测绘工程专业英语(20-30)
测绘工程专业英语全文翻译（Unit20~30）
Unit 20 Understan ding the GPS（认识GPS）
What Is GPS?（什么是GPS）
The global Positioning System (GPS) operated by the U .S. Department OF Defense (DOD)is a satellite-based system that can be used to locate positions anywhere on the earth（.全球定位系统（GPS），由美国国防部管理，是一个基于人造卫星的系统，可以用来在全球任何地方定位）GPS provides continuous (24 hours/day), real-time, 3-dimensional positioning, navigation and timing worldwide.（GPS 提供全世界范围内的全天候，实时，三维坐标，导航和授时的功能。）Any person with a GPS receiver can access the system, and it can be used for anyapplication that requires location coordinates.（任何拥有一台GPS 接收机的人都可以使用这套系统，可以应用于任何需要位置坐标的工作中）The GPS system consists of three segments: ⑴the space segment: the GPS satellitesthemselves, ⑵the control segment, operated by the U .S. military, and ⑶the user segment,which includes both military and civilian users and their GPS equipments（.GPS 由三个部分组成：⑴太空部分：GPS 卫星自己，⑵地面控制部分，由美国军方控制，⑶用户部分，包括军方和民用用户和他们的装备。）Space Segment: The GPS Constellation（太空部分：GPS 星座）The first GPS satellite was launched by the U .S. Air Force in early 1978.（第一颗GPS 卫星由美国空军在1978 年的早些时候发射的）There are now 24 satellites orbiting the earth at an altitude of about 10,900 miles.（现在有24 颗卫星在绕地球大约10900 英里的高度运行）The high altitude insures that the satellite orbits are stable, precise and predictable, and that the satellites’ motion through space is not affected by atmospheric drag.（这么高的高度确保了卫星轨道是稳定、精确和可知的，并且确保了卫星穿过太空的运行不受到大气阻力的影响）There are four satellites in each of 6 orbital planes.（6 个轨道平面中每个有4 颗卫星。）Each plane is inclined 55 degrees relative to the equator, which means that satellites crosstie equator tilted at a 55 degrees angle.（每个平面相对于赤道面倾斜55 度，这就意味着这些卫星以55 度角穿过赤道）The system is designed to maintain full operational capability even if two of the 24satellites fail.（这套系统被设计成即使24 颗卫星的 2 颗故障也能维持全工作能力）These 24 satellites make up a full GPS constellation.（这24 颗卫星组成了一个完整的GPS 星座）The GPS satellites are powered primarily by sun-seeking solar panels, with nicad batteries providing secondary power.（GPS 卫星主要由太阳定向太阳能电池板提供动力，镍镉蓄电池提供备用动力）Each GPS satellite has four atomic clocks on board, only one of which is in use at a time. These highly accurate atomic clocks enable GPS to provide the most accurate timing system that exists. （每一个GPS 卫星有四个原子钟，某一时刻只有一台在使用。这些高精度原子钟能够使GPS 提供最准确的时间系统）Control Segment: U.S. DOD Monitoring（控制部分：美国国防部监控）The U .S. Department Of Defense maintains a master control station at Falcon Air Force Base in Colorado Springs.（美国国防部维持了一个主控站，在科罗拉多斯普林斯的佛肯空军基地）There are four other monitor stations located in Hawaii, Ascension Island, Diego Garcia and Kwajalein.（还有4 个监控站座落在夏威夷、阿松森岛、迭哥加西亚岛、卡瓦加兰岛）The DOD stations measure the satellite orbits precisely.（DOD 站精确测量卫星轨道）Any discrepancies between predicted orbits and actual orbits are transmitted back to the satellites.（任何预报轨道和实际轨道之间的偏差被传回卫星。）The satellites can then broadcast these corrections, along with the other position and timing data, so that a GPS receiver on the earth can precisely establish the location of each satellite it is tracking.（然后卫星可以广播这些改正值——连同位置和时间数据一起，以便地球上的GPS 接收机可以精确确定它所跟踪的每个卫星的位置）User Segment: Military and Civilian GPS Users （用户部分：军方和民用GPS 用户）The U .S. military uses GPS for navigation, reconnaissance, and missile guidance systems.（美国军方把GPS 用在导航、侦察和导弹制导系统上Civilian use of GPS developed at the same time as military uses were being established, and has expanded far beyond original expectations.（GPS 的民用在军用建立起之时就发展起来了，并且已经发展的远远超过起初的期望）There are civilian applications for GPS in almost every field, from surveying to transportation to natural resource management to agriculture.（GPS 的民用用途几乎用在每个领域，从测量到交通到自然资源管理到农业）Most civilian uses of GPS, however, fall into one of three categories: navigation, positioning and timing.（然而，GPS 的大部分民
用用途，分为三种类型：导航、定位和授时。）
How Does GPS Work?（GPS 如何工作）
A GPS receiver calculates its position by a technique called satellite ranging, which involves measuring the distance between the GPS receiver and the GPS satellites it is tracking.（GPS 接收机利用一项被称为卫星测距的技术，计算它自己的位置，涉及到GPS 接收机到它所跟踪的GPS 卫星的距离测量）The range (the range a receiver calculates is actually a pseudorange, or an estimate orange rather than a true range) or distance is measured as elapsed transit time.（距离（接收机测的距离实际上是伪距，或者说是距离估值，而不是真实距离）是用传播时间来测的）The position of each satellite is known, and the satellites transmit their positions as part of the “ messages” they send via radio waves.（每个卫星的位置已知，并且卫星将它们的位置作为它们用无线电波发出的“讯文”的一部分传送出去）The GPS receiver on the ground is the unknown point, and must compute its position based on the information it receives from the satellites.（地面GPS 接收机是未知点，必需基于它从卫星收到的这些信息计算它的位置。）The first step in measuring the distance between the GPS receiver and a satellite requires measuring the time it takes for the signal to travel from the satellite to the receiver.（测量GPS 接收机和卫星的第一步，要求测出从卫星到接收机的信号传播时间。）Once the receiver knows how much time has elapsed, the travel time of the signal multiplies the speed of light (because the satellite signals travel at the speed of light, approximately 186,000 miles per second) to compute the distance.（一旦接收机知道用了多少时间，用信号的传播时间乘上光速（因为卫星信号以光速传播，大约186,000 英里每秒）来计算距离。）Distance measurements to four satellites are required to compute a 3-dimensional (latitude, longitude and altitude) position.（计算一个三维（纬度、精度和高程）位置需要4 颗卫星的距离值）
In order to measure the travel time of the satellite signal, the receiver has to know when the signal left the satellite and when the signal reached the receiver.（为了测出卫星信号的传播时间，接收机需要知道信号是什么时候离开卫星的和什么时候到达接收机的）Knowing when the signal reaches the receiver is easy, the GPS receiver just “ checks” its internal clock when the signal arrives to see what time it is（.确定信号到达接收机的时间容易，GPS 接收机只需在信号到达时“检查”自己内置的钟，看看是什么时间）But how does it “know” when the signal left the satellite?（但是怎样“知道”信号何时离开卫星的呢？）All GPS receivers are synchronized with the satellites so they generate the same digital code at the same time.（所有GPS 接收机与卫星是同步的，因此它们在同一时间产生同样的信号码）When the GPS receiver receives a code from a satellite, it can look back in its memory bank and “remember” when it emitted the same code（.当GPS 接收机收到一个从卫星来的码时，它可以在它的内存条中回忆并“记起”它发出的相同码）This little “ trick” allows the GPS rece iver to determine when the signal left the satellite.（这个小小的“技巧”使得GPS 接收机能够确定信号是何时离开卫星的）Once the receiver has the distance measurements, it’s basically a problem of geometry（.一旦接收机测出了距离，基本上就只有几何上的问题了）If it “ knows” where the four satellites are, and how fa r it is from each satellite, it can compute its location through trilateration. Here’s an illustration of how it works.（如果知道了4 颗卫星的位置，距每颗卫星的距离，就可以通过三边测量来计算它的位置。这里有个例子说明它如何工作的）The GPS receiver “ locks on” to one satellite and calculates the range to be 12,000 miles.（GPS 接收机“锁定”一颗卫星并计算出距离为12,000 英里）This fact helps narrow the receiver location down, but it only tells us that we are somewhere on a sphere which is centered on the satellite and has a 12,000 mile radius.（这把接收机的位置限定下来，但是它只能告诉我们在一个以这个卫星为中心，半径12,000 英里的球面上）Many of the locations on that sphere are not on earth, but out in space.（这个球面的许多位置不在地球上，而在太空中）Now,consider that the receiver picks up a signal from a second satellite and calculates the range between the receiver and the satellite to be 10,000 miles.（现在，考虑这个接收机从第二颗卫星获得一个信号，计算出接收机到这颗卫星的距离是10,000英里）That means we are also somewhere on a sphere with a 10,000 mile radius with the second satellite at the center.（这就意味着我们也在一个以第二颗卫星为中心、半径10,000 英里的球面上的某处）We must, therefore, be somewhere where these two spheres intersect.（因此，我们肯定在这两个球面相交的某处。）When the two spheres intersect, a circle is formed, so we must be somewhere on that circle.（当这两个球面相交时，一个圆圈形成了，因此我们肯定在这个圆圈的某处）If the receiver picks up another satellite, says at 11,000 miles
