出其中一个就是高程。）
Vertical accuracies from 15 to 50 cm in distances of 60 and 100 km, respectively, have been reported.（各自地，据相关报告，在60和100km的距离上，其精度能达到15到50cm）
The equipment cost is extremely high and applications are restricted to very large projects where terrain, weather, time, and access impose special constraints on traditional methods.（这种装置成本极高，只限于非常大的项目，这些项目地质、气象、授时、以及？？施加特殊限制传统方法上） 7. GPS survey elevations are referenced to the ellipsoid but can be corrected to the datum if a sufficient number of points with datum elevations are located in the region surveyed.（GPS高程测量，它的参考面是地球椭球面，但是如果在测区有充分的高程点，可以修正至高程基准上来） Standard deviations in elevation differences of 0.053 to 0.094 m are possible under these conditions.（在这种情况下，其高差的标准差能够达到0.053到0.094米。） Spirit leveling （水准测量）
The most precise method of determining elevations and most commonly use method is direct leveling or spirit leveling which means measuring the vertical distance directly.（精度最高、使用最普遍的高程测量方法就是直接测垂直距离的水准测量方法）
Differential leveling is used to determine differences in elevation between points that are remote from each other by using a surveyor’s level together with a graduated measuring rod.（微差水准测量是利用测量者的水准仪和有刻度的尺来测定远距离的相隔点的高差）
For example, to determine the elevations of desired point B with respect to a point of known elevation A (see Figure 1), the elevation of which (BM) is known to be above sea level, the level is set up at intermediate point between A and B, and rod readings are taken at both locations as a and b respectively.（例如，确定欲测关于点A的点B的高程，（如图1），A点的高程已知（BM点），在A和B点之间的中点处安置水准尺，分别以a和b代表在这两处水准尺上的读数）
Then the elevation of the line of sight of the instrument (being horizontal) is known to be the line of sight of the instrument HA + a.（那么，仪器（整平后）的视线高程就是：HA + a） The elevation of point B can be determined by equation（B点的高程可以由方程来确定）
HB=HA + a － b
In addition to determining the elevation of point B, the elevations of any other points, lower than the line of sight and visible from the level, can be determined in a similar manner.（除确定B点的高程之外，其它点的高程，低于视线的和水准仪可以看见的点，都可以以相似的方法得到。） But some terms should be mentioned from above.（但是上面的一些术语需要提一下）
a is called Backsight (BS) which is a rod reading taken on a point of known elevation in order to establish the elevation of the instrument line of sight.（a 被称为Backsight，是一个放在已知高程点上的尺的读数，用来求得仪器视线的高程。）
b is called Foresight (FS) which is a rod reading taken on a turning point, benchmark, or temporary benchmark in order to determine its elevation.（b 被称为Foresight，是一个放在转点、水准点、或者是临时水准点之上的尺的读数，用来确定该点的高程）
HA + a refers to the Height of Instrument (HI) which is the elevation of the line of sight through the level.（HA + a 指的是仪器高度（HI），是过水准仪的视线的高程）
Owing to refraction, actually the line of sight is slightly curved, the effects of curvature and refraction for the horizontal distance can be reduced to a negligible amount and no correction for curvature and refraction is necessary if backsight and foresight distances are balanced in practical operation.（由于大气折光的缘故，实际上视线是有些弯曲的，曲率和折光的影响可以被当作
可忽略的值，不必加入球气改正，如果在实际工作中后视距和前视距是相等的。） Trigonometric Leveling三角高程测量
Trigonometric Leveling is used where difficult terrain, such as mountainous areas, precludes the use of conventional differential leveling.
三角高程测量被用于复杂的地形，如山区，排除了传统的微差水准测量
The modern approach is to measure the slope distance and vertical angle to the point in question. Slope distance is measured using electromagnetic distance measures and the vertical (or zenith) angle using a theodolite, or the total station that integrate these two instrument into a single instrument.
