【正文】 地發(fā)揮GPS的定位精度，專用于這種目的的接收機被稱為大地型接收機，是接收機中性能最好的一類。在整周未知數(shù)解固定后，即可進行每個歷元的實時處理， 只要能保持四顆以上衛(wèi)星相位觀測值的跟蹤和必要的幾何圖形，則流動站可隨時給出厘米級定位結(jié)果。(1) GPS系統(tǒng)用途廣泛目前，GPS系統(tǒng)的應(yīng)用己經(jīng)十分廣泛，我們可以應(yīng)用GPS信號進行海、空和陸地的導(dǎo)航，導(dǎo)彈的制導(dǎo)，大地測量和工程測量的精密定位，時間的傳遞和速度的測量等。這一多元化的空間資源環(huán)境，促使國際民間形成了一個共同的策略，即一方面對現(xiàn)有系統(tǒng)從分利用，一方面積極籌建民間GNSS系統(tǒng)，待到2010年前后，GNSS純民間系統(tǒng)建成，全球?qū)⑿纬蒅PS/GLONASS/GNSS三足鼎立之勢，才能從根本上擺脫對單一系統(tǒng)的依賴，形成國際共有、國際共享的安全資源環(huán)境。15。國際民間的這一策略，反過來有影響和迫使美國對其GPS 使用政策做出更開放的調(diào)整。用于建立陸地海洋大地測量基準，進行高精度的海島陸地聯(lián)測以及海洋測繪。RTK 技術(shù)的應(yīng)用(1)各種控制測量傳統(tǒng)的大地測量、工程控制測量采用三角網(wǎng)、導(dǎo)線網(wǎng)來施測，不僅費工費時，要求點與點之間通視，而且精度分布不均勻，且在外業(yè)不知精度如何，采用常規(guī)的GPS靜態(tài)測量、快速靜態(tài)、偽靜態(tài)方法，在外業(yè)測設(shè)過程中，不能實時知道定位精度，如果測設(shè)完成后，回到內(nèi)業(yè)處理，發(fā)現(xiàn)精度不合要求，還必須返測，而采用RTK 來進行控制測量，能夠?qū)崟r知道定位精度，如果點位精度要求滿足了，用戶就可以停止觀測了，而且知道觀測質(zhì)量如何，這樣可以大大提高作業(yè)效率。RTK 技術(shù)常規(guī)的GPS測量方法，如靜態(tài)、快速靜態(tài)、動態(tài)測量都需要事后進行解算才能獲得厘米級的精度，而RTK 是能夠在野外實時得到厘米級定位精度的測量方法，它采用了載波相位動態(tài)實時差分(Realtime Kinematic)方法，是GPS 應(yīng)用的最大里程碑，它的出現(xiàn)為工程放樣、地形測圖，各種控制測量帶來了新曙光，極大地提高了外業(yè)作業(yè)效率。相位觀測值得精度高至毫米，但前提是解出整周模糊度，因此只有在相對定位、并有一段連續(xù)觀測值時才能使用相位觀測值，而要達到優(yōu)于米級的定位精度也只能采用相位觀測值。GPS系統(tǒng)的實時導(dǎo)航定位精度很高，美國在1992年起實行了所謂的SA政策，即降低廣播星歷中衛(wèi)星位置的精度，降低衛(wèi)星鐘改正數(shù)的精度，對衛(wèi)星基準頻率加上高頻的抖動(使偽距和相位的量測精度降低)，后又實行了AS政策，即將P碼改變?yōu)閅碼，即對精密偽距測量進一步限制，而美國軍方和特許用戶不受這些政策的影響，但美國為了獲得更大的商業(yè)利益，這些政策終將被取消。GPS系統(tǒng)的空間部分由21顆衛(wèi)星組成，均分布在 6個軌道上，地面高度為20000余公里，軌道傾角為55度，扁心率約為0，周期約為 12小時，衛(wèi)星向地面發(fā)射兩個波段的載波信號，(L1波段)(L2波段)，衛(wèi)星上安裝了精度很高的原子鐘，以確保頻率的穩(wěn)定性，在載波上調(diào)制有表示衛(wèi)星位置的廣播星歷，用于測距的C/A 碼和P碼，以及其它系統(tǒng)信息，能在全球范圍內(nèi)，向任意多用戶提供高精度的、全天候的、連續(xù)的、實時的三維測速、三維定位和授時。Used for moni toring plate motion state of the earth and the earths crust deformation。Summarizing The Global Positioning SystemAbstract: Global Positioning System is based on the background of the United States Department of is designed,invested,developed,and operated by the United States Department of Defense ,GPS is a satellitebased positioning and time transfering GPS positioning function has a wide range of applications in the modern measurement and a more modern technology is also widely used in modernization building, and now GPS has also been shown to be an important civilian munities of interest, and increasingly wide range of applicated.Keyword:GPS,Locating，RTK，Lay out，Survey1. Background The 50s, the former has not launched humanities first artificial earth satellite, the American scientists in along its track research in, had discovered the Doppler shift phenomenon, and has facilitated Doppler satellite navigation posi tioning system pleting using this principle, has obtained the enormous success in the military and the civi aspect, was in a navigation localization history leap, our country once has also introduced many Doppler receiver, applied to the island association