away, another sphere is formed, and there are only two points where the three spheres intersect.（如果接收机“拾取”了另一个卫星，比方说11,000 英里以外，另一个球面形成了，三个球面相交只有两个交点）Usually the receiver can discard one of the last two points because it is nowhere near the earth.（通常接收机可以丢弃最后这两点中的一个点，因为它离地球差的远）So, w e’re left with one point which is the location of the GPS receiver.In practice, a fourth measurement is needed to correct for clock error（.这样我们留下一个点，它是GPS 接收机的位置。在实际当中，需要第四个观测值来修正时间误差）
Uuit21 Understanding the GPS (II) 认识GPS(II)
GPS Error Sources (GPS 误差来源)There are many sources of possible errors that will degrade the accuracy of position computed by a GPS receiver.（有许多或然误差来源，这种误差会降低GPS 接收机计算的位置的准确度）The travel time of GPS satellite signals can be altered by atmospheric effects; when a GPS signal passes through the ionosphere and troposphere it is refracted, causing the speed of the signal to be different from the speed of a GPS signal in space.（GPS 卫星信号的传播时间会因大气影响而改变；当GPS 信号穿过电离层和对流层时会发生折射，因为信号速度与在太空中信号的速度不同。）Sunspot activity also causes interference with GPS signals（.太阳黑子活动也对GPS 信号产生干扰）Another source of error is measurement noise, or distortion of the signal caused by electrical interference or errors inherent in the GPS receiver itself.（另一个误差源是测量噪声，或者是由于电干扰或GPS 接收机自己固有的误差引起的信号失真）Errors in the ephemeris data (the information about satellite orbits) will also cause errors in computed positions, because the satellites weren’ t really where the GPS receiver “thought” they were (based on the information it received) when it computed the positions.（星历数据（关于卫星轨道的信息）误差也会引起位置的误差，因为当计算位置时，卫星不真正地在接收机“认为”它们在的地方（基于它接受的信息所知道））Small variations in the atomic clocks (clock drift) on board the satellites can translate to large position errors; a clock error of 1 nanosecond translates to 1 foot or 0 .3 meters user error on the ground.（卫星原子钟内的很小的变化（钟漂）能转化成很大的位置误差；一纳秒的钟差能造成 1 英尺或0.3 米的地面用户误差）Multi path effects arise when signals transmitted from the satellites bounce off a reflective surface before getting to the receiver antenna.（当从卫星发射的信号在到达接收机天线之前，被一个反射面反射时，多路径效应出现了）When this happens, the receiver gets the signal in straight line path as well as delayed path(multiple paths). The effect is similar to a ghost or double image on a TV set（.当这种情况发生时，接收机接收直线路径来的信号，也接收延迟路线（多路径）来的信号。其效果与电视的重影或重像类似）How to Reduce GPS Errors（如何减小GPS 的误差）You’ve probably heard people talk about getting 2 to 5 meters accuracy with a GPS receiver, or even centimeter or millimeter accuracy（.你可能听说过有人说GPS 接收机可以达到 2 到5 米的准确度，甚至是厘米或毫米级精度）Is there a way to cancel out the errors and get satisfied accuracy?（有方法低偿误差并获得满意的精度吗？）The answer is yes, but the level of accuracy depends on the type of equipment you are using.（回答是肯定的，但是准确度的级别依赖于你使用的装备的类型）The following discussion describes a technique used to achieve 2 to 5 meters accuracy using mapping (resource) grade receivers.（下面的讨论描述了一种用于绘图（资源）级接收机的技术，能够获得 2 到 5 米的准确度）Some mapping grade receivers are even capable of sub-meter accuracy, but the increased accuracy comes at a price.（一些绘图级的接收机甚至能够达亚米级精度，但是精度的提高是以很高代价带来的Survey grade receivers are the most accurate, capable of centimeter or even millimeter accuracy, depending on the equipment, but they use more advanced techniques to achieve this level of accuracy and, naturally, are more expensive.（测地级接收机最精确，凭装备能够达到厘米甚至是毫米级精度，但是它们是使用更先进的技术才得到这样的精度水平，自然地，就更昂贵。）Recreational grade receivers usually can receive real-time differential corrections, but they cannot store a file that can be differentially corrected using post-processing methods.（休闲级的接收机通常可以接收实时差分改正，但是它们不能存储文件，以便可以用后处理方法差分改正。）Differential Correction（差分改正）
Differential correction is a method used to reduce the effects of selective available (SA) and other sources of GPS positioning error (differential correction cannot correct for multipath or receiver error; it
counteracts only the errors that are common to both reference and roving receivers).（差分改正是一种用来减小选择可用性政策(SA)影响和其它GPS 定位误差源的方法（差分改正不能修正多路径效应或接收机误差；它只能抵消基准接收机和流动接收机所共有的误差）It requires, in addition to your “ roving” GPS receiver, a GPS receiver on the ground in a known location to act as a static reference point.（这需要——除了你的“流动”GPS 接收机之外——一个GPS 接收机在地面上一个已知的位置担当参考点）
This type of setup is often called a GPS base station. Since the base station “ knows” where it is, it can compute the errors in its position calculations (in reality, it computes timing errors) and apply them to any number of roving receivers in the same general area.（这种设备经常被称为GPS 基准站。由于基准站“知道”在哪儿，它就可以计算它自己的
位置误差（实际上，它是计算定时误差），并将它们应用于将……应用于】许多同一区域的流动接收机）This requires that the base and rover receivers “ see” the same set of satellites at the same
time.（这需要基准接收机和流动接收机同时“看到”相同一批卫星）The base station, depending upon how it is configured, can correct roving GPS receiver data in one (or both) of two ways.（基准站，依照如何配置，可以用两种中的一种方法（或同时用两种）对GPS 流动接收机的数据进行修正）⑴in the first method, called real-time differential correction or real-time differential GPS (DGPS), the base station transmits (usually via radio link) error correction messages to other GPS receivers in the local area.（第一种方法，称为实时差分改正或实时差分GPS（DGPS），基准站发射（通常经由无线电联系）误差改正信息到其它当地的GPS 接收机）In this case, the positions you read on your GPS receiver while you are out collecting data are the corrected positions.（这样，当你外出收集数据时在你的GPS 接收机上读出的位置就是改正后的位置。）⑵the second method, called post-processed differential correction, is performed on a computer after the roving receiver data are collected.（第二种方法，称为后处理差分改正，在流动站数据收集完后经由计算机完成的）While you are out in the field collecting data, the positions you read on your roving GPS receiver are uncorrected.（当你在野外收集数据时，你在GPS 流动接收机上读出的位置是未经修正的）It is not until you take the rover files back to the office and process them using differential correction software and data from the base station file, that you get corrected positions（.直到你把流动站文件带回办公室并利用差分改正软件和基准站的文件数据进行处理，你才能得到改后位置）The base station file contains information about the timing errors.（基准站文件包括同步误差信息）This information allows the differential correction software to apply error corrections to the roving receiver file during processing（.这种信息可以在处理时使差分改正软件把误差改正施于流动接收机文件上。）Since the base and rover receivers have to “see” the same set of satellites at the same time, the base file has to start before the rover file starts, and end after the rover file ends (a base station is normally set up to track all satellites in view, insuring that it will “ see” at least the four satellites that the roving receiver is using to compute positions)（.由于基准站接收机和流动站接收机必需同时“看到”同一组卫星，基准站文件必需开始于流动站文件之前，结束于流动站文件之后（基准站通常设置为跟踪所有视野内的卫星，以保证至少“看到”流动站接收机用来计算位置的 4 颗卫星））Post-processed differential correction, then, requires both base and rover receivers that are capable of collecting and storing files.（后处理差分改正，要求基准站接收机和流动接收机都能收集和存储文件。）Most recreational grade receivers cannot collect and store files that can be differentially corrected.（多数休闲级接收机不能收集和存储可以用来差分改正的文件）How Accurate Is GPS?（GPS 准确度如何？）The accuracy that can be achieved using GPS depends on the type of equipment used, the time of observation, the positions of the satellites being used to compute positions, the model and the software you used.（使用GPS 可以达到的准确度依赖于使用装置的类型、观测时间、用来计算位置的卫星的位置、你所使用的模式和软件）In general, recreational and mapping grade receivers using C/A code without differential correction are accurate to between 30 and 100 meters.（大体上讲，使用C/A 码没有差分改正的休闲和绘图级接收机精度在30 到100 米之间。）Many people using recreational grade receivers don’ t realize they cannot get highly accurate readings using them autonomously (without differential correction)（.许多用休闲类接收机的人没有意识到他们直接使用（没有差分改正）它们不能取得高精度的读数。）Unfortunately ,some manufacturers’ ads are misleading and only confuse the