这个现代手段是测量测站距离未知点的斜距和垂直角。斜距是通过电子测距仪测量的，垂直角（或天顶距）是通过经纬仪测量的，或者使用全站仪测量，全站仪集测距、测角功能于一身。
Total stations contain built-in microprocessors that calculate and display the horizontal distance from the measured slope distance and vertical height. This latter facility has resulted in trigonometrical leveling being used for a wide variety of heighting procedures, including contouring.
全站仪包含了内置的微处理器，它通过测量所得的斜距和垂直高度计算和呈现水平距离。这个新型的设备使得三角高程测量被广泛应用在各种各样的高程测量中，包括等高线。
The basic concept of trigonometrical leveling can be seen from Figure 2. When measuring the vertical angle α and the horizontal distance S is used, then the difference in elevation hAB between ground points A and B is therefore:
hAB = S*tan α+ i - v
三角高程测量的最基本的概念能够从图2上看出。当测量的垂直角α和水平距离S被使用，然后地面 点A和B的高差如下：
hAB = S*tan α + i - v
where i is the vertical height of the measuring center of the instrument above A and v is the vertical height of the center of the target above B. The vertical angles are positive for angles of elevation and negative for angles of depression. The zenith angles are always positive, but naturally when greater then 90 they will produce a negative result.
i是一起的测量中心距离地面点A的垂直高度，v是目标中心距离地面点B的垂直高度。垂直角的值，仰角为正，俯角为负。天顶角总是为正，但是当然当大于90度的时候也会产生一个负值。
Trigonometrical leveling method of determining difference in elevation is limited to horizontal distance less than 300 m when moderate precision is sufficient, and to proportionately shorter distance as high precision is desired. For the distance beyond 300 m the effects of curvature and refraction correction must be considered and applied.
三角高程测量方法仅限于水平距离低于300米内的高差测量，当中等精度是足够的，和依比例的、所要求更高精度范围内的更短距离的测量。对于那些距离超过300米的，地球曲率和大气折光的影响必须得考虑和应用。
To eliminate the uncertainty in the curvature and refraction correction, vertical-angle observations are made at both ends of the line as close in point of time as possible. 为了消除地球曲率和大气折光中不确定因素的影响，垂直角观测应该在测站的两端分别观测，越靠近同一时间点越可能。
This pair of observation is termed reciprocal vertical-angle observation. The correct difference in elevation between the two ends of the line is the mean of the two values computed both ways either with or without taking into account curvature and refraction.
这一对观测叫做相反的垂直角观测。测距两端点间的高差改正是两个测量值的平均值，测量值可以考虑或不考虑地球曲率和大气折光。
The important notes should be mentioned here is that surveyors used to working with spirit levels have referenced orthometric heights (H) to the “average” surface of the earth, as depicted by MSL. However, the elevation coordinate (h) given by GPS solutions refers to the height from the surface of the ellipsoid to the ground station.
这个重要的说明应该在这里被提到，测量员进行水准测量时过去常常参考距离平均地球表面的正高（H），这个平均地球表面被描述为大地水准面。然而，GPS提供的高程坐标系引用的是参考椭球距离地面基站的高度。
Topographic Surveying 地形测量
Introduction 序言
Topographic surveys are made to determine configuration (relief) of the earth's surface and to locate nature and cultural features on it .By means of various lines and conventional symbols,topographic maps are produced from survey data. A topographic map is a large-scale representation of a portion of the earth's surface showing culture,relief,hydrography,and perhaps vegetation.Cultural（artificial）features are the products of people,such as roads,trails,buildings,bridges,canals,and boundary lines.Names and legends on maps identify the features.
