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
2018-05-09
100
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.
Limited geographic coverage, lack of continuous 24-hour coverage, and the limited accuracies are the disadvantages of other navigational instruments.
选项
答案
A
解析
根据题目中比较显眼的24-hour coverage可定位到A段。该段第3句所指明的全球定位系统的独特之处,对应的就是本题所说的其他导航工具的缺点,故选A。
转载请注明原文地址:https://kaotiyun.com/show/t647777K
0
大学英语四级
相关试题推荐
Peoplewholiveinheavilyindustrializedareasdonotgetasmuchsunlightastheyshould.Dust【C1】______overacityataltitud
SevenWaystoCreateaHappyHouseholdA)Everyfamilyisdifferent,withdifferentpersonalities,customs,andwaysofthink
SevenWaystoCreateaHappyHouseholdA)Everyfamilyisdifferent,withdifferentpersonalities,customs,andwaysofthink
SevenWaystoCreateaHappyHouseholdA)Everyfamilyisdifferent,withdifferentpersonalities,customs,andwaysofthink
DevelopHealthyEatingHabitsinYourChildrenA)Whatdoyouthinkyourchildrenareservedatschool?Thechildrenwereser
Thereisapopularbeliefamongparentsthatschoolsarenolongerinterestedinspelling.Thisis,however,a【C1】______.Nosch
Thereisnodenyingthatstudentsshouldlearnsomethingabouthowcomputerswork,justasweexpectthematleasttounderstand
A、FlowersandvegetablesfromDevonareonthemarketonemonthearlier.B、Farmersinthesouthwestgrowasmanyvegetablesand
A、Theundergroundoilresourceshavenotbeenaffected.B、Mostofthedesertanimalsandplantshavemanagedtosurvive.C、Theo
A、Theywanttogetcleanandhealthyfruitsandvegetables.B、Theydon’twanttodependonfarmersinruralareasanymore.C、Th
随机试题
女性,70岁,全身乏力并消瘦3个月就诊,超声检查显示脾脏弥漫性明显肿大。无外伤及肿瘤史,临床怀疑是淋巴瘤,切除脾脏送检。如果考虑恶性淋巴瘤,最常见的组织学类型是
下列关于软腭癌的放疗原则正确的是
患者,男,21岁。近2天来出现高热、乏力、腹痛腹泻,头晕1天入院。体检:脉搏90次/分,温度39.5℃,面色潮红,眼结膜充血、有出血斑且水肿,皮肤有小的出血点,血压65/45mmHg,白细胞l8×109/L,血红蛋白140g/L,尿蛋白(+++),患者休克
A.琥珀酰胆碱B.硝酸甘油C.左旋多巴D.麻黄碱E.硫喷妥钠口服无效需舌下含服的药物是
某无牙颌患者,上下颌弓位置关系正常,牙槽嵴丰满,上颌相当于3牙槽嵴唇侧尖锐骨尖。此患者在全口义齿修复前需进行
业主的付款如果逾期支付将承担延期付款的违约责任,延期付款的利息按银行贷款利率加()计算。
管道保温必须按设计规定的位置、大小和数量设置(),并填充()与保温材料相近的软质材料。
某汽车制造厂为增值税一般纳税人,生产的小汽车达到低污染排放标准,小汽车出厂价格每辆100000元(不含增值税),2c12年2月该厂购销情况如下:(1)销售给特约经销商A小汽车50辆,经销商已提取40辆小汽车,其余10辆尚未提货;该厂已经开具了
案例:下面为一道物理习题和某学生的解答过程。题目:如图8所示,质量为m、电量为q的带正电物体位于水平有界的匀强电场中,从半径为r的1/4光滑圆弧顶端由静止开始滑下,滑到圆弧底端恰好脱离电场水平飞出。竖直下落距离h时,垂直击中倾角为30°的斜面,
A、Thestewardess.B、Apassenger.C、Myfriend.D、Thepilot.A信息明示题,文章提到,whenIfeltairsickthestewardessgavemeapaperbag.由
最新回复
(
0
)