situation.（不幸地是，有些厂商的广告误导并混淆了这种情况）They claim 30 meters accuracy, which actually means 30 meters GEP (circular error probable).（他们宣称有30 米的精度，实际上那意味着30 米的GEP（圆概然误差）This means that positions will be within 30 meters 50 percent of the time.（这意味着这个位置有50％的机会在30 米内）There is really no way to tell whether you are within 30 meters or within 100 or more meters of the true position.（实在不能说你是在真实位置的30 米内或者100 米内或着更多米内）
Most mapping and recreational grade receivers with differential correction can provide from about 2 to 5 meters accuracy（.大多数差分改正的测图和休闲类接收机可以提供2到 5 米的准确度）Some receivers use what is called “ carrie r-smoothed code” to increase the accuracy of the C/A code.（有些接收机利用被称为“载波平滑码”来增加C/A 码的精度）This involves measuring the distance from the receiver to the satellites by counting the number of waves that carry the C/A code signal.（这涉及利用计算承载C/A 码信号的载波数来测量从接收机到卫星的距离）These receivers can achieve 10 cm to 1 meter accuracy with differential correction.（这些接收机可以利用差分改正达到10cm 到1 米的精度）Dual frequency survey grade receivers using more advanced network survey techniques can achieve centimeter to millimeter accuracy（.双频测量型接收机利用更先进的联合测量技术，可以达到厘米到毫米的精度）
Unit22 Competition in Space Orbit（太空轨道上的竞争）
Around the world, countries are mobilizing to build independent satellite navigation networks, troubled that the Global Positioning System (GPS) is run by the US military and controlled by the US government.（环绕世界，顾虑到GPS 由美国军方运作并受到美国政府的控制，许多国家都努力建立独立卫星导航网）On March 7, 1995 was announced the Russian Federation Government’s decree “On executing works in use of the GLONASS system for the sake of civil users”（.在1995.3.7，俄罗斯联邦政府宣布一项法令“GLON ASS 系统民用计划”）
It was also reported on “ 21st century” , 2001 that the European Union says the US couldn’ t guarantee the reliability and availability of the GPS civilian signal, as United States national security needs could potentially outweigh any other needs.（2001 年“二十一世纪”也报道说，欧盟说美国不能保证GPS 民码的可靠性和有效性，由于美国国家安全需要潜在地超过了其它任何需要）“Europe cannot accept reliance on a military system which has the possibility of being cut off,” said Rene Oosterlinck, head of the navigation department at the European Space Agency ,fairly summing up the emotions GPS brings about abroad.（“欧洲不能接受依赖一个有可能被切断的军方系统”，Rene Oosterlinck说道，欧洲航空局导航部主任，清楚的概括了GPS 对国外产生的情绪。）
In response, Europe will spend billions assembling a civil satellite system called Galileo ,scheduled to be operation by 2008.（作为反应，欧洲将花费数十亿装配一个民用卫星系统称为“Galileo”，预期在2008 年运转
For the benefit of students to get some knowledge on the competition in space orbit, brief introduction to GLONASS, GALILEO and BEIDOU is provided as follows.（为了使学生们得到一些太空轨道上的竞争的知识，下面提供了关于GLONASS，GALILEO 和北斗的简要介绍）
GLONASS（GLONASS）
The Russian Federation’s GLObal Navigation Satellite System (GLONASS) was developed for the Russian military and was declared operational in 1996.（俄联邦的全球导航卫星系统（GLANASS）是由俄罗斯军方开发的，并在1996 年宣布运行）Fully deployed GLONASS constellation is composed of 24(21 operational + 3 spares) satellites in three orbital planes whose ascending nodes are 120 degrees apart.（全配置的GLONASS 星座由24（21 运行＋3 备用）颗卫星在三个轨道平面中，其升交点相差120 度）8 satellites are equally spaced in each plane with argument of latitude displacement of 45degrees （.8 颗卫星平均分布在升交角距相差45 度的每个平面内）Besides the planes themselves have 15 degrees argument of latitude displacement.（此外轨道平面它们自己有15 度的升交角距差）Each satellite operates in circular 19,100 km orbits at an inclination angle of 64.8 degrees and each satellite completes an orbit in approximately 11 hours 15 minutes.（每个卫星在19100 公里的圆轨道上运转，倾
角为64.8 度，每个卫星完成一次绕轨飞行大约11 小时15 分钟）
The spacing of satellites in orbits is arranged so that minimums of 5 satellites are in view to users worldwide.（轨道卫星间隔被安排能够使使用者最少能看到5 颗卫星）GLONASS constellation allows providing continuous and global navigation coverage for performing of successful navigation observations.（GLONASS 星座能够为成功的航行观测的执行提供持续的和全球的导航覆盖Each satellite transmits radio frequency navigation signal containing navigation message for users.（每个卫星发射包含导航信息的无线电频率导航信号给使用者）
The GLONASS Constellation is operated by Ground-based Control Complex (GCC).（GLONASS 星座由地面控制部分（GCC）来操作）It consists a System Control Center (SCC) and several Command Tracking Stations (CTSs).（它是由一个系统控制中心（SCC）和几个置零跟踪站（Cuts）组成The CTSs track the GLONASS satellites in view and accumulate ranging data and telemetry from the satellites signals.（CTSs 跟踪所见到的GLONASS卫星，并根据卫星信号收集距离修正数据和进行遥测）The information from CTSs is processed at the SCC to determine satellite clock and orbit states and to update the navigation message of each satellite.（CTSs 的信息经SCC 处理，确定卫星时钟和轨道状态，并上传导航信息给每个卫星）This updated information is transmitted to the satellites via the CTSs, which are also used for transmitting of control information.（上传的信息经CTSs 发射，也用来做校准信息的发射之用）Compared with GPS, GLONASS has the following characteristics: （与GPS 相比，GLONASS 有以下特点：）⑴dual-frequency (L1 in the range: 1597-1617 MHz; L2 in the range:1240-1260 MHz);（⑴双频（L1 范围：1597-1617 MHz；L2 范围：1240-1260 MHz）⑵each satellite transmits a different frequency on L1 and L2;（⑵每个卫星以L1 和L2波段发射不同的频率⑶a different datum and time reference system to GPS;（⑶与GPS 有不同的基准和时间参考系）
⑷PPS (Precise Positioning Service) and SPS(Standard Positioning Service) as in the case of GPS;（⑷同GPS 一样，有PPS（精密定位服务）和SPS（标准定位服务））
⑸no Selective Availability is implemented.（⑸没有选择可用性的执行
Although some of the characteristics of GLONASS are very similar to GPS, there are nevertheless significant technical differences, in addition, the level of maturity of the user receiver technology and the institutional capability necessary to support the GLONASS space and control segment are significantly less than in the case of GPS（.虽然GLONASS的某些特性与GPS 非常相似，然而仍有重大的技术差别，另外，客户接收机技术的成熟水平和用来支持GLONASS 空间和控制部分所必需的制度上的性能比GPS有显著的不如）GLONASS will continue to be viewed by many user communities as a technically inferior system to GPS, a system concerning which there are many question marks regarding its long-term viability（.GLONASS 将继续受到许多用户社团的关注，作为比GPS 技术上次等的系统）This uncertainty is stifling much needed market investment in new generation receiver hardware.（这个非常令人郁闷的不可靠的问题需要市场投资新一代接收机硬件）Although GLONASS has the potential to rival GPS in coverage and accuracy, this potential is unlikely to be realized in the medium term, and hence for the foreseeable future GLONASS should be considered a complementary system to GPS. （虽然GLONASS 有潜力在覆盖和精确度上与GPS竞争，这种潜力被认为在中期是不太可能的因此在可预见的将来GLONASS 将被考虑作为GPS 的一个补充系统）The combination of GPS and GLONASS is part of a Global Navigational Satellite System(GNSS).（GPS 和GLONASS 的联合是全球导航卫星系统（GNSS）的一部分）Although there are GLONASS-only receivers available on the market, these are generally inferior to GPS products. （虽然市场上有可用的GLONASS 接收机，一般要差于GPS 产品）However, there is a distinct trend to develop receivers that can track and process signals from both the GPS and GLONASS satellites.（可是，有一种明显的倾向，发展接收机使之可以跟踪和处理来自GPS 和GLONASS 卫星的信号）A combined GPS+GLONASS receiver can track signals from a 48-satellite constellation, twice as many as the GPS-only constellation and therefore significantly improving
availability.（一台组合GPS＋GLONASS 接收机可以跟踪从一个
48 颗卫星星座传来的信号，是GPS 星座的两倍，因此显著地提高了其实用性.。GALILEO（伽利略）
