外文翻譯---高程測量方法

1、<p><b>　　附錄：</b></p><p><b>　　高程測量方法</b></p><p>　　高程是高于或低于一個參考基準(zhǔn)的一個垂直距離。雖然垂直距離可以參考任何一個基準(zhǔn)，但是在測量上，這個參考基準(zhǔn)一般使用的是平均海平面（MSL）。MSL被賦予一個0.000英尺或0.000米的高程，地球上所有其它點可以用高于或低于0的高程來

2、描述。高程精確測出的永久點（水準(zhǔn)點）被用于大多數(shù)區(qū)域的測量工作.在中國，利用青島驗潮站從1950年到1956年7年的觀測數(shù)據(jù)處理】和平差，建立了56黃海高程系統(tǒng)。1987年，在依照了驗潮站1952到1979年的觀測資料后，這個基準(zhǔn)被進(jìn)一步精確——反映長時期海潮變化的85國家高程基準(zhǔn)建立起來。雖然，嚴(yán)格說來，國家高程基準(zhǔn)在特殊的點上與MSL并不恰好吻合，術(shù)語MSL一般還是用來描述它。MSL高程的賦值為0.000英尺或米，高程的差異【高差】

3、可以由下列方法測得：</p><p>　　1.水準(zhǔn)測量，直接測得垂直距離，水準(zhǔn)測量是高程測量方法中精度最高、使用最普遍的方法</p><p>　　2.三角高程測量，利用測量豎直角和水平或斜距來測高程</p><p>　　3.視距高程測量，利用視距測量，使用工程經(jīng)緯儀和水準(zhǔn)尺；平板儀和照準(zhǔn)儀和水準(zhǔn)尺；或者自處理視距儀和水準(zhǔn)尺測得垂直距離</p><

4、p>　　4.氣壓水準(zhǔn)測量，通過使用氣壓計測量不同站點大氣壓力的差值來測高程</p><p>　　5.重力水準(zhǔn)測量，通過使用重力計測量不同站點的重力值差值來測高程，用于大地測量學(xué)的目的</p><p>　　6.慣性定位系統(tǒng)，含有一個慣性平臺，具有三個互相垂直軸，其中一個是“向上”的，所以這個系統(tǒng)產(chǎn)生的輸出其中一個就是高程。各自地，據(jù)相關(guān)報告，在60和100km的距離上，其精度能達(dá)到15

5、到50cm，這種裝置成本極高，只限于非常大的項目，這些項目地質(zhì)、氣象、授時、以及施特殊限制在傳統(tǒng)方法上</p><p>　　7. GPS高程測量，它的參考面是地球橢球面，但是如果在測區(qū)有充分的高程點，可以修正至高程基準(zhǔn)上來，在這種情況下，其高差的標(biāo)準(zhǔn)差能夠達(dá)到0.053到0.094米。</p><p><b>　　水準(zhǔn)測量</b></p><p&g

6、t;　　精度最高、使用最普遍的高程測量方法就是直接測垂直距離的水準(zhǔn)測量方法。微差水準(zhǔn)測量是利用測量者的水準(zhǔn)儀和有刻度的尺來測定遠(yuǎn)距離的相隔點的高差。</p><p>　　例如，確定欲測關(guān)于點A的點B的高程，（如圖1），A點的高程已知（BM點），在A和B點之間的中點處安置水準(zhǔn)尺，分別以a和b代表在這兩處水準(zhǔn)尺上的讀數(shù)。那么，儀器整平后的視線高程就是：HA + a。B點的高程可以由方程來確定</p>&

7、lt;p>　　HB=HA + a － b</p><p>　　除確定B點的高程之外，其它點的高程，低于視線的和水準(zhǔn)儀可以看見的點，都可以以相似的方法得到。但是上面的一些術(shù)語需要提一下，a 被稱為后尺讀數(shù)，是一個放在已知高程點上的尺的讀數(shù)，用來求得儀器視線的高程。b 被稱為前尺讀數(shù)，是一個放在轉(zhuǎn)點、水準(zhǔn)點、或者是臨時水準(zhǔn)點之上的尺的讀數(shù)，用來確定該點的高程。HA + a 指的是儀器高度（HI），是過水準(zhǔn)儀的視

