【正文】 [15]數(shù)據(jù)記錄。[12]的NMEA標(biāo)準，國家海洋電子協(xié)會，7里格斯大街，錫弗納帕克醫(yī)師21146，[13] GPSMAP 60CSX用戶指南。山口247。的WAAS / EGNOS的準備2芯片GPS芯片組。9499。[8]，應(yīng)用衛(wèi)星導(dǎo)航使用全球定位系統(tǒng)，伽利略，以及增強系統(tǒng)，澳特豪斯出版社（2005年）。[7]微分差分全球定位系統(tǒng)。[6]二霍夫曼 Wellenhof和全球定位系統(tǒng)閣下Lichtenegger：理論與實踐（第5版。[5] ，了解GPS：原則和應(yīng)用（第2版。[3]屬萊瑟姆，全球定位系統(tǒng)變得非常簡單，使用在戶外（第四版全球定位系統(tǒng)。），恒河賈木納河出版社（2006年）。2顯示了一部分的NMEA語句時獲得一個Garmin GPSMAP 60CSX型GPS接收機[13]連接，如HYPERTERM的[到一個PC機的串行端口和一個串行通信方案14]是在PC上啟動，并顯示接收的數(shù)據(jù)從串行端口。通常的NMEA語句發(fā)出每秒。從一個GPS接收器的數(shù)據(jù)輸出是ASCII文本格式并兼容的NMEA 0183，或干脆的NMEA格式[12]。這個輸出數(shù)據(jù)通常是串行格式和通信協(xié)議符合RS232串行標(biāo)準。除了GPS差分數(shù)據(jù)RTCM接口，一些較先進的全球定位系統(tǒng)接收器包括的WAAS / EGNOS的改正的硬件和軟件，以改善基本GPS接收機的精確度。全球定位系統(tǒng)接收器，可包括為差分輸入差分全球定位系統(tǒng)校正，作為GPS差分數(shù)據(jù)RTCM（無線電技術(shù)委員會海事服務(wù)）已知的接口[11]。商業(yè)GPS接收機是一個小型電池供電的便攜式裝置，接收來自GPS衛(wèi)星的信號，然后顯示用戶的位置，高度，速度，航向，和幾個其他導(dǎo)航參數(shù)。這些電視臺不斷監(jiān)察所有GPS衛(wèi)星的運行狀態(tài)，并在車上同步原子鐘內(nèi)互相幾納秒的衛(wèi)星，并調(diào)整每個衛(wèi)星的軌道模型。隨著衛(wèi)星的數(shù)量增加，可靠性和整體系統(tǒng)的可用性得到了提高。GPS系統(tǒng)由三個主要部分組成：空間段，控制段和用戶段。兼容的GPS接收器可以接收WAAS / EGNOS的校正信號，并計算其立場，以一個約35米的精度在此對差分全球定位系統(tǒng)技術(shù)的優(yōu)點是有沒有額外費用的用戶，因為所需的硬件和軟件都將GPS接收機內(nèi)置在一個非常小的額外費用。這種技術(shù)最早是在美國，并作為廣域增強系統(tǒng)（WAAS的）已知。 圖1顯示是差分糾正系統(tǒng) 另一種方法來提高GPS系統(tǒng)精度轉(zhuǎn)發(fā)“更正”GPS衛(wèi)星定位系統(tǒng)校正訊號[8] ，[9]和[10]。1顯示了一個典型的差分全球定位系統(tǒng)實施布局。差分全球定位系統(tǒng)的精度與索取的水平取決于許多因素，如該基準站的GPS接收機和用戶的質(zhì)量，和大氣條件。這對每個跟蹤衛(wèi)星錯誤信號形成一個更正確的信息，并傳輸?shù)浇邮掌胀ǖ腉PS系統(tǒng)。差分全球定位系統(tǒng)的工作原理是放置在一個地球上（參考站）的已知位置正是一個高性能的GPS接收機。GPS信號定位精度可顯著提高是由于利用差分GPS（DGPS）已知的技術(shù)。在典型的應(yīng)用有可能獲得至少6或7顆衛(wèi)星在一個有清晰的空中視野的地方信號。通常情況下，三顆衛(wèi)星都必須準確地計算出地球表面的4顆衛(wèi)星的一個點的位置，必須計算高度以及。該衛(wèi)星軌道是地球上空約20,000表面和衛(wèi)星公里，定位，使他們傾向于與一個55度角赤道。 最初，民用全球定位系統(tǒng)的精度是故意擾亂使用方法稱為選擇可用性（SA）。這個系統(tǒng)是實施軍事目的，并提供導(dǎo)航數(shù)據(jù)修復(fù)大約每隔一小時，并沒有非常準確的。街道地圖 全球定位系統(tǒng)（GPS）是一種基于衛(wèi)星的導(dǎo)航系統(tǒng)[1]，[2] [3],[4] ,[5],由美國國防部開發(fā)部。該裝置收集在一個文件中的用戶協(xié)調(diào)上的SD卡，然后在谷歌地圖軟件是用來繪制了關(guān)于一個街道地圖用戶的軌道。與早期的GPS系統(tǒng)的問題之一是它的精度低，妨礙它在應(yīng)用中使用，如需要高準確度試驗和街頭路線的指導(dǎo)。m. The advantage of this technique over the dGPS is that there is no additional cost to the user since the required hardware and software are built into the GPS receiver at a very small extra cost. One disadvantage of this technique is that it may be difficult to receive correction signals at higher latitudes, away from the Equator. The GPS system consists of three major parts: Space segment, Control segment, and User segment. The Space segment consists of the orbiting satellites, and as of March 2008, there were 31 actively broadcasting satellites in the GPS constellation. With the increased number of satellites, the reliability and availability of the overall system has been improved. The Control segment consists of the monitoring stations located on Earth. These stations constantly monitor the operational status of all the GPS satellites and also synchronize the atomic clocks on board the satellites to within a few nanoseconds