Satellite navigation users in Europe today have no alternative other than to take their positions from US GPS or Russian GLONASS satellites.（现在，欧洲卫星导航的使用者除了使用美国的GPS 或俄罗斯的GLONASS 卫星定位，没有其它选择了。Yet the military operators of both systems give no guarantee to maintain an uninterrupted service.（然而这两个系统的军方操控者都不给出保证维持不间断的服务）As far back as the early 1990s, the European Union saw the need for Europe to have its own global satellite navigation system.（早在90 年代早期，欧盟看到欧洲需要自己的全球卫星导航系统）GALILEO, an independent system under civilian control which will be guaranteed to operate at all times, is a joint initiative of the European Commission (EC) and the European Space Agency (ESA).（GALILEO，一个被控制为民用的独立系统，将可以保证一直运行，由欧共体（EC）和欧洲航天局（ESA）共同发起The mission is now at the point of moving from definition to full-scale development（.从一个概念到全面的发展，这项任务现在接近运行了）⑴the GALILEO infrastructure is being implemented in three phases.（⑴GALILEO 基础设施由3 个阶段实现⑵development and In-Orbit Validation(2002-2005).（⑵开发和轨道内检测（2002－2005）
⑶deployment (2006-2007).（⑶部署阶段（2006－2007））⑷commercial Operations (from 2008).（⑷商业运行（从2008 开始））
The first experimental satellite, part of the so-called GALILEO System Test Bed (GSTB)will be launched in the second semester of 2005.（第一颗实验卫星，号称伽利略系统实验床（GSTB）的一部分，将在2005 下半年发射The objective of this experimental satellite is to characterize the critical technologies, which are already under development under ESA contracts（.这颗实验卫星的目标是定性关键性技术，已经在ESA 合同发展之下了）
Thereafter up to four operational satellites will be launched in the timeframe 2005-2006 to validate the basic GALILEO space and related ground segment.（其后轮到4 颗运作卫星将在2005－2006 时间框架内发射，确认基础的GALILEO 空间和相关地面部分
Once this In-Orbit Validationphase has been completed, the remaining satellites will be installed to reach the full operational capability in 2008（.一旦这个轨道内检测阶段完成，剩下的卫星将在2008 年被安置以达到全运行能力）
The fully deployed GALILEO system consists of 30 satellites (27 operational +3 active spares), positioned in three circular Medium Earth Orbit (MEO) planes in 23616km altitude above the Earth, and at an inclination of the orbital planes of 56 degrees with
reference to the equatorial plane.（全部署的GALILEO 系统包括30 颗卫星（27 颗运行＋3 颗主动式备用），安置在海拔23616 公里的 3 个圆形的中地球轨道（MEO）平面上，在与赤道面成56 度的轨道面的倾角上
Once this is achieved, the GALILEO navigation signals will provide a good coverage even at latitudes up to 75 degrees north, which corresponds to the North Cape, and beyond.（一旦这种情况达到，GALILEO 导航信号将提供良好的覆盖—甚至在75 度纬度以北，相当于North Cape，甚至更北）
The large number of satellites together with the optimization of the constellation, and the availability of the three active spare satellites, will ensure that the loss of one satellite has no discernible effect on the user.（大量的卫星连同星座的最优化，和三颗主动式备用卫星的有效性，将保证一颗卫星的损失不会被使用者产生多大的影响）
Two GALILEO Control Centers will be implemented on European ground to provide for the control of the satellites and to perform the navigation mission management.（两个GALILEO 控制中心将在欧洲地区建立，提供对卫星的控制和执行导航任务管理）The data provided by a global network of twenty GALILEO Sensor Stations will be sent to the GALILEO Control Centers through a redundant communications network.（由二十个GALILEO 监测站组成的全球网提供的数据将发送至GALILEO 控制中心通过一个备用的通讯网络）The GCCs will use the data of the Sensor Stations to compute the integrity information and to synchronize the time signal of all satellites and of the ground station clocks.（GCCs
将使用检测站的数据计算完整性信息，并同步所有卫星和地面站时钟的时间信号）The exchange of the data between the Control Centers and the satellites will be performed through so-called up-link stations.
（在控制中心和卫星之间的数据交换将通过所谓的卫星上行链路站执行）Five S-band up-link stations and 10 C -band up-link stations will be installed around the globe for this purpose.（为了这个目的，五个S 波段上行链路站和10 个C 波段上行链路站将在全球范围内安置）
Unlike GPS and GLONASS, which was essentially designed for military use, GALILEO has been designed and developed as a non-military application, while nonetheless incorporating all the necessary protective security features.（不同于GPS 和GLONASS，其本质上设计用于军事用途，GALILEO 作为一个非军事应用，来设计和发展的，虽然如此，它还是整合了所有必要的防护性安全的特点）It is based on the same technology as GPS and provides a similar and possibly higher degree of precision.（它是基于和GPS 相同的技术，提供一个类似或者更高的精度。）By placing satellites in orbits at a greater inclination to the equatorial plane than GPS, GALILEO will achieve better coverage at high latitudes.（由于比起GPS，其卫星放置相对赤道面轨道有一个更大的倾角，GALILEO 将在高纬度获得更好的覆盖）This will make it particularly suitable for operation over northern Europe, an area not well covered by GPS.（这将使得它特别适合北欧地区使用，该地区GPS 覆盖率不很好）
GPS,GLONASS and GALILEO, the three systems will be fully interoperable, which means that a user on Earth will be able to determine a position with any receiver picking up signals from any combination of satellites belonging to any of the three systems.
（GPS,GLONASS 和GALILEO，这三个系统将能够完全的共同使用，这意味着一个地球上的使用者将可以使用任一接收机从属于任一三个系统的任一卫星组接收信号确定一个位置）
BEIDOU（北斗）
BEIDOU is a satellite positioning and navigating system developed and deployed independently by China.（北斗是一个由中国独立发展和部署的卫星定位和导航系统）The space segment of this system consists of 3 (2 operational +1 spare) geo-synchronous satellites orbiting 360,000km high above the Earth.（这个系统的太空部分由 3 颗（2 颗运行＋1 颗备用）地球同步卫星运行于距地球360000 公里的轨道上）The two operational satellites were both launched in 2000 and they have operated stably since then.（两颗工作卫星都在2000 发射，它们从那时起一直运行稳定）The spare one was successfully launched on May 25, 2003.（备用的一个在2003 年3 月25 日被成功发射）Although developed for defense purpose, the system will also be applied in civilian uses and will afford considerable advantages in many sectors of the economy of our country.（尽管为国防目的而发展，这套系统也用于民用，将在我国许多经济部门提供相当可观的利益）Compared with Global Navigation Satellite Systems (GPS, GLONASS and GALILEO),BEIDOU should in fact be called a Local Navigation Satellite System.（与全球导航卫星系统（GPS,GLONASS 和GALILEO）相比，北斗实际应该被叫做区域导航卫星系统）It covers the territory and territory sea of China and around ---- longitude 70~140 east, latitude 5~55 north.（它覆盖了中国的领土和领海以及周边地区——东经70－140，北纬 5 －55）
The positioning principles of BEIDOU and GNSS are different.（北斗与GNSS的定位原理不同）GPS, GLONASS and GALILEO are all passive positioning systems that do not require the transmission of signals from users to satellites.（GPS，GLONASS 和GALILEO 都是被动式定位系统，不需要从使用者向卫星发送信号）But BEIDOU is an active positioning system.（但是北斗是一个主动式定位系统）To make use of this system for positioning or navigating, users need to transmit signals to the satellites at first and then signals are re-transmitted to the Ground Control Center.（用这套系统来定位和导航，使用者需要首先向卫星发射信号，然后信号被转送至地面控制中心）GCC computes out the users’ position based on the signals transmitted from the satellites.（GCC 以从卫星传来的信号为基础，计算出使用者的位置）At last, the users get their position information via the satellites.（最后，经由卫星使用者得到它们的信息）Observation data acquisition and position computation are both carried out by GCC（.观测数据获取和定位计算都是由GCC 来实现So it is required that both satellites and receivers own the functions of receiving and
sending or re-transmitting the signals.（因此，这就需要卫星和接收机都有接收和发射或转发信号的功能）
Unit 23 GIS Basics（GIS 的基础）
Definitions of GIS
“GIS”is an acronym meaning of Geographic Information System. In order to provide a good understanding of GIS, the following two definitions given by Rhind (1989) and the United States Geological Survey ( USGS , 1997 ) respectively are presented first
地理信息系统” 是一个缩写含义，地理信息系统。为了提供一个很好的了解，下面给出的定义由兰德（1989）和美国地质调查局（美国地质勘探局，1997）分别是第一次提出.1 “. . . . a system of hardware, software, and procedures designed to support the capture, management, manipulation, analysis, modeling, and display of spatially referenced data for solving complex planning and management problems .”
