全球定位系統(tǒng)（Global Positioning System）

簡單地說，這是一個由覆蓋全球的24顆衛(wèi)星組成的衛(wèi)星系統(tǒng)。這個系統(tǒng)可以保證在任意時刻，地球上任意一點都可以同時觀測到4顆衛(wèi)星，以保證衛(wèi)星可以采集到該觀測點的經(jīng)緯度和高度，以便實現(xiàn)導(dǎo)航、定位、授時等功能。這項技術(shù)可以用來引導(dǎo)飛機、船舶、車輛以及個人安全地、準(zhǔn)確地沿著選定的路線，準(zhǔn)時到達(dá)目的地。

全球定位系統(tǒng)(GPS)是20世紀(jì)70年代由美國陸?？杖娐?lián)合研制的新一代空間衛(wèi)星導(dǎo)航定位系統(tǒng) 。其主要目的是為陸、海、空三大領(lǐng)域提供實時、 全天候和全球性的導(dǎo)航服務(wù)，并用于情報收集、核爆監(jiān)測和應(yīng)急通訊等一些軍事目的，是美國獨霸全球戰(zhàn)略的重要組成。經(jīng)過20余年的研究實驗，耗資300億美元，到1994年3月，全球覆蓋率高達(dá)98%的24顆GPS衛(wèi)星星座己布設(shè)完成。

對目的地及周邊環(huán)境的精準(zhǔn)查詢需求帶動了GPS導(dǎo)航產(chǎn)品市場的繁榮。據(jù)相關(guān)統(tǒng)計，歐美國家導(dǎo)航設(shè)備普及率達(dá)到90%，日本更是超過95%。一項對3G應(yīng)用的展望和創(chuàng)意的專業(yè)調(diào)查顯示，17.79%的被調(diào)查者選擇了3G網(wǎng)絡(luò)視頻對話，15.34%的被調(diào)查者選擇了GPS/地圖搜索，在3G時代來臨之際，人們對GPS/電子地圖的關(guān)注，足以顯現(xiàn)它在日常生活中的重要性。

拓展閱讀：

Mr. Perkin's New Car

Mr. Perkin stood at the bus-stop and watched the cars go by. Many of the cars were new Beta 400s, and most of them were yellow. Mr. Perkin always wore the same clothes as other men, ate the same food as other people, and did the same things after work, and at the end of the week, Mr. Perkin did not like to be different.

The following week, Mr. Perkin bought a new, bright yellow Beta 400s. He was satisfied with it, and drove it to work in the very next day. He was even more satisfied with his new car, when he saw all the other Beta 400s, in front, behind, and on both sides of him.

Mr. Perkin parked his car in a big car-park near his office, and walked the rest of the way. But when he came back at five o'clock, there were so many bright yellow Beta 400s. He tried his key in some of the cars, but people passing by gave him a look he didn't like. So he stopped. Poor Mr. Perkin had to wait nearly two hours until his was the only yellow Beta 400s in the car-park.

1. Mr. Perkin bought a new, bright yellow_______.

A. Beta 600s B. Beta 400a C. Beta 400s D. Beta 600a

2. Mr. Perkin did not like to be_______.

A. different B. foolish C. strange D. fashionable

3. Poor Mr. Perkin had to wait ______hours until found his car.

A. two B. nearly two C. three D. five

4. Why does Mr. Perkin want a new yellow Beta 400s?

5. How did Mr. Perkin find his car?

答案：

1. C

解析：Mr. Perkin bought a new, bright yellow Beta 400s 選C

2. A

解析：Mr. Perkin did not like to be different. 選A

3. B

解析：Poor Mr. Perkin had to wait nearly two hours until his was the only yellow Beta 400s in the car-park 選B

4. (Because he likes to do the same things as other people.)

解析：Mr. Perkin did not like to be different.

5. (Mr. Perkin couldn't find his car until his was the only yellow Beta 400s in the car-park.)

解析：Poor Mr. Perkin had to wait nearly two hours until his was the only yellow Beta 400s in the car-park

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