【導讀】何與物理信息的攝影測量學的分支學科。在航空攝影測量學方面,地形圖的成圖方法已從。模擬攝影測量、解析攝影測量發(fā)展到目前的數(shù)字攝影測量。本次設(shè)計的主要內(nèi)容是：首。量采用四等水準測量方法。其次、通過飛機用航攝儀對測區(qū)進行航空攝影,獲得該地區(qū)的。航空攝影像片，然后通過全數(shù)字攝影測量系統(tǒng)和加密軟件在室內(nèi)進行像片控制點的加密，范》的規(guī)定對采集的矢量數(shù)據(jù)進行編輯成正式地形圖成果。最后上交整個過程中每一步。的原始資料和成果資料。

　　

【正文】 當我們用α和 S分別表示垂直角和水平距離時， A 點和 B點之間的高差為： hAB=S179。 tanα +i – v i 是 A 點上儀器中心的高度， v 是 B 點上目標中心的垂直高度，垂直角為仰角時為正，俯角時為負天頂距總是正的，但是自然的當超過了 90176。時，它們將產(chǎn)生一個相反的結(jié)果。普通精度要求下，三角高程 測量方法測高差水平距離不能超過 300m，如果要求高的精度，則要相應縮短距離。因為超過 300m 時，地球曲率和折光影響必需考慮為了消除地球曲率和折光改正的不確定因素，垂直角觀測時應采用在觀測方向兩端盡量同時相向觀測的方法。這種觀測稱為垂直角對向觀測。線兩端正確的高程之差是計算得到的兩高程值的平均值，不管計算有無考慮球氣差 .這里需要注意的是，測量者在水準測量工作中使用的是參考地球“平均”表面的 正高 ，這個平均表面描述為 MSL。然而， GPS 方法給出的是地安徽建筑工業(yè)學院 本科畢業(yè)論文 30 球橢球面到地面站的大地高。 安徽建筑工業(yè)學院 本科畢業(yè)論文 31 Methods of Elevation Determination An elevation is a vertical distance above or below a reference vertical distance can be referenced to any datum, in surveying, the reference datum that is universally employed is that of mean sea level (MSL). MSL is assigned a vertical value (elevation) of ft or m. All other points on the earth can be described by the elevations above or below zero. Permanent points whose elevations have been precisely determined (benchmarks) are available in most areas for survey use. 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. 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. 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 is assigned a vertical value (elevation) of ft or in elevation may be measured by the following methods: 1. Direct or spirit leveling, by measuring vertical distances directly. Direct leveling is most precise method of determining elevations and the one monly used. 2. Indirect or trigonometric leveling, by measuring vertical angles and horizontal or slope distances. 3. Stadia leveling, in which vertical distances are determined by tacheometry using engineer’s transit and level rod。 planetable and alidade and level rod。 or selfreducing tacheometer and level rod. 4. Barometric leveling, by measuring the differences in atmospheric pressure at various stations by means of a barometer. 5. Gravimetric leveling, by measuring the differences in gravity at various stations by means of a gravimeter for geodetic purposes. 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 安徽建筑工業(yè)學院 本科畢業(yè)論文 32 accuracies from 15 to 50 cm in distances of 60 and 100 km, respectively, have been 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. 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. Standard deviations in elevation differences of to m are possible under these conditions. Spirit leveling The most precise method of determining elevations and most monly use method is direct leveling or spirit leveling which means measuring the vertical distance directly. 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. 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. 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. The elevation of point B can be determined by equation 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. But some terms should be mentioned from above. 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. 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. HA + a refers to the Height of Instrument (HI) which is the elevation of the line of sight through the level. 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 安徽建筑工業(yè)學院 本科畢業(yè)論文 33 practical operation. Trigonometric Leveling Trigonometric leveling is used where difficult terrain, such as mountainous areas, precludes the use of conventional differential leveling. The modern approach is to measure the slope distance and vertical angle to the point in question. Slope distance is measured using electromagic distance measurers and the vertical (or zenith) angle using a theodolite, or the total station that integrate these two instruments into a single instrument. Total stations contain builtin 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. The basic concept