1“GIS 是一个由硬件，软件，和程序设计，支持捕获，管理，处理，分析，建模，并显示空间参照的数据，以解决复杂的规划和管理的问题的一个系统。”
2 “ . . . . a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information , i . e ., data identified according to their location .”2“。是一个计算机系统能组装
存储操作和显示地理参考信等,根据其位置来数据证实。”
GIS books generally adopt the ideas expressed by these two definitions. These two characteristics distinguish GIS from other types of information systems:
GIS书籍通常采用这两个定义所表达的思想。这两个特征用以区分GIS与其他类型的信息系统:The word “ Geographic ” in GIS explains “spatially” where things are such as the location of nations, states, counties, cities, schools, roads, rivers, lakes, and the list can go on and on . “地理”在GIS的解释是事物所在的“空间” ，比如国家,州,县、市、学校、道路、河流、湖泊等等之类的位置。
Spatiall y means where on the earth’s surface an object or feature is located. This can be as simple as the latitude and longitude of a feature. The geographic feature or object can be anything of interest “Information” in GIS is the“data”or“attribute”information a bout specific features that we are interested in . 空间意味着在地球表面上的一个对象或特征所在地。这可以被简单的理解为一个特征的纬度和经度。地理特征或对象可以是任何我们感兴趣的事物。“信息”在GIS里是指我们感兴趣的空间特征的“数据”或“属性”信息。
The name of the feature, what the feature is, the location of the feature , and any other information that is important . An example could be the name of a city , where it is located , ho w big it is in square feet (area) , its population , its population in the past, and any other information that is important .
特性的这个名字,什么是特性, 特征的位置及关于它的任何其它的重要信息一个范例可以是一个城市的名字,它的位置,它有多大的平方英尺(区域),它的人口,其在过去的人口,和其他重要的信息。
”System “in GIS is the computer software that is written to help people analyze the data, look at the data and combine it in various ways to show relationships or to create geographic models. A GIS can be made up of a variety of software and hardware tools, as long as they are integrated to provide a functional geographic data processing tool .
“系统”在GIS中是指所编写的计算机软件，它用来帮助人们分析数据,查找数据,并以不同方式把它们结合在以一起来显示它们的关系或创建地理模型。GIS系统由各种各样的软件和硬件工具组成,只要它们是集成在一起，就能够提供一个实用的地理数据处理工具。
As mentioned above, GIS is a computer system that links geographic information (where things are) with descriptive information ( what th ings are) . Unlike a flat paper map, where “what you see is what you get” , a GIS can present many layers of different information.
正如上面提到的,GIS 是一个将地理信息（在哪里）和描述性信息（是什么）链接在一起的电脑系统。不像平面纸质地图,“你看到的就是你得到的全部”,一个GIS 可以表达许多层的不同信息。To use a paper map , all you do is unfold it . Spread out before you is a representation of cities and roads, mountains and rivers, railroads, and political boundaries. The cities are represented by little dots or circles, the roads by black lines, the mountain peaks by tiny triangles, and the lakes by small blue areas similar to the real lakes.
使用纸制地图,你所要做的就是打开它。面前展现出你是一个关于城市、道路、山川和河流、铁路、和政治边界的描述。城市用小点或圆表示,道路被黑色线条,山峰通过小的三角形,湖泊由类似于真正的湖泊的小型蓝色区域表示。
A digital map is not much more difficult to use than a paper map. As on the paper map, there are dots or points that represent features on the map such as cities, lines that represent features such as roads, and small areas that represent features such as lakes .
相比纸制地图,数字地图使用没有太大的困难。在纸质的地图上,采用点代表城市类的特地物,采用线代表道路类的线状地物,采用小区域代表河流类的特征地物。
All this information— where the point is located , how long the road is, and even how many square miles a lake occupies—is stored as layers in digital format as a pattern of ones and zeros in a computer . Think of this geographic data as layers of information underneath the computer screen. Each layer represents a particular theme or feature of the map .
所有这些信息——这一点的所在的位置,路是多长,甚至是一个湖占据有多少平方英里都是以数字格式作为图层以 1 或0 的模式存储在计算机里。考虑这个地理数据作为层信息显示在电脑屏幕上。每一层代表地图的一个特定的主题或者特征。
One theme could be made up of all the roads in an area. Another theme could represent all the lakes in the same area. Yet another could represent all the cities. These themes can be laid on top of one another, creating a stack of information about the same geographic area. Each layer can be turned off and on, as if you were peeling a layer off the stack or placing it back on. You control the amount of information about an area that you want to see, at any time, on any specific map .
一个主题可以是由在一个区域的所有道路组成。另一个主题可以表示同一区域内所有的湖泊然而,另一个能代表所有的城市。这些主题可以被放置在另一个之上,创建同一地理区域内的一叠信息.每一层都可以关闭和开启,仿佛你从一叠里剥去一层或把它重新打开。你控制一个区域里的所有信息,你可以在任何时间，任何专题图上浏览它们。
The technology components of a GIS can be explained in terms of hardware, software and human resources. GIS hardware includes: computers, computer configuration/ net works, input devices, printers, and storage systems. GIS 的技术组件在硬件、软件和人力资源这些术语里给予解释。GIS 硬件包括:电脑、电脑配置/网络工程、输入设备,打印机,和存储系统。
Computers for GIS usage can be PCs or supercomputers. These computers can be stand-alone units or can be hooked into a network environment. Input devices include digitizers and scanners. Printers and plotters are used to produce a hardcopy map . GIS storage systems include: optical disks, magnetic disks (such as a hard drive) , floppy disks or magnetic tapes .
用于GIS 的计算机可以是个人计算机或超级计算机这些计算机可以是独立的单元或可以连接到一个网络环境输入设备包括数字转换器和扫描仪打印机和绘图仪是用来产生硬拷贝地图GIS 存储系统包括:光学磁盘,磁磁盘(如硬盘驱动器),软盘或磁带。
GIS software includes both GIS program and special application packages, such as digital terrain modeling and network analysis. The main difference between GIS software programs and desktop mapping programs is the ability of GIS programs to perform spatial analysis. ARC/ INFO by Environmental Systems Research Institute (ESRI) Inc is one of typical examples of GIS software packages.
GIS 软件包括GIS 项目和特殊应用程序包，如数字地面模型和网络分析。GIS 软件项目和桌面制图程序最主要的区别在于GIS 具有空间分析的能力。由美国环境系统研究所(ESRI)有限公司出的ARC/INFO，就是一个典型的GIS 软件包。
Desktop mapping programs offer many of the same features, as a GIS , but their ability to support spatial analyses are limited . They are developed to satisfy individual user needs for mapping presentations. MapInfo developed by MapInfo Corp is an example of popular desktop mapping programs.
桌面制图程序提供许多类似的特性,但作为GIS,它们支持进行空间分的能力是有限的。他们正在开发以满足个人用户需要的地图显示。MapInfo 公司开发的MapInfo 就是一个目前应用较多的桌面制图程序。Human resources used to operate a GIS typically include: operational staff, technical professional staff, and management personnel.
用来操作GIS 系统的人力资源通常包括:操作人员、专业技术人员和管理人员。
Operational staff are people such as( 1 ) cartographers ,who monitor the design of map displays, the
standards for map symbols and standard map series, (2 ) data capturers, who converts map into digital for m and (3 ) potential users of a GIS .操作人员是这样的人:(1)监控设计的地图显示,标准地图符号和标准地图集的绘制(2)将地图转成数字形式的数据获取人员(3)潜在的GIS 系统的用户。Technical professional staff include ( 1 ) information analysts who solve particular user problems and satisfy their information needs, (2 ) system administrators , who are responsible for keeping the system ( hardware/ software) operational, (3 ) programmers , who translate the application specifications prepared by the analyst into programs and ( 4 ) the database administrator , who assists the analysts, programmers and users to organize geographic features into layers, identify sources of data , develop coding structures for non-graphics data, and document information about the contents of the databases .
专业技术人员,包括(1)解决特定用户的问题并满足他们的信息需求的信息分析员,(2)负责保持系统(硬件/软件)运行的系统管理员(3)将分析师准备好的应用程序规范编译成项目的程序员,和(4)协助分析员,程序员和用户将地理特征组织到每一层,确定的数据来源,为非图像数据开发编码结构和管理数据库的文档信息的数据库管理员。Management personnel include (1) the manager, who monitors the daily performance of the GIS project implementation team and manages the output production as required by the organization and (2) the Quality Assurance Coordinator who manages the output of the final product to ensure that it meets the conversion specification and data acceptance plan.
管理人员包括(1)经理, 监控GIS 项目实现团队的日程的和管理按组织的要求生产输出(2)质量保证协调员负责最终产品的输出,以确保它满足了转换规范和数据验收计划。
How a GIS Works:
A GIS works by providing a way to capture or input data , store , retrieve and manage the data , manipulate and analyze the data , and finally a way of di splaying that data as a map or as a document or both . Let’s take a closer look as each of these aspects of GIS .
