【導(dǎo)讀】進(jìn)的導(dǎo)航定位系統(tǒng)，已在很多領(lǐng)域得到廣泛應(yīng)用。其在測繪領(lǐng)域中的應(yīng)用更是。較傳統(tǒng)測繪手段的一次飛躍。在一些基礎(chǔ)測量項(xiàng)目、水利工程或其他工程建設(shè)實(shí)。施前，通常要進(jìn)行野外實(shí)地查勘或工程測繪?；蛘甙巡榭钡降膶?shí)物標(biāo)志標(biāo)注到已有的測圖中，或者需要近似。測出查勘點(diǎn)的平面位置和高程。依據(jù)資料尋找實(shí)物標(biāo)志，過去主要依賴有關(guān)當(dāng)事。對于生疏之地，往往費(fèi)工費(fèi)時且收效甚微。較為準(zhǔn)確和及時地標(biāo)注到地圖上，更是難以實(shí)現(xiàn)。在中小比例尺測繪或航測調(diào)繪。采用常規(guī)儀器法施測，作業(yè)效率低且難度大。定位施測就能很好地解決這些問題，且更為快捷和準(zhǔn)確。手持GPS以其攜帶方。點(diǎn)、收資等)中應(yīng)用非常方便。精度同樣能達(dá)到5-10米。本文就此內(nèi)容展開研究。GPS定位的基本方法.........

　　

【正文】 he two global satellite navigation systems currently operating, the GPS has gained preference in most international markets. The operation of the GPS relies on signals received from 24 NAVSTAR satellites, each of which orbit in space about 11,000 miles above the earth’s surface. These satellites revolve around the earth twice a day (or once every 12 hours) and transmit signals to GPS receivers positioned on or above the earth’s surface. GPS receivers, which process data emitted from GPS satellites, pare the time the satellite signal was transmitted with the time the signal reaches the receiver. The receiver is then able to determine its precise distance from the satellite. . Government Policies On March 29, 1996, the President of the United States approved a prehensive national policy on the future management of the GPS and related . Government augmentations. The policy seeks to enhance the country’s productivity and economic petitiveness while protecting . national security and foreign policy interests. Based on remendations from the Departments of Defense, 華北水利水電學(xué)院畢業(yè)設(shè)計(jì)（論文） 27 Transportation, and State, the policy requires the President to make annual determinations regarding certain GPS operational functions. Global Industry and Markets Japan, followed by the United States, is the principal global supplier of GPSrelated products. In 1998, Japan accounted for 47 percent ($ billion) of the global GPS market, whereas the United States represented 32 percent ($ billion). Eighteen percent ($784 million) of the remaining market share was largely accounted for by European countries. Although the United States and Japan are parable with respect to GPS manufacturing technology, the United States is generally believed to enjoy a slight lead in higher valueadded products with an advanced software content. Global demand for GPS products grew significantly during 19972020, with total global sales of such products increasing by 275 percent to $ billion. Car navigation, which is the largest international market for the GPS, accounted for 34 percent ($ billion) of total global GPS sales in 2020. The consumer sector, which is the second largest market, represented 22 percent ($ billion) of such sales. The third largest market sector, surveying and mapping, accounted for 16 percent ($ billion) of global sales in 2020. Rising sales were recorded in all market sectors during 19972020, and are projected to continue upward during 202003. Global Developments GPS receivers are available at a fraction of the price of a decade ago. Current prices of GPS receivers may range from approximately $100 for a small, onehand operated 12 channel receiver to $2,000 for a deluxe color automobile GPS receiver capable of displaying routes and giving turnbyturn directions and voice prompts to drivers. Prices of receivers designed for avionics, military equipment, and other sophisticated applications may by higher. Car navigation systems are continuing to grow in popularity in Asia, with Japan leading in output (about million units shipped in 2020) and product innovation. While CDROMs have been an essential software for car navigation, DVDROMs are now being used extensively. 華北水利水電學(xué)院畢業(yè)設(shè)計(jì)（論文） 28 Certain European countries, especially in Scandinavia, are taking a more entrepreneurial approach to GPS technology by focusing on immediate applications in land survey, vehicle tracking, geographic information systems, and coastal navigation. In some instances this has led to the acquisition of . firms or technology, such as the transfer of the Magnavox’s GPS product line to the Swiss firm Leica. Forecast Rapidly expanding GPS technology will continue to provide both . and foreign users with tremendous capabilities in consumer, mercial, industrial, and military applications. Worldwide sales of GPS products are projected to total nearly $ billion by 2020, with products accounting for 30 percent ($ billion) of those sales. The next generation of GPS satellites, which are scheduled to be launched by 2020, will have increased flexibility to acmodate new augmentations and auxiliary payloads, and larger processor and memory capacity. Introduction The Global Positioning System (GPS), which originated in the United States in the late 1970s, is widely recognized as the world’s most accurate method of navigation. The GPS is also well known for precision time signals that synchronize global information work systems utilizing fiber optics, satellites, radio, coaxial cable, and copper wire. Being an embedded technology, the GPS is not generally visible in personal puters, automobiles, surveying equipment, weather tracking systems, military munitions, electronic receivers, and other products incorporating the technology. Most individuals, for example, are unaware that data received from domestic and international financial institutions are dependent on the accurate synchronization of data streams provided by the GPS. Since its creation by the . Department of Defense almost 25 years ago (at a cost of about$12 billion)4 and its emergence into broader public awareness subsequent to being available for civilian use in 1984, the GPS has evolved into a wide range of technologies that have provided an enormous range of benefits for consumers. For example, numerous police, fire, and emergency medical services have incorporated the GPS into vehicles to ensure the quickest possible response in lifeordeath situations. Automobile 華北水利水電學(xué)院畢業(yè)設(shè)計(jì)（論文） 29 manufacturers offer GPSaided map displays that give directions to drivers on display screens and through synthesized voice instruction. The GPS has proven to be invaluable to hikers, golfers, cyclists, and other recreational users by providing precise directions. The system is likely to be incorporated into cellul