外文翻譯---gps全球衛(wèi)星定位系統(tǒng)

1、<p><b>　　英文文獻</b></p><p>　　The Global Positioning System</p><p>　　The global Positioning System (GPS) is revolutionizing surveying technology, Like its predecessor , the TEANSIT

2、 Doppler system, GPS shifts the scene of surveying operations from ground-to-ground measurements to ground-to-sky , with obvious implications : intervisibility of marks is no longer a criteion for their location ; operat

3、ions are possible in nearly all kinds of weather and be performed during day or night ; and the skills required to utilise the technology are different both in field ope</p><p>　　GPS was designed primarily a

4、s a navigation system, to satisfy both military and civilian needs for real-time positioning. This positioning is accomplished through the use of coded information, essentially clever timing signals, transmitted by the s

5、atellites. Each GPS satellite transmits a unique signal on two L-band frequencies: A at 1575.42 MHz and B at 1227.60 MHz(equivalent to wavelengths of approximately 19 and 24 cm, respectively).The satellite signals consis

6、t of the L-band carrier waves mo</p><p>　　There are currently eight usable satellites in orbit. These are the experimental, ”Block 1” satellites, which will be progressively replaced as the “block 2”, operat

7、ional satellites are placed into orbit beginning in 1986.By 1989 the system should be complete, with 18 satellites in six orbital planes----at about 20200 km altitude, allowing for simultaneous visibility of at least fou

8、r satellites at any time of day almost anywhere in the world. The present constellation of satellites is configured</p><p>　　As it happens, the observation geometry is equally favorable in Australia, and it

9、is possible now to obtain surveying accuracies equal to those obtainable when the system is fully configured, but only for about six hours per day, At the time of writing (November 1985),the period of maximum mutual visi

10、bility of the satellites in eastern Australia is between 6 pm and mid-night local time The period regresses by 4minutes per day (or 2 hours per month), returning to the same times a year from now. T</p><p>　

11、　As with TRANSIT , much higher accuracies are obtained in relative positioning from observations made simultaneously at two observing stations. Consequently , unless otherwise indicated , all discussion concerning data a

12、cquisition and processing will assume a two----receiver configuration. This is often referred to as the differential mode. The position differences so determined constitute the baseline vector or simply the baseline betw

13、een the points occupied by two receivers .</p><p>　　All satellite positioning systems provide ground coordinates of a receiver (or the baseline vector between a pair of receivers) in an earth—centered coordi

14、nate system, The orientation of the system is determined by the tabulated coordinates or ephemeredes of the GPS satellites. In order to relate coordinates determined by GPS surveying to the local geodetic datum a transfo

15、rmation relationship needs to be established.</p><p>　　The following factors influence the final positioning accuracy obtainable with GPS:</p><p>　　The precision of the measurement and the recei

16、ver---satellite geometry.</p><p>　　The measurement processing technique adopted.</p><p>　　The accuracy with which atmospheric and ionospheric effects can be modeled.</p><p>　　The ac

17、curacy of the satellites ephemeredes.</p><p>　　Each of these factor is discussed briefly in the next three sections.</p><p>　　GPS Measurement Types. GPS measurement can be made using either the

18、 carrier signal or the codes. Code measurements are called pseudo-ranges and can be based on either the P code or the S code. Knowledge of the properties of each of these types of measurements is necessary for understand

19、ing and evaluating GPS instruments. </p><p>　　Pseudo-ranges are the simplest to visualize geometrically , as they are essentially a measurement of distance contaminated by clock errors. Throughout this monog

20、raph, we use the terms clock , frequency standard and oscillator to denote the same thing , namely , a device for precisely measuring a time interval. When four satellites are observed simultaneously , it is possible to

21、determine the three-dimensional position of the ground receiver, and the receiver clock offset, at a single epoch . Thi</p><p>　　Carrier phase can be determined from the code-modulated signal either by using

22、 the code or other techniques . The L1 signal , which has both P code and S code modulation , can thus be tracked with S or P code receivers or with codeless receivers . The L2 signal , useful for removing ionospheric ef

23、fects for very precise applications (< 2 ppm for relative positioning ) , has no S code modulation , so that receivers for these applications must either have P code capability or operate without code .</p><

24、;p>　　It is also possible to track the phase of the 10.23 MHz P code transition signal or P code sub-carrier without knowledge of the codes . The long wavelength ( approximately 30 meter ) of this signal compared with

25、the L-band carrier allows relatively easy resolution of the integer-cycle ambiguity , producing in effect a pseudo-range measurement . However , the long wavelength makes the measurements more susceptible to multipath ef

26、fects , roughly to the same degree as pseudo-range measurements . </p><p><b>　　中文文獻</b></p><p>　　GPS全球衛(wèi)星定位系統(tǒng)</p><p>　　全球性定位系統(tǒng)(GPS) 是一種革命化勘測技術, 像它的前輩, TRANSIT 子午儀多普勒系統(tǒng)（

27、TRANSIT）, GPS 轉(zhuǎn)移勘測的操作場面從地地測量到地面對天空測量, 以明顯的涵義: 幾乎所有是操作都可以在各種天氣和晝夜完成；在野外觀測和數(shù)據(jù)處理中所需要的技能和技術是不同的。 但GPS 不僅僅是替換子午儀多普勒系統(tǒng)（TRANSIT）。 在觀測衛(wèi)星是能同時看到多顆衛(wèi)星，使得各種主要誤差得到了有效消除，因而在一公里到數(shù)千公里的距離上，GPS的相對定位精度可能達到1ppm或者更好。 這意味著, GPS地面技術能應用在短距離上，而且在

