首页
登录
职称英语
Narrator Listen to part of a lecture about GPS. Now get ready to ans
Narrator Listen to part of a lecture about GPS. Now get ready to ans
游客
2024-01-04
45
管理
问题
Narrator
Listen to part of a lecture about GPS.
Now get ready to answer the questions. You may use your notes to help you answer. [br] What does the professor mean when he says this?
What is GPS? Its full name is the Global Positioning System and a satellite-based navigation system. Generally speaking, it is made up of a network of 24 satellites placed into orbit by the U. S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. Nowadays, GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.
How does it work? At first, GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. Secondly, GPS receivers take this information and use triangulation to calculate the user’s exact location. Essentially, the GPS receiver compares two times, one is the time a signal was transmitted by a satellite; the other is the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user’s position and display it on the unit’s electronic map.
A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position and track movement. With four or more satellites in view, the receiver can determine the user’s 3D position, here three dimensions are latitude, longitude and altitude. Once the user’s position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.
How accurate is GPS? Today’s GPS receivers are extremely accurate, thanks to their parallel multi-channel design. Garmin’s 12 parallel channel receivers are quick to lock onto satellites when first turned on and they maintain strong locks, even in dense foliage or urban settings with tall buildings. Certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers. Garmin GPS receivers are accurate to within 15 meters on average.
How about the Newer Garmin GPS receivers? With WAAS, that is Wide Area Augmentation System, its capability can improve accuracy to less than three meters on average. No additional equipment or fees are required to take advantage of WAAS. Users can also get better accuracy with Differential GPS, which corrects GPS signals to within an average of three to five meters. The U. S. Coast Guard operates the most common DGPS correction service. This system consists of a network of towers that receive GPS signals and transmit a corrected signal by beacon transmitters. In order to get the corrected signal, users must have a differential beacon receiver and beacon antenna in addition to their GPS.
GPS satellites are powered by solar energy. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there’s no solar power. Small rocket boosters on each satellite keep them flying in the correct path.
Here are some other interesting facts about the GPS satellites, also called NAVSTAR by the official of U. S. Department of Defense. the first GPS satellite was launched in 1978; a full constellation of 24 satellites was achieved in 1994; each satellite is built to last about 10 years. Replacements are constantly being built and launched into orbit; A GPS satellite weighs approximately 2000 pounds and is about 17 feet across with the solar panels extended; transmitter power is only 50 watts or less.
选项
A、GPS is very useful in military and civilian fields.
B、GPS is very good at data calculation.
C、GPS is a modern way to transit signals.
D、It is very difficult for GPS to determine position.
答案
A
解析
本题为语用理解题中的功能题,考查考生是否能够弄清听力材料中说话者是如何运用语言来表达其意图的,如说话者的目的等。题目问:教授说下面一段话是什么意思?第三段指出GPS通过对物体的定位可以计算出物体速度、方位角、轨迹等数据,目的是接上文说的GPS在军事和民事方面都有重要用途,因此不难判断出选项A为正确答案。
转载请注明原文地址:http://tihaiku.com/zcyy/3332009.html
相关试题推荐
TheTreloarValleypassengerferry[br][originaltext]Narrator:Youwillhearp
TheTreloarValleypassengerferry[br][originaltext]Narrator:Youwillhearp
TheTreloarValleypassengerferry[originaltext]Narrator:Youwillhearpartof
Listentothedirectionsandmatchtheplacesinquestions11-15totheappropri
Listentothedirectionsandmatchtheplacesinquestions11-15totheappropri
Choosethecorrectletter,A,BorC.[br]Thelecturewasorganisedby[origina
Choosethecorrectletter,A,BorC.[br]Whydidthelecturerchoosetofocus
Listentothedirectionsandmatchtheplacesinquestions11-15totheappropri
Choosethecorrectletter,A,BorC.[br]Thelecturewasorganisedby[origin
Choosethecorrectletter,A,B,orC.[br]【L38】[originaltext]Nowlistencaref
随机试题
Youwillhearaninterviewaboutdifferentmoneytypesinorder:guardians,idea
Increasingnumbersofpeoplehavemigratedfromthecountrysideandmovedinto
Mostpeopleareawarethatoutdoorairpollutioncandamagetheirhealth,bu
企业享受的下列税收优惠中,属于企业会计准则规定的政府补助的是( )。A.增值税的
某工作计划进度与实际进度如下图所示,从图中可获得的正确信息有( )。 A
在进行供应商绩效管理时,应遵循的基本原则不包括()。A.持续进行 B.实行淘
李某购买了其亲戚家的一处不动产。按照有关规定,李某应到当地房地产管理部门办理(
如图6所示,一高度为30m的塔结构,刚性连接设置在宽度b=10m,长度h=11m
关于违约责任,下列说法错误的是( )。A.违约责任的承担形式包括违约金责任
根据《施工合同标准文本》的规定,监理人在施工合同履行中()。A.是独立的第三方
最新回复
(
0
)