首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
GPS A) The Global Positioning System is a. space-based triangulation system using satellites and computers to measure positi
GPS A) The Global Positioning System is a. space-based triangulation system using satellites and computers to measure positi
admin
2020-01-09
40
问题
GPS
A) The Global Positioning System is a. space-based triangulation system using satellites and computers to measure positions anywhere on earth. It is first and foremost a defense system developed by the United States Department of Defense, and is referred to as the "Navigation Satellite Timing and Ranging Global Positioning System" or NAVSTAR GPS. The uniqueness of this navigational system is that it avoids the limitations of other land-based systems such as limited geographic coverage, lack of continuous 24-hour coverage, and the limited accuracies of other related navigational instruments. The high accuracies obtainable with the Global Positioning System also make it a precision survey instrument. GPS Components: the Space Segment, the Control Segment, and the User Segment.
B) The Space Segment of the system consists of the GPS satellites. These space vehicles (SVs) send radio signals from space. The GPS Operational Constellation consists of 24 satellites that orbit the earth in 12 hours. There are often more than 24 operational satellites as new ones are launched to replace older satellites. The satellite orbits repeat almost the same ground track (as the earth turns beneath them) once each day. The orbit altitude is such that the satellites repeat the same track and area over any point approximately each 24 hours (4 minutes earlier each day). There are six orbital planes (with four SVs in each), equally spaced (60 degrees apart), and inclined at about fifty-five degrees with respect to the equatorial (赤道的) plane. This constellation provides the user with between five and eight SVs visible from any point on the earth.
C) The Control Segment consists of a system of tracking stations located around the world. The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute precise orbital data and SV clock corrections for each satellite. The Master Control station uploads orbital data and clock data to the SVs. The SVs then send subsets of the orbital ephemeris (星历表) data to GPS receivers over radio signals.
D) The GPS User Segment consists of the GPS receivers and the user community. GPS receivers change SV signals into position, speed, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time distribution, and other research. Navigation in three dimensions is the primary function of GPS. Navigation receivers are made for aircraft, ships, ground vehicles, and for hand carrying by individuals. Precise positioning is possible using GPS receivers at reference locations providing corrections and relative positioning data for remote receivers. Surveying, geodetic control, and plate tectonic studies are examples.
E) Time and frequency distribution, based on the precise clocks on board the SVs and controlled by the monitor stations, is another use for GPS. Astronomical observatories, telecommunications facilities, and laboratory standards can be set to precise time signals or controlled to accurate frequencies by special purpose GPS receivers. Research projects have used GPS signals to measure atmospheric parameters.
F) At present the system consists of 24 satellites at an altitude of about 20,000 km having an orbital inclination of 55 degrees. The orbits are almost circular and it takes 12 hours for a satellite to complete a pass around the Earth. GPS signals are broadcast from a cluster of 24 or more earth orbiting satellites. Because the GPS signals are derived from the atomic frequency standards on board each satellite, they are widely used as a reference for time synchronization and frequency adjustment. The real time positioning accuracy of a single receiver is normally up to 100 meters horizontally and 150 meters vertically. However, various methods have been developed which enable much higher accuracy (centimeter level).
G) There are a variety of different types of GPS receivers on the market for commercial and public use. Prices range from $500 to $30,000, reflecting the accuracy and capabilities of the instruments. For the general outdoorsman, a good GPS receiver should have 8 satellite tracking capability and be capable of receiving the GPS satellite signals through forest covering in northern Ontario shield area; for the professional user, a minimum 8 satellite tracking capability, high memory capacity, differential GPS capability, and resistance to signal weakening under forest covering is essential; for the professional surveyor requiring high level precision and accuracy capability, they should assess the project or application for which the technology is to be used with the help of an unbiased consultant, in order to determine the most cost effective and appropriate instrument.
H) Small hand held navigational units at relatively low cost allow boaters and hikers to know their position within a few hundred meters. This accuracy is sufficient for recreational use. A hand held or similar mapping unit at mid-range price that is linked to a fixed broadcast base station. These units allow utility companies, municipalities and others to locate various items (telephone poles, waterlines, valves) with a positional tolerance of several meters. This is suitable for some Geographical Information Systems (GIS) mapping purposes.
I) GPS technology offers numerous benefits to law enforcement agencies of all types. For some agencies, the navigational capabilities offered by GPS enhance efficiency and safety. These navigational applications can be used to support a variety of policing and criminal justice functions. Other agencies use GPS positioning technologies to carry out special operations or to provide enhanced personnel safety. For example, using computerized maps of their rights given by law, cooperated with GPS, aviation personnel can determine location, speed and time.