28、長距離GPS獲得高精度結(jié)果的時間比子午儀多普勒系統(tǒng)（TRANSIT）要短。</p><p>　　GPS 被設計了主要作為導航系統(tǒng), 滿足兩個對實時安置的軍事和平民需要。 這安置是完成通過對被編碼的信息的用途, 根本上聰明定時信號, 由衛(wèi)星傳輸。 各枚GPS衛(wèi)星傳輸一個獨特的信號在二個L 波段頻率: L1 是1575.42 兆赫和L2是1227.60 MHz（各自大約19 和24 cm 波長）, 衛(wèi)星信號包括L 波

29、段載體波浪調(diào)整以"標準" 或S 代碼(以前稱C/代碼),導航電文信息包含在P碼中，衛(wèi)星的坐標作為時間，也就是 "廣播星歷表" 。 S碼中的信息主要是為民用服務，產(chǎn)生范圍測量精確度大約10 米, 航海也由這個代碼提供標準定位服務, P代碼主要是為軍事和被選擇的某些民用方面服務，產(chǎn)生范圍測量精度大約1米，航海由這個代碼提供精確定位服務 雖然兩個代碼都能用來測量，但有一種更加準確的方法是測量載體信號,

30、因此, 我們不會談論詳細代碼的特征在這篇專題論文里。 </p><p>　　目前有八枚能用的衛(wèi)星在軌道運行。從1986年開始，“Block 1”試驗衛(wèi)星將被“Block 2”工作衛(wèi)星取代。到1989年，該系統(tǒng)就應該建立完成了，將有18顆衛(wèi)星在距離地球20200公里高度的六個軌道運行，如果這樣的話，在世界的任何一個地方任何時間都至少能接收到4顆以上的衛(wèi)星。在當?shù)貢r間下午6點和午夜之間，衛(wèi)星的最大相互可見性出現(xiàn)在東

31、澳大利亞。這個時間每天退后4分鐘（也就是一個月退后2小時），從現(xiàn)在返回到次年。當從1985年晚些時候衛(wèi)星再被發(fā)射后， 這個有用的可見性的期間將增加。</p><p>　　正如子午儀多普勒系統(tǒng)，GPS在兩個測站上可以同時獲得更高精度的相對定位結(jié)果。如果這樣，所有的關于數(shù)據(jù)采集和處理的任務將由一臺雙頻接收機承擔，這就是常說的差分定位。 由這樣確定的定位誤差構(gòu)成了基礎線傳染媒介或簡單地基礎線，即由兩臺接收機所確定的。&

32、lt;/p><p>　　在地心坐標系中，所有衛(wèi)星定位系統(tǒng)提供接收機的地面坐標(或基礎線傳染媒介在一對接收器之間)，系統(tǒng)的取向是堅定的，由GPS 衛(wèi)星制成表的坐標或星歷。為了和被確定的坐標系有聯(lián)系，本機關系坐標的確定由GPS 勘測變革關系需要被建立的測地學基準。以下因素將影響GPS獲得最后精確定位的準確性：</p><p>　　(1) 儀器的精度和被接收到的衛(wèi)星的幾何位置。 (2) 所采取的測

33、量處理技術。</p><p>　　(3) 大氣層和電離層的影響。 (4) 衛(wèi)星星歷的準確性。</p><p>　　以上這些因素將簡要地被談論在下三個部分。</p><p>　　GPS 測量類型。GPS 測量可以使用載體信號或代碼。代碼測量叫作偽距測量，并且也能根據(jù)或P 代碼或S 代碼。掌握每種測量類型對你了解和評估GPS儀器是非常必

34、要的。 </p><p>　　偽距觀測在幾何形象上是最簡單的，如同它們在距離測量時被時鐘誤差影響。在這篇專題論文過程中, 我們使用期限時鐘, 頻率標準和擺動器表示同樣事件, 即一個設備為精確地測量間隔時間。當四顆衛(wèi)星在空中被同時觀察到時，它可以確定地面接收機的三維位置以及接收機時鐘垂距。在測量技術中，這是簡單的距離測量，由衛(wèi)星作為控制站。在這種技術中，它的精度由空中的4顆衛(wèi)星和接收機所組成的幾何圖形來確定。 最佳

35、的幾何位置將是何時衛(wèi)星是在每個四個象限和海拔角度在40度到70度。 但是, 偽距觀測的精度沒有載波相位測量的精度高。為了達到10 米位置準確性從P編碼測量或100 米從S 代碼測量(滿足航海要求),它所設計的代碼結(jié)構(gòu)必須要達到米級定位精度。盡管如此，1989 年當系統(tǒng)變得完全可使用時 ，更加精確的P代碼可能將被編成密碼, 并且可以因此不能作為非軍事用途。另外一個影響偽距觀測精度的是出現(xiàn)多路徑效應，那是衛(wèi)星的某一分數(shù)傾向發(fā)信號到達接收器天

36、線通過反射地面或其它表面。多路徑效應的作用大小和署名依靠天線，天線的設計和高度在地面之上，但大概不能被減少在幾個公寸之下以實用配置。 </p><p>　　載波測量階段可能是堅定的從代碼被調(diào)整的信號或者由使用代碼或其它技術。L1 信號被P 代碼和S 代碼模塊化, 因而被跟蹤以S 或P 代碼接收器或與codeless 接收器。 L2 信號用來去除電離層作用，非常精確應用(< 2 ppm 為相對安置), 沒有S