测定提供了依据和参照。On surveys of wide extent, a relatively few stations distributed over the tract are connected by more precise measurements, forming the primary control; within this system, other control stations are located by less precise measurements, forming the secondary control. For small areas only one control system is necessary.测量过程中，在大面积的测区范围内建立相对分布均匀的，精度高的测量工作形成首级控制。在首级控制网下，建立精度较低的控制点形成图根控制点。对于小规模的测绘工作，只需要建立图根控制系统。Horizontal controlHorizontal control can be established by triangulation, trilateration, traverse, aerial photogrammetric methods, inertial and doppler positioning systems, and the global positioning system.平面控制 平面控制可以通过三角测量，三边测量，导线测量，航空摄影测量，惯性和多普勒系统，全球定位系统建立完成。Triangulation and trilateration can be used to establish primary and secondary control for relatively large topographic surveys. These methods are also utilized in areas of lesser extent when field conditions are appropriate (hilly, urban, or rugged mountainous regions).三角测量和三边测量可以用来为大面积范围内的地形测量建立首级控制网和图根控制网。这些方法也适用于小范围的外业（丘陵，城市，崎岖的山区）测量。Traverse with a theodolite and electronic distance measurement (EDM) instrument can also be used for primary and secondary control surveys.首级控制和图根控制网是通过使用经纬仪，电子测距仪的导线测量来完成的。Horizontal control determination by aerial photogrammetric methods is feasible and particularly applicable to small-scale mapping of large areas. Note that this procedure requires a basic framework of horizontal control points established by traditional methods (trilateration and/or triangulation) or by inertial, doppler, or global positioning systems.平面控制测定通过摄影测量的方法是可行的，并且适用于大面积区域的小比例尺地形图测绘。记录这个程序，需要通过一个传统方法（三边测量或者三角测量）或者惯性测量，多普勒效应测量，全球定位系统建立平面控制点网。Inertial, doppler, and global positioning systems are most appropriate for establishing primary horizontal control when the topographic survey is of very large extent, covers an inaccessible region, or where the conduct of the survey is governed by special conditions.惯性测量，多普勒效应测量，全球定位系统适用于在大面积的地形测量中，难以到达的地区或者要进行特殊方法测量的情况下建立首级控制。Vertical control The purpose of vertical control is to establish bench marks at convenient intervals over the area to serve as (1) points of departure and closure for leveling operations of the topographic parties when locating details, and (2) reference marks during subsequent construction work.高程控制 高程控制的目的就是在测区内建立方便，均匀的水准基点来作为（1）碎部测量中定位碎部点的位置和高程（2）和作为随后建设施工工程的参考标准。Vertical control is usually accomplished by direct differential leveling, but for small areas or in rough country the vertical control is frequently established by trigonometric leveling. 高程控制通常由微差水准测量完成，在崎岖的乡下地区高程控制经常由三角高程测量完成。All elevations for topographic mapping should be tied to bench marks which are referred to the mean sea level.所有地形测绘水准基点的高程应该以大地水准面作为参考面。Details by the controlling-point method Details may be located by the controlling-point method employing the transit and stadia, the plane table and alidade, or electronic systems. This method is applicable to practically every type of terrain and condition encountered in topographic mapping. Since only the controlling points that govern the configuration of the land and location of details are located, a measure of economy is achieved that is not possible in the other techniques. However, the topographer must be experienced的since the success of the method depends on selection of the key controlling points. 依据控制点进行碎部点定位时常使用子午仪，视距仪，平板仪，照准仪或者电子控制系统。这些方法几乎适合于地形测量中遇到的所有地形和环境条件。自从只有控制点支配碎部点的分配和结构，测量技术的经济性方面取得了其他技术不曾有的成就。然而，自从这些方法的成功依靠关键控制点的选择后，地质工作者必须拥有相当丰富的经验。The personnel of the topography party using the transit usually consists of an instrument operator, a notekeeper, and one or two people operating the rods. 