地形图地形测量用来确定地球表面的形状，定位自然和人文地物。通过各种线条和规定的符号，就可以根据测量数据绘制地形图。地形图是大比例表示部分地球表面的人工建筑，救灾，水文，也许植被。人文建筑是人类的产物，例如道路，小径，建筑，桥梁，运河和边界线。地图上的名称和图例是识别的特征。 Topographic maps are made and used by engineers to determine the most desirable and economical locations of
highways,railroads,canals,pipelines,transmission lines,reservoirs,and other facilities；by geologists to investigate mineral,oil,water,and other resources；by foresters to locate fire-control roads and towers；by architects in housing and landscape design；by agriculturists in soil conservation work；and by archeologists,geographers,and scientists in numerous fields. 地形图是工程技术人员用来确定公路，铁路，管，管道，线路，水库，和其他设施最可取的和经济的位置；地质学家用来研究矿物，油，水，和其他资源；林务员用来定位消防道路和塔；建筑师用来设计住房和景观；农学家用来水土保持工作；考古学家，地理学家，许多领域的科学家也都有运用。
A planimetric map depicts natural and natural features in plan only.A hypsometric map shows relief by conventions such as contours,hachures,shading,and tinting.
一幅平面图仅仅在平面中描绘了人文建筑及其特征。一幅地形图则显示了地形，例如等高线、晕线、阴影和着色。
Methods for Topographic Surveying地形测量方法
Topographic surveys are conducted by either aerial（photogrammetric）or ground （field）methods,and often a combination of both.Refined equipment and procedures available today have made photogrammetry accurate and economical；hence,almost all topographic mapping projects covering large areas now employ this method.
地形测绘是由空中（摄影测量)或地面方法完成的，而且经常是两者的结合。现今精良的设备和程序使得摄影测量很精确、经济，因此，现在几乎所有覆盖大面积地区的地形测图工程都使用这种方法。
Ground surveys are still frequently used,however,especially for preparing large-scale maps of
small areas. Even when photogrammetry is utilized,ground surveys are necessary to establish control and to field-check mapped features for accuracy.This chapter concentrates on ground methods.Several feild procedures for locating topographic features,both horizontally and vertically,will be described.
地面测量仍是经常使用的,然而,尤其是准备对大比例尺地图的小区域测图。即使使用摄影测量,地面测量为测量建立控制和现场检查仍然是必要的,。本章集中于地面的方法。一些行业程序定位地形特征,在水平方向和垂直方向,将被描述。
Control for Topographic Surveys
The first requirement of any topographic survey is good control,whether the survey is done by ground or aerial methods.Control is classified as either horizontal or vertical.
地形测量无论调查是用地面还是空中的方法，第一个要求都是良好的控制,。控制是分为水平或垂直控制。 Horizontal control is provided by two or more points on the ground,precisely fixed in position horizontally by distance and direction.It is the basis for map scale and locating topographic features.Horizontal control is usually established by traversing,triangulation,trilateration,or inertial and satellite methods,and can be filled in photogrammetrically for large areas. 平面控制由地面上的两个或多个点来确定，精度由平面坐标位置的距离和方向来固定。地图比例尺和地形特征是基本的要素。平面控制通常由导线测量，三角测量，三边测量，重力和卫星的方法和大区域的摄影测量来确定。
For small areas, horizontal control for topographic work is generally established by a traverse, although a single line may suffice in some cases. Triangulation and trilateration furnish themost economical basic control for surveys extending over a state or the entire United States. These techniques may, however, give way in the future to inertial systems and Satellite Doppler receivers. Monuments of the state plane coordinate systems are excellent for all types of work ,but unfortunately more are needed in most areas
地形测量中，对于一些小面积的水平控制测量工作，尽管在某些情况下单导线就可以满足精度要求，但是通常还是用导线测量。在一个州甚至整个美国，三角测量和三边测量是最经济的基础控制测量方式。无论怎样，这些方技术给未来重力系统和卫星多普勒接收器提供了方法。州的平面坐标系统的埋石对测量的各种类型是有必要的，但是不幸的是大多数区域的埋石太少。
Specified maximum allowable closure errors for both horizontal and vertical control should be established in advance of field work
在外业之前，为了平面和高程控制的建立要指定最大的允许限差。