J) The positioning capabilities offered by GPS may also contribute to the success of specialized law enforcement operations such as in controlling vehicles. One such program operated in Minneapolis led to a 60% reduction in auto theft after only one month. The automatic vehicle location systems can not only provide efficiency of response and help ensure officer safety, but also provide officer with accurate information concerning the best response route to an incident. What’s more, they can provide officers information that allows the closest patrol officers to be dispatched to a particular incident
K) Advanced Transportation Management Systems (ATMS) are heavily dependant upon GPS technology to provide data about the road system. GPS allows for law enforcement personnel to clear roadway blockages to ensure the safety of motorist. Most people associate law enforcement with the prevention, reduction, and prosecution of criminal activity. In fact, a large portion of local law enforcement resources are involved in facilitating the movement of people and vehicles in a safe manner. In conclusion, large-volume commercial applications such as cellular phones, personal communication systems, and in-vehicle navigation systems will fuel continued development of these technologies. What was ultimately the domain of the Department of Defense is rapidly becoming available for business, private, and general government use. Policing and public safety in general, will benefit from these market forces. It is clear that there are a number of GPS applications for policing.
The prices of various GPS receivers are determined by their accuracy and capabilities.
选项
答案
G
解析
根据本题的对象GPS receivers定位到H段,该段第2句的分词结构reflecting明确表明不同价位反映出相应的准确度和性能,意即准确度和性能决定了接收器的价格,故选G。
转载请注明原文地址:https://kaotiyun.com/show/vFp7777K
0
大学英语四级
相关试题推荐
Bilingual(双语的)educationinschoolshaslongbeenapoliticalhotpotato—itwasbannedinCaliforniabya1998ballotmeasure,wh
Bilingual(双语的)educationinschoolshaslongbeenapoliticalhotpotato—itwasbannedinCaliforniabya1998ballotmeasure,wh
Gesturesaren’ttheonlyareainwhichtheunwarytravelercangettrippedup.Foreignculturesadheretodifferentbusinesscus
Gesturesaren’ttheonlyareainwhichtheunwarytravelercangettrippedup.Foreignculturesadheretodifferentbusinesscus
Themassmediaisabigpartofourculture,yetitcanalsobeahelper,adviserandteachertoouryounggeneration.Themass
Cuttingtoxiclevelsofcityairpollutiontosaferlevelsissimple,butnoteasy—itrequiresresolve.Yet,despitethekeycul
Intoday’sworld,onlinesocialmediahasbecomemorepowerfulandthemostdestructivethingoverworldwide.Althoughwithtime
Threekeyfactsaboutrisingsealevelsneedtobepointedouttotheworld’spoliticiansandplanners:sea-levelriseisnowin
Likeaneedleclimbingupabathroomscale,thenumberkeepsrising.In1991,15%ofAmericanswereobese(肥胖的);by1999,thatp
随机试题
陈亮,字同甫,号龙川,学者称__________。词集名《__________》。
A.EPOB.G-CSFC.TNFD.TPOE.IFN促进血小板生成的细胞因子是
可出现双侧瞳孔针尖样缩小的是
水泥混凝土板浇筑经振捣、整平、压光后,应沿横坡方向拉毛或采用机具压槽,城市道路拉毛、压槽深度应为()。
某送变电工程的单项合同总价为()万元,该工程为大型项目。
下列关于证券自营业务的说法中,正确的是()。Ⅰ.自营业务证券公司自主买卖证券,所以具有确定的收益Ⅱ.证券自营买卖的对象有股票、债券、权证等Ⅲ.证券自营业务有交易的风险性Ⅳ.自营业务是证券公司以盈利为目的、为自己买卖证券,通过买卖价差获利
()是指在运输工具纯运行时间内平均每小时行驶的公里数。
甲和乙共同出资购买了一间房并出租给丙,租房期间甲欲转让自己的份额,乙和丙均表示愿意购买,应()。
我国有工商银行、农业银行、中国银行、建设银行四大国有大型银行。作为首家四大国有银行半年报,建行财报显示,该公司2010年上半年利润总额达到921.94亿元,较上年同期增长27.22%;归属于母公司的净利润707.79亿元,相当于平均每天赚四个亿,成为到
甲、乙合伙开办健身中心,二人在2014年12月1日约定:甲以健身场地出资,乙以现金80万元出资,合伙期限为2015年1月1日至2019年12月31日。利润双方平分。协议签订后,甲为提供健身场地,以个人名义租赁了丙的经营性用房。租期为自2015年1月1日起
最新回复
(
0
)