GIS 是通过提供一种方式来捕获或输入、存储、检索和管理数据、处理和分析数据, 最后以一种方式将数据显示为一个地图或一个文档或两者。让我们来仔细看一下GIS 的每个方面。Data Input: All GIS data has to be in a digital format so whether it ’s a report, a photo , a map , or information gathered in the field , it has to be made digital . Obtaining geographic data to insert into a GIS is a large subject in which includes a number of different approaches.
数据输入:所有GIS 数据必须是数字格式，因此无论是报告、照片、地图,或者收集到的一个区域的信息,它必须是数字。将获取的地理数据输入一个GIS 是一个包括许多不同的方法的大型工程。One of the most common ways to collect spatial geographic data is to performa physical survey. This includes surveying the land, underwater areas, and underground features of the earth (which are referred to as field survey,hydrographic survey and mining survey respectively).
空间地理数据收集的最普遍的方法之一是的进行一项物理测量。这包括测量土地,水下地区,和地球的地下特性(这分别被称为野外测量、水文测量和矿山调查)。Basic forms of data input include: ( 1 ) Typing:Reports, survey documents, population statistics , etc ., all have to be entered into the computer preferably in a data base format or as tabular data .( 2) Scanning: Paper maps such as topographic maps, aerial photographs ,remotely sensed images if not already in a digital for m at need to be scanned and then georeferenced or georectified . When a picture or a map or an aerial photo is georeferenced it will open in a GIS program in the right place on a map in relation to other map objects being viewed . They will be in the proper place spatially .
基本形式的数据输入包括:(1)打字:报告测量文件,人口统计数据等等所有这些最好以一个数据基础格式或表格数据输入电脑。(2)扫描:纸质地图如地形图,航拍照片,遥感图像如果不是数字格式，则需要扫描,然后匹配或矫正地图。当一幅图片或一个地图或航拍照片是匹配过的，它会以正确的位置被GIS 打开在一个地图上,与其它相关的地图对象一同被显示。他们将在空间上的正确位置。
(3) Digitizing: Currently digitizing is the most common method for converting existing maps and images into digital form. Digitizing is basically tracing points, lines, or areas from a paper map, or aerial photo so that instead of a photograph or a raster image , is now a digital line graphic or vector file .
(3)数字化:目前数字化是最常见的将现有的地图和图像转换成数字形式的方法。数字化基本上是从纸质地图或航空相片跟踪点、线或区域来替代一个照片或一个栅格图像, 变成一个数字图形或矢量文件。
(4) GPS data capture: Data can also be placed in a GIS as points, lines, and polygons from a GPS unit if it has the capability of recording such information. (5) Aerial photography/remote sensing: This is an increasingly popular way to gather spatial data. Aerial photographs are taken from an aircraft, after which they are measured and interpreted. Similarly, satellite remote sensing can be interpreted for physical features and attributes.
(4)GPS 数据捕获:数据可以作为为点、线和多边形从GPS 装置放置到一个GIS 里，如果GPS 具有记录这种信息的能力。(5)航空摄影/遥感:这是一种越来越流行的方法来收集空间数据。摄影测量采取一架飞机,这从而数据被测量和解释。同样,卫星遥感技术可以被解释为物理特性和属性。
(6)Censuses: Censuses conducted by the U .S. Census Bureau gather a variety of demographic data such as population, age structure, sex ratio, race composition, employment rates . (7)Statistics: Statistics are a set of mathematical methods used to collect and analyze data .These methods include the collection and study of data at different time intervals and at a fixed location, providing information for yearbooks, weather station reports, etc .
(6)的人口普查:人口普查由美国人口普查局管理，它们收集各种的人口数据诸如人口、年龄结构、性别比例、种族组成,就业率。(7)统计:统计数据是一组用于收集和分析数据的数学方法。这些方法包括在一个固定地点的不同的时间间隔收集和研究数据,为年鉴、气象站报告等提供信息。这此信息通常有一个空间结构，因此，可以被合并到GIS 中。（8）追踪：追踪是收集发生在一个位置上的在一段时间内正在变化的数据的过程。测绘的例子包括：监测一个变化的生态系统，实时监测一个变化的目标比如车辆。
数据存储、检索和管理：不同类型的信息被获取到GIS 存储系统，这个系统可以使信息被更新和询问，以便于用户分析。有两种信息类型会被存储，空间数据和属性数据，这将会在下一篇文章中讨论。
数据管理和分析：一个好的系统或软件包允许用户定义和操作空间和属性过程。这通常被我们理解为GIS 的核心。覆盖、缓冲、建模和分析是一些用于建立一个范围或工程的方法。它也使得用户具备知识来认识他们在最终的地图和数据里所看到的内容。GIS 的力量来源于数据分析。
数据输出：这通常是指用户在数据分析后形成的一个地图或图像。学校区域可以利用GIS 系统帮助他们确定学校边界并创建一个地图来区分它和社区。成表格数据和报告能够形成并解释地图或图像的细部信息和衍生出来的结论。
Unit24 GIS 中的数据类型和模型
数据类型：GIS 中的数据可以分为三种基本类型:空间数据，属性数据（表）和影像数据.
空间数据---地图的组成
空间数据一般可以存储为专题, 图层，覆盖。有地理坐标的空间数据在GIS 中显示在合适的位置，这些位置和其他空间位置相关，并由附加在空间数据中的地理信息确定。举个例子，Bonnerville Elementary school 的经纬度为42.52.14N ，112，26，28.这个学校的经纬度隐藏在文件中，因此可以根据在城市中的相对位置显示在合适的位置。专题数据可以是当期传统纸质地图上所有，包括道路，河流，城市，井，森林边界，学校区域边界等，并且他们也带有地理坐标。真实世界中的空间数据或空间物体可以归结为出现的四种类型：点数据，先数据，面数据和表面数据。相应的，他们能代表我们日常中的大部分可以接触到的自然和人文现象。一般来讲，点、线和面数据用来解释现实世界中的物体，而表面数据最常用来表示量算体积的物体，如表示山体，峡谷。因此所有的数据可以认为是有明确空间意义的。点特征是指发生在空间中的一个位置的空间现象，每一个点特征作为离散的现象，因为其仅占用空间中的一个点位置，并且可以认为他没有度量特征—没有宽度和长度。这类特征的例子如房子后村庄。但是一个村庄可以用点数据和面数据来表示，这主要取决于数据的精度。线特征定义为在坐标系中占据一个空间度量的特征。他们可以表示为连接的一系列点。道路、河流，都是线状特征的例子。给定数据的精度或尺度也给定了限度，可以把它们想象为没有宽度的特征。线数据不像点数据，允许我们量测他的长度。面特征是含有长度和宽度两个度量的特征。面是由在同一位置首尾相连的一系列线组成的。我们可以描述他的形状、方向和占用区域的面积。在数据库中，专有名词多边形经常用来替代面。和尺度相关的物理尺寸可以决定
一个物体表示为面或点。
通常情况下面可以分割为正方形或举行，因此所有的物体都可以从面的角度进行描述。这种数据结构可以成为格网，每一个正方形或矩形作为一个单元和代表一个统一的值。给面特征添加高程高度度量则可以让我们观测和记录存在的表面。表面有三个特征---长度、宽度和高程。例如，山体、峡谷和山脊可以标明他们的位置，所占面积，他们的方向，记录他们的高程进行描述。属性/表数据----地图中添加到信息属性数据是物体或特征的信息。例如我们的学校，学校的名字、位置、学校的行政区域、每年的入学人数等。属性数据通常保存在数据库、表或电子表格类的格式中。表数据是描述地图特征的信息。例如，一张地图的顾客位置信息可以和这些顾客的统计信息连接。GIS 中所用的表数据，我们可以直接购买表数据和空间数据连接好的数据，也可以按照我们自己的方式进行组织。如果你有顾客名单，电子表格数据，或含有顾客名单，办公室地点，和其他信息的数据库，你就可以在GIS 中使用这些信息。如果你有正确的空间数据，GIS 可以把你的表数据和空间数据进行连接。例如，你可以在地图上创建办公地点的点，或者你可以将促销信息和邮政区划信息连接，这样就让你可以根据邮政区划对促销信息进行规划（计划）；你已有的表数据可以用来和购买信息的表数据组合，这样可以帮助你更好的分析数据。也许你想要把你邮政编码区划的销量、可用的商业数据，例如根据邮政编码的统计数据进行连接，绘制一个邮政区划社区的统计图。时间也可以当作一个数据元素，因为地理坐标信息经常随时间变化。例如，一个河流的路线随时间变化，或者河流的分支可能因为经历洪水而变化，一些野生生命的生活特征变化，土地利用随着农业和工业利用的变化。影像数据-----利用影像数据创建地图影像数据包括多种组成如卫星数据、航空数据和扫描数据------从纸质格式转化为电子格式。相比每次获取像建筑物、道路、湖泊等图层的方式，影像数据提供一种快速、廉价而有效的获取大区域范围空间数据的方式。但是影像文件是一个文件或图层，因此你不能把它分解为不同的成分且分别给其附加数据。如果你只想向一个矢量数据中添加没有附加信息的点数据，影像数据是最好的选择。影像可以与其他含有地图属性的空间数据一起进行显示，它也可以是地图属性的特征。也就是说，你可以把影像添加到其他地图特征之中，只要你点击那个特征就会显示你添加到影像。例如，你有一张加利福尼亚州的城镇图，通过点击上面San Francisco 那个点，你就可以打开San Francisco 的影像。数据模型
另外，GIS 数据可以更深层次的分为两类数据模型：矢量数据模型和栅格数据模型。矢量数据模型离散特征，例如顾客的位置和区域的概括数据，一般用适量数据进行表示。矢量数据把每一个特征表示为表中的一行，并且属性的形状有空间的xy 坐标表示（GIS 根据点绘制线和轮廓）。特征可以是离散的位置、时间、线或区域。位置，例如一个顾客的地址，或者犯罪的现场等被表示为含有一对地理坐标的点。线，例如溪流或道路，被表示为一系列的地理坐标点对。面定义为边界，被表示为封闭的多边形。他们可以被合法的定义，例如一块地；行政区划，如国家；或者自然边界，如分水岭。当你分析矢量数据，你的大部分分析包括概括图层表中的属性数据。栅格数据模型连续的数字特征，例如高程，和连续的类别，例如植被类型，经常用栅格数据进行表示。栅格数据模型用空间连续的矩阵单元表示特征。一个点就是一个单元，一条线是一行单元，一个面表示连续的接近的单元。每一个层表示一个特征（尽管其他特征可以归属为一个单元）。大部分的分析工作会产生在把不同的层进行叠加产生新的矩阵单元的图层。单元（像元）的尺寸会影响到分析的结果和地图的呈现。像元的大小应该基于原始地图的比例尺，最小的成图单位。使用过大的像元尺寸会遭成信息的损失，使用过小的像元尺寸会造成存储空间的浪费，没有增加地图的精度却加大处理时间。而哪种特征用什么模型进行表示，离散特征，如顾客的位置、电线杆的位置或其他，区域的统计数据如邮政区号区域，湖泊等，通常用矢量数据模型进行表示。连续的类别，如土壤的类型，降雨量、或高程等，可以用栅格也可以用矢量数据模型表示。