Vertical control is provided by bench marks in or near the tract to be surveyed. .It becomes the foundation for correctly portraying relief on a map A vertical control net is established by lines of levels starting form and closing on bench marks. Elevations are ascertained for all traverse hubs, with provision in some cases for marks set nearby and out of the way of construction. A lake surface is a continuous turning point or bench mark and may sometimes be used .Even a gently flowing stream may serve as supplementary control. Trigonometric and barometric leveling can be employed to extend vertical control in rugged terrain, but the latter is less accurate. 高程控制由测区的水准基点提供。在地形图上它成了正确描绘地形的基础。一个高程控制网由起止于水准基点的水准路线构成。导线中心确定了高程，在一些情况下，规定要在建筑物附近或外面做标记。湖的表面是一个连续的转折点或标记，有时会使用。即使轻轻流淌的河水可作为辅助控制。在崎岖的地形三角高程和气压水准可以用来延长高程控制，但后者是不准确的。
Topographic details are usually built upon a framework of traverse hubs whose positions and elevations have been established. Any errors in the hub positions or their elevations are reflected
in the location of topography. It is advisable, therefore, to run, check, and adjust the traverse and level circuits before a topographic detail survey is begun ,rather than carry on both processes simultaneously. This is particularly true in plane table work, where an error in elevation or position of an occupied station will displace the plotted locations of all cultural features and contours
地形碎步测量经常建立在导线节点网上，且这些节点的平面坐标和高程已确定。节点的水平和高程误差都反映在地形位置上。因此，在地形碎步测量开始之前对导线环和水准环实施检核和平差是适当的，而不是同时实施这两个工作。这在平面室内工作中也是绝对正确的，在这里实测站的高程和坐标误差会显示在标绘的地物的位置和等高线上。
Field measurement errors are more difficult to eliminate than those in mapping procedures .Even though plotting measurements that have been made to the nearest 0.01ft and 1 sec is not possible ,the data may be used for other purposes .Thus special care is required in taking and recording field date
野外测量误差比绘图过程中的误差更难消除。即使把已测得的数据展绘到0.01英尺和1秒是不可能的，但这些数据还可以用在其他方面。因此获取和记录野外数据时要特别小心。
The kind of control (traverse, triangulation, or trilateration)and method selected to get topographic details govern the speed, cost, and efficiency of a topographic survey. A theodolite-EDMI combination total station instrument with tracking system, data storage accessory, and voice recorder plus a communication system for descriptions simplify the note keepers job and reduce field errors. Sketches still must be made in field books, however. Various equipment combinations can be selected for the location methods discussed in succeeding sections 地形碎步控制测量（导线测量，三角测量，三边测量）的方法的选择决定了测量的进度，花费，和地形测量的效率。经纬仪和电子测距仪的结合，具有跟踪系统，数据存储设备，声音记录器，加上通讯系统的全站仪简化了记录员的工作，减少了野外测量误差，但是仍需要在野外测量簿上画出草图。不同仪器配合使用进行位置测定的方法将在接下来进行讨论。
Methods of locating Topographic Details in the Field 野外地形碎步测定的方法
Objects to be located in a survey can range from single points to meandering streams and complicated geological formations. The process of tying topographic details to the control net is called detailing.
要定位的目标可以从单个点到曲折的小溪和复杂的地形结构。联系碎步测量到控制网的过程称为碎步测量。
Seven methods used to locate a point P in the field are illustrated in Fig11-1. All are based on horizontal control. One line , AB, must be fixed in each of the first four methods, and its length known in methods 1, 2, and 4. Positions of three points must be known or identifiable to apply the seventh method called resection or the three-point problem. Quantities to be measured in the respective diagrams are:
在图11-1中显示了在野外确定p点位置的7中方法。所有方法都以水平控制为基础。在前四种方法中线AB必须测定，在1,2,4方法中需要知道它的长度。第七种方法叫做后方交会或三点问题，其中三个点的坐标必须知道或者可以测定。各个图需测量的数据是： (1):Two distances;两个距离 (2)Two angles两个角
(3)One angle and the adjacent distance一个角和相邻边
(4)One angle and the opposite distance(two possible points P