measured, the Earth explored and so on the applied to the island association measured, the Earth explored and so on the domain. But because Doppler satellite orbit highly low, signalcarrier frequency low, the track precision enhances with difficulty, causes the pointing accuracy lowly, satisfies the geodetic survey or the project survey request, is more impossible to use in the astronomy Earth dynamics research. In order to enhance the satellite positioning the precision,US started from 1973 to prepare for construction global positioning system GPS (Global Positioning System).After has entered the plan proof, the system test stage,started in 1989 to launch the official work satellite,and pletely pleted in 1994, investment use. The GPS system spaceartially is posed by twenty one satellites, evenly distributes in six orbit, the ground level is 20,000 Kilometers, the inclination of orbit is 55, the flat heart rate approximately is 0, the week contract is 12 hours, the satellite to the earth launching two wave bands intelligence signals,the intelligence signal frequency respectively is mega cycles per second (the L2 wave band), on the satellite has installed the precision very high atomic clock, guarantees the frequency the stability, modulates in the carrier has the expression satellite position the broadcast star experience, use in the range finder C/A code and P yard, as well ad other system information, can in the global scope, to willfully multiuser provide the high accuracy, allweather, is continual, realtime three dimensional measures fast, the three dimensional localization and the time service. The GPS system control section by is located in the American foundations of the states 5 monitoring stations to be posed, these stand did not ask breaks Carries on the observation to GPS satellite, and will calculate and the forecast information by the infusion stands renews to the satellite information. The GPS system user is extremely covert, it is one kind of oneway system,the user only receives but does not need the transmitting message, and therefore user39。Used for setting up land marine earth measurement datum, unite and examines and surveys and draws in the ocean the highaccuracy island land。在進行了方案論證、系統(tǒng)試驗階段后，于1989 年開始發(fā)射正式工作衛(wèi)星，并于1994 年全部建成，投入使用。使用者也可免費從INTERNET網(wǎng)上取得觀測數(shù)據(jù)及梗米數(shù)據(jù)等產(chǎn)品。一般在接收機鐘確定的歷元時刻量測，保持對衛(wèi)星信號的跟蹤，就可記錄下相位的變化值，但開始觀測時的接收機和衛(wèi)星振蕩器的相位初值是不知道的，起始歷元的相位整數(shù)也是不知道的，即整周模糊度，只能在數(shù)據(jù)處理中作為參數(shù)解算。目前，GPS己經(jīng)能夠達到地殼形變觀測的精度要求， IGS常年觀測臺站己經(jīng)能構(gòu)成毫米級的全球坐標(biāo)框架。RTK 技術(shù)的關(guān)鍵在于數(shù)據(jù)處理技術(shù)和數(shù)據(jù)傳輸技術(shù)，RTK 定位時要求基準站接收機實時地把觀測數(shù)據(jù)(偽距觀測值，相位觀測值及己知數(shù)據(jù)傳輸給流動站接收機，數(shù)據(jù)量比較大，一般都要求9600 的波特率，這在無線電上不難實現(xiàn)。對于測繪領(lǐng)域， GPS衛(wèi)星定位技術(shù)己經(jīng)用于建立高精度的全國性的大地測量控制網(wǎng)，測定全球性的地球動態(tài)參數(shù)。世界才可進入將衛(wèi)星導(dǎo)航作為單一導(dǎo)航手段的最高應(yīng)用境