8、線的高程。由于大氣折光的緣故，實際上視線是有些彎曲的，曲率和折光的影響可以被當(dāng)作可忽略的值，不必加入球氣改正，如果在實際工作中后視距和前視距是相等的。</p><p><b>　　三角高程測量</b></p><p>　　三角高程測量適用于困難地形，例如在山區(qū)，不能使用常規(guī)的微差水準(zhǔn)測量?，F(xiàn)代的三角高程測量方法是測量到未知點的斜距和垂直角，斜距由電磁波測距儀測得，垂直

9、角（或天頂距）由經(jīng)緯儀測得，或者利用整合了這兩種儀器為一體的全站儀來測。全站儀包含了內(nèi)置的微處理器，用來根據(jù)測得的斜距和垂直角計算和顯示水平距離，這種后來的設(shè)備導(dǎo)致了三角高程測量被廣泛用于多種高度測量工作，包括測繪等高線，三角高程測量的基本原理可以看圖2。</p><p>　　當(dāng)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：</p><p>　　hAB=S×ta

10、nα+i – v</p><p>　　i 是A點上儀器中心的高度，v是B點上目標(biāo)中心的垂直高度，垂直角為仰角時為正，俯角時為負(fù)天頂距總是正的，但是自然的當(dāng)超過了90°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(yīng)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(yīng)采用在觀測

11、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(zhǔn)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方法給出的是地球橢球面到地面站的大地高。 </p><p>　　Methods of Elevation Determ

12、ination</p><p>　　An elevation is a vertical distance above or below a reference datum.Although vertical distance can be referenced to any datum, in surveying, the reference datum that is universally employed

13、 is that of mean sea level (MSL). MSL is assigned a vertical value (elevation) of 0.000 ft or 0.000 m. All other points on the earth can be described by the elevations above or below zero. </p><p>　　Permanen

14、t 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

15、 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

16、 tidal stations from 1952 to 1979. Although, strictl</p><p>　　1. Direct or spirit leveling, by measuring vertical distances directly. Direct leveling is most precise method of determining elevations and the

17、one commonly used. </p><p>　　2. Indirect or trigonometric leveling, by measuring vertical angles and horizontal or slope distances.</p><p>　　3. Stadia leveling, in which vertical distances are d

18、etermined by tacheometry using engineer’s transit and level rod; plane-table and alidade and level rod; or self-reducing tacheometer and level rod.</p><p>　　4. Barometric leveling, by measuring the differenc

19、es in atmospheric pressure at various stations by means of a barometer. </p><p>　　5. Gravimetric leveling, by measuring the differences in gravity at various stations by means of a gravimeter for geodetic pu

20、rposes. </p><p>　　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.Vertical

21、accuracies from 15 to 50 cm in distances of 60 and 100 km, respectively, have been reported.The equipment cost is extremely high and applications are restricted to very large projects where terrain, weather, time, and ac

22、cess impose special constraints on traditional methods.</p><p>　　7. GPS survey elevations are referenced to the ellipsoid but can be corrected to the datum if a sufficient number of points with datum elevati

23、ons are located in the region surveyed. Standard deviations in elevation differences of 0.053 to 0.094 m are possible under these conditions.</p><p>　　Spirit leveling </p><p>　　The most precise

24、method of determining elevations and most commonly use method is direct leveling or spirit leveling which means measuring the vertical distance directly. Differential leveling is used to determine differences in elevatio

25、n 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

26、 A (see Figure 1), the elevation of which (</p><p>　　HB=HA + a － b</p><p>　　In addition to determining the elevation of point B, the elevations of any other points, lower than the line of sight

27、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 establis

28、h 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 </p><p>　　Trigonometric Leveling</p>&

29、lt;p>　　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 angl

30、e to the point in question. Slope distance is measured using electromagnetic distance measurers and the vertical (or zenith) angle using a theodolite, or the total station that integrate these two instruments into a sing

31、le instrument. Total stations contain built-in microprocessors that ca</p><p>　　hAB=S×tanα+i – v</p><p>　　where i is the vertical height of the measuring center of the instrument above A an

32、d 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 gr