一个地形测量小组通常由一个仪器操作者，一个记录人员，和一到两个立尺人员组成。In locating ground points, the vertical angles are measured more precisely than the horizontal angles. Accordingly, the vertical circle of the instrument assumes greater importance than the horizontal circle; but because the vertical angles are measured with respect to a horizontal plane, it is important that the horizontal plate be truly horizontal and remain so without need for constant releveling. In this respect, the modern optical repeating theodolites with automatic selfindexing of the vertical circle are a definite的asset in this type of work.在定位地面点时，竖直角的测量精度比水平角的测量精度更高。因此，仪器的竖直度盘比水平度盘重要。但是由于竖直角是测量在竖直面上的投影，水平盘必须是绝对的水平，不需要重复精平是非常重要的。在这方面，现代自动指标的光学复测经纬仪的竖直度盘在这种类型的工作中具有明确的优势。The transit is set up on either a primary or secondary control station, the elevation and position of which are known. The height of instrument (h.i.) of the horizontal axis of the instrument above the station over which it is set is measured with a rod or tape. The vertical circle is checked for index error and the transit is oriented by backsighting along a line the azimuth of which is known, this azimuth having been set off on the clockwise horizontal circle. The upper motion is unclamped and sights to the desired points are taken.子午仪是建立在不是首级控制或者图根控制点，高程和坐标是已知的。测站点到仪器水平轴的仪器高是通过卷尺或者钢尺量的。竖直度盘的检验是通过竖盘指标差完成，子午仪检验导线已知方位角在水平方向沿顺时针是否闭合。竖直未制动时，测量时被采用的视线是不合格的。The notekeeper records all stadia intervals, vertical or zenith angles, and azimuths, and describes all points by remarks or sketches so that the draftsman can interpret the data correctly and draw all features properly on the map. 记录人员记录所有的平距，竖直角或者天顶角和方位角，记录备注所有的测站点或者描绘草图，以便于绘图员准确的解释数据，在地图上精确地描绘地物地形特点。 In measuring vertical angles it is customary, when practical, to sight at a rod reading equal to the height of instrument above the station over which the transit is set. In this way, the difference in elevation between the center of instrument and the h.i. on the rod is the same as the difference in elevation between the station over which the transit is set and the point on which the rod is held. 测量竖直角是十分普遍的工作，实际测量中标尺读数等于子午仪在测站点到仪器中心的距离。用这种方法，测得仪器中心到标尺中丝的高程差就等于架设仪器的测站点到立尺点的高程差。Where measurements are made solely for plotting a map, usually horizontal angles or directions are estimated to 05without reading the vernier. Vertical angles are usually measured to minutes, and differences in elevation are computed to tenths of feet or to centimeters. Where elevations to the nearest foot or nearest 3 dm are sufficiently precise, the vertical angles (except for long shots) may be read by estimation without use of the vernier. 当进行单独的测图工作时，通常水平角或定向读标尺时估算到05而不读位数。竖直角读数时通常估读到分，高程差计算单位到英尺或者厘米。高程计算精确到英尺或者接近三分米是十分精确的，竖直角（除了长远的路程）或许需要通过估读来读数而不使用位数。The usual procedure of observing is to sight on the rod, the lower stadia hair being set on an even foot or decimeter mark such that the horizontal cross hair falls somewhere near the h.i. and to read the stadia interval. The horizontal cross hair is then set on the h.i. , the horizontal angle is read and the vertical angle is observed. 通常的观测工作是观测标尺，视距仪下丝设定在英尺或者分米当水平十字丝接近仪器高并且读出测站间距离。水平十字丝在仪器高，水平角和竖直角被观测到。When numerous observations are to be taken from a single station, sights to some object the azimuth of which is known are taken at intervals in order to make sure that there is no undetected movement of the lower motion of the transit.许多观测是在单一工作站上，观测一些均匀分布目标的方位角来确保经纬仪下盘转动时没有发生未监测到的运动。The rodmen choose ground points along valley and ridge lines and at summits, depressions, important changes in slope, and definite details