of each other, and adjust the orbital model of each satellite. The User segment consists of the user GPS receivers. A mercial GPS receiver is a small battery operated portable device that receives signals from the GPS satellites and then displays user’s position, altitude, speed, heading, and several other navigational parameters. Some sophisticated receivers also incorporate streetlevel maps where the position of the user is shown dynamically in realtime on a map. GPS receivers may include an input for differential dGPS corrections, known as the RTCM (The Radio Technical Commission for Maritime Services) interface [11]. As mentioned earlier this interface improves the accuracy of the receiver considerably. In addition to the RTCM interface, some more sophisticated GPS receivers include WAAS/EGNOS correction hardware and software to improve the accuracy of the basic GPS receiver. GPS receivers also produce RS232 patible serial output data known as NMEA (National Marine Electronics Association) sentences which enable them to be connected to a PC (or a similar equipment) to relay the navigational data such as the latitude, longitude, altitude, speed, heading and so on. This output data is usually in serial format and the munication protocol conforms to the RS232 serial standards. The default serial munication parameters of most GPS receivers are set as follows: 4800 Baud, 8 data bits, no parity bit, and 1 stop bit. The data output from a GPS receiver is in ASCII text format and is patible with the NMEA 0183, or simply the NMEA format [12]. According to this format, navigational information are sent in the form of “sentences” where each NMEA sentence starts with a “$” sign, the navigational parameters are separated by mas, and each sentence is terminated with two hexadecimal checksum characters. The NMEA sentences are usually sent out every second. Fig. 2Fig. 2 shows part of the NMEA sentences obtained when a Garmin GPSMAP 60CSX type GPS receiver [13] is connected to the serial port of a PC and a serial munication program such as the HyperTerm [14] is activated on the PC to display the data received from the serial port. References[1] P. Misra and P. Enge, Global positioning system: signals, measurements amp。. By this arrangement it is guaranteed that at least four satellites are visible at any point on Earth at any time. Normally, three satellites are required to calculate the position of a point accurately on Earth’s surface and four satellites are required to calculate the altitude as well. Thus, with the arrangement of the satellites it is possible to calculate both the position and the altitude of any point on Earth’s surface typical applications it is possible to get signals from at least six or seven satellites in a place with a clear view of the sky. In general, the accuracy is increased as more satellites are used in the position and altitude calculations. The position accuracy of a GPS signal can be improved significantly usi