Unit25 Digital Terrain Modeling（数字地面模型）
The creation of digital models of the terrain is a relatively recent development, and the introduction of the term Digital Terrain Model (DTM) is generally accredited to two American engineers, Miller C. and LaFlamme R.A., working at the Massachusetts Institute of Technology during the late 1950s(Petrie and Kennie, 1990) . The definition given by the m is as follows:数字地面模型的创建在近期才得到了较好的发展，50 年代后期，DTM 这个术语被工作在马萨诸赛州科技学会的美国的两位工程师XX 和XX
所认可，他们给出的定义如下：
“A statistical representation of the continuous surface of the ground by a large number of selected points with known X, Y and Z coordinates in an arbitrary coordinate field.”
利用一个任意坐标系中大量选择的已知X、Y、Z 的坐标点对连续地面的一个简单的统计表示。Digital Terrain Modeling is the electronic process of representing topography in three dimensions. It consists of a number of surface points that are representative of the terrain and designate the positions of points in relation to a common reference frame. In common usage, the X and Y coordinate fix the horizontal position of the point, and Z refers to the elevation.
数据地面模型是采用三个量来代表地形的电子过程。它包括大量的代表地形的地面点并指定这些点在一个相关的通过参考框架中的位置。在常规的应用中，X 和Y 坐标确定点的水平方向，Z 坐标是指点的高程。
A DTM may involve a range of geographical elements and natural features such as rivers or ridge lines and may include derived data about the terrain such as slope, aspect, visibility,etc.一个DTM 可能包括许多的像河流、山脊线一样的地形要素和地表特征，还可能包括地形的原始数据，如坡度、坡向、能见度等。The term Digital Elevation Model (DEM) specifically relates to the height above a datum and theabsolute elevation of the points contained in the model. In any case, the term usually refers to the creation of a regular array of elevations, normally in a square grid, over the terrain.数据地面模型这个术语具体地与相对于一个基准的高度有关并且这个模型里面包括这些点的完整的高程。因此，这个术语经常指在一个地形上创建一个高程的规则排列，经常是以一个正方形格网的形式。The manipulation of the data in such a form in a computer system is straightforward since a DEM is essentially a two dimensional matrix.
在计算机里以这种方式管理数据因为DEM 本质上是一个二维的矩阵。DTM is a multistep process that is made up of the following sequence of tasks[C.P.Loand Albert K .W.Yeung,2002 ] :制作DTM 的多级过程根据以下一系列步骤：
Digital terrain data sampling is the structuring and acquisitions of digital terrain data by photogram metric, cartographic, and field survey methods. 数字地形数据采样是采用摄影测量、制图和野外测量方法构建和获取数据地形数据；
(2)Digital terrain data processing is the manipulation of digital terrain to ensure their usability by GIS.数字地形数据处理是管理数据地形以确保它们在GIS 中的应用。(3)Digital terrain data analysis involves the use of algorithms and procedures that restructure digital terrain data into useful geographic information.数字地形数据分析包括则将数字地形数据重构成有用的地形信息的算法和过程。(4)Digital terrain data visualization entails the development of algorithms and methods that allow the effective display of the terrain to assist in spatial problem solving and decision making.
数字地形数据的可视化使地形的有效显示来帮助解决问题和制定决策的算法和方法的发展成为一种必要。(5)Digital terrain data applications comprise the practical use of DTM in different fields of science and technology.
数字地形数据应用包括DTM 在不同科技领域的实际应用。
Digital TerrainData Sampling（数字地面数据采样）
There are two approaches to digital terrain data sampling: systematic and adaptive. In systematic terrain data sampling, elevation points are measured at regularly spaced intervals (Regular Grid).The result is a matrix of elevation values that is usually referred to as a digital elevation model (DEM).
数字地形数据的采样有两种方法：系统方法和自适应方法。在系统地形数据采样中，高程点在等间隔的空间位置被测量（规则格网）。结果是一个关于高程值的矩阵，这个矩阵通常被称为数据高程模型（DEM）。
The locations of elevation points in DEM are implicit in the data model. When adaptive sampling method is used, elevation measurements are made at selected points that are assumed to be representative of the terrain.
在这个模型中，DEM 上高程点的位置是明确的。当采用自适应的方法进行采样时，采用选定的点进行高程的测量，以此来假想代表地形。The result is a collection of irregularly distributed elevation values that must be properly structured before they can be used for further processing. Since the method of
triangulation is used to build the spatial framework for storing the elevation values, the data collected by this approach are referred to as a triangular irregular network (TIN).这个结果是一个不规则高程值划分的集合，它在应用于进一步的处理之前必须经过合理地构建。由于三角测量方法被用于建立空间框架来存储高程数据，采用这种方法所收集到的数据被称为不规则三角网。TIN is a model of the vertices of triangles generating from the distributed data set, which form uniquely spaced nodes. Unlike the grid (regularly spaced intervals), the TIN provides for dense information in complex areas and sparse information in homogeneous areas. The TIN data sets provide topographical value among points and their neighboring triangles.
TIN 是由数据集产生的三角形顶点的模型，该数据集形成独特的间距节点。不像格网（规则的空间间隔），TIN 提供的信息，复杂地区信息量大，平坦地区信息量小。Tin 可以提供网点中高程值及其相邻三角形的信息。The TIN data model is distinct from the DEM data model in two important ways: each and every sample point in a TIN has an (X, Y) coordinate and an elevation, or Z value; the TIN data model may include explicit topological relationship between points and their proximal triangles.
TIN 数据模型和DEM 模型的两个主要区别：TIN 中的每一个点都有X,Y 坐标和高程或Z 值；TIN数据模型可以包含点和临近多边形的拓扑关系。Digital terrain data may be acquired by a variety of methods, depending on factors such as the location and size of the area of interest, the purpose of the terrain modeling, and the technical resources available. Generally speaking, ground survey methods are most suitable for large scale terrain modeling for engineering and mining applications.数字地面模型数据可以通过多种方法获取，主要依据例如兴趣区域的位置和大小、地面模型的目的及可用的仪器。一般来说，以工程和采矿应用的大尺度地形建模中，地面测量方法是最合适的一种方法。At smaller scales covering larger geographic areas, photogram metric methods are always used. Currently terrain information may be acquired by remote sensors on airborne platforms. However, as a vast amount of terrain data are already in existence in topographic maps, many national mapping agencies tend to acquire digital terrain data by digitizing existing maps. Digital terrain data sets obtained in this way are usually of a small scale and have a national or regional coverage.
对于较小尺度覆盖的较大地形区域，摄影测量的方法则经常使用。当前地形信息可以通过装载在航空平台的遥感传感器来获取。另外，由于在现存的地形图中已经包含了大量的地形数据，很多国家的制图机构常通过数字化已有的地图获取数字地面模型。以这种方法获取的数字地面模型集合通常是小尺度的，并且覆盖整个区域或国家的。
Data Processing and Analysis（数据处理和分析）
The core activities of digital terrain modeling involve three typical phases: processing terrain data to ensure that they are optimized for storage and application; performing analysis to convert topographic attributes (elevation, slope, aspect, profiles curvature, and catchments (area) derived from DEM s or TINs into useful terrain information; and presenting the terrain information to the user in an easily understandable manner. Mesh simplification is the process by which a TIN model is constructed from DEM data.
数字地形建模的主要工作涉及三个方面：处理数据以确保数据可以最有效的存储和应用；使从DEM 或TIN 中衍生的地形要素（高程、坡度、坡向、剖面图，流域）转化为有用的地形信息；把地形信息用简单易懂的方式呈现给使用者。网格简化指将DEM 数据生成TIN 模型。The objective is to extract from a DEM the topographically important elevation points to form a TIN with the minimum number of points possible, while at the same time preserving the maximum amount of information about terrain structure. This is an essential function in digital terrain data processing because it allows the user to take advantage of both the DEM and TIN models.其目的是从DEM 中提取重要的地形高程点，用尽可能少的点形成TIN，而同时最大限度的保留地
形信息。这是数字地形数据处理的最重要的功能，因为它可以让使用者更好的利用DEM 和TIN 的优点。
The DEM approach is more suitable than the TIN approach for automatic digital terrain data sampling. With mesh simplification techniques and powerful computers, it is now possible to acquire digital terrain data with DEM approach. The data are then processed to form TINs to optimize storage and modeling efficiency.在自动化的地形数据采样中，DEM 的方法比TIN 的方法更加使用。利用网格简化技术
和强大的计算机，现在可以通过DEM 的方法获取地面的地形数据。然后将得到的数据处理构成TIN 以节约存储空间和提高建模效率。
Interpolation is the process by which elevation values of one or more points in geographic space are used to produce estimated values for positions w here elevation information is required. It is used for contouring and for the generation of DEMs from selectively or randomly sampled elevation points.
内插是利用空间区域中一个或多个点的高程估计产生指定位置的高程信息，经常被用来从离散的或选取的高程采样点中产生等高线和DEM。
A surface-fitting algorithm is commonly used to improve the result of terrain modeling. It may be linear or nonlinear, depending on the order of the polynomial equations used for estimating the elevation of the required point.曲面拟合算法通常被用来提高数据建模的结果。它可以是线性的或非线性，主要取决于估算指定点高程的多元方程的阶数。
Digital TerrainVisualization（数字地形的可视化）
The ultimate aim of D T M is to present relevant terrain information about a given geographic space that results from the analysis of the characteristics of its topography and related spatial phenomena. Visualization is therefore an integral component of DTM, forms the perspective of both process and technology.
数字地面模型的最终目的是展示关于给定区域的地形信息，此区域是从对DTM 地形信息的分析和相关空间现象中得到的。因此可视化是DTM 的组成部分，组成了过程和技术透视图？
There are numerous well developed techniques for digital terrain visualization. According to the dimension of the graphical display, digital terrain visualization can be classified as: two dimensional, two and a half dimensional, three-dimensional, and multidimensional. Contour lines are the most conventional and probably still the most commonly used method of digital terrain visualization.
已经有大量精心设计的数字地面模型可视化方法，根据图形显示的维数，数字地形可视化可以分为：二维的、2.5 纬的，三维的和多纬的。
Using contour line is a quantitative way of representing three-dimensional terrain in two dimensions because numerical measurements of elevation may be readily made on the display. A two-and-a-half dimensional display is basically an isometric model.
等高线是最常用的，并且是最广泛的一种数字地形可视化方法。使用等高线是一种用二维地形表达三维地形的定量化方法，因为高程可以很容易的通过屏幕进行数字量测。In such a model, the Z attribute associated with an X, Y location is projected onto an X, Y, Z coordinates reference system. This transformation the map of Z attributes for an X, Y position so that each Z attribute defines a position on the Z axis, creating a surface that is perceived as three dimensional. A three-dimensional terrain model is a solid model in which many X, Y, Z data points are used to form a solid structure that may be visualized in a perspective view.
2.5 纬的显示从根本上讲是一种等距模型，在这种模型中，和X,Y 位置相关的Z 属性被投影到了X,Y,X坐标参考系统中。三维的地形模型是一个实体模型，该实体模型中，许多的XYZ 数据用来组成实体的结构，并且可以在透视图中进行显示，Unlike a two-and-a-half-dimensional view, which presents only a pseudo perspective of the terrain, a three-dimensional terrain model is an analog for the physical space in nature as perceived by an observer. Three-dimensional terrain-modeling allows the full specification of three-dimensional operations on the objects and phenomena within the constraints of the geo metrical model used.It represents one of the most exciting developments in GIS technology.
和仅显示伪地面透视图的 2.5 纬模型不同，三维地形模型是实际空间中观测者观察到的相似体。三维地形建模允许在所使用的几何模型约束内对物体和现象进行规格齐全的三维操作，它代表了GIS 技术中最令人兴奋的的发展。
Application of DTM（数字地面模型的应用）
Once a DTM has been created, contours, profiles, volumes between surfaces and three-dimensional displays are available. In the last several years, there has been a tremendous growth in the application of DTMs, not only in the traditional fields of geography, surveying and mapping, and earth and environ mental sciences, but also in landscape design, biodiversity analysis, environmental impact analysis and site selection for telecommunication facilities.
当DEM 创建之后，等高线、剖面图、不同表面之间的方量和三维可视化变得可用。在过去几年里，
DTM 的应用得到了显著的增长，不仅仅是在传统的地质、测绘，地球与环境科学领域，在景观设计、生物多样化分析、环境影响分析和通讯设备选址方面也得到了应用。
Unit 26 Applications of GIS
Due to increasing complexity of the real world situations, more challenges emerge in knowing about theprecious earth and also in planning and decision making processes.
由于现实日益复杂的现实世界的情况，关于地球的精确规划和决策的过程出现了更多的挑战。GIS is nowadays considered as an important tool in planning and decision making. It has been found applied in many fields, such as cadastral mapping, land use planning, forestry, wildlife management, infrastructure planning, zoning, military, environ mental monitoring, network planning, facility selecting, archaeology, agriculture, business marketing and sales, banking, health and human services, landscape architecture, libraries and museums, marine, coast, and oceans, media, mining and earth sciences, petroleum, retail business, state and local government, transportation.
GIS 现信被认为是一个在规划和决策制定上的重要工具。它被发现用于很多个领域，比如地籍图制作，土地利用规划，林业，野生动植物管理，基础设施规划，区域划分，军事，环境监测，网络规划，设备选择，考古学，农业，企业市场营销和销售，银行业，健康与人类服务业，园林景观，图书馆和博物馆，海事，海岸和海洋，媒体，矿业和地球科学，石油，零售业，国家和地方政府，运输业。Some of the advanced applications at present involve air traffic monitoring, road navigation, crime analysis, and so on. At present, GIS has become the accepted and standard means of utilizing spatial data. Likewise, the use of spatial data is growing very rapidly in diverse fields.
目前更深层次的应用包括航空交通监测，道路导航，犯罪分析等等。目前，GIS 成为利用空间数据的公认的标准方法。同样的，空间数据在多种领域的利用也在迅速的增长This ability to incorporate spatial data, manage it, analyze it, and answer spatial questions is the distinctive characteristic of a geographic information system. Mapmaking and geographic analysis is not new, but GIS makes it possible to do this type of work faster and more efficiently because of the power and ease of using modern computers. It allows virtually anyone to create a map to help explain historic events, plan for the future, and predict outcomes. The following examples explain the application fields of GIS.组织、管理、分析空间数据并且解决空间问题的能力是GIS 系统的一个显著的特征。地图制作和地理分析并不是新知识，但是因为现代计算机的力量和方便，GIS 能够使更快速、更高效地完成这样的工作成为一种可能。
Environment:
Environ mental fields have long used GIS for a variety of applications that range from simple inventory and query,to map analysis and overlay,to complex spatial decision making systems环境领域长期在各种领域应用GIS，范围涉及从简单的库存和查询范围到地图分析和叠加，再到复杂地空间决策系统。Examples include: forest modeling, air/water quality modeling and monitoring, environ mentally sensitive zone mapping, analysis of interaction between economic, meteorological, and hydrological & geological change. Typical data input into an environmental GIS include: elevation, forest cover, and soil quality and hydrogeology coverage. In many cases environmental GIS are used so that environmental considerations can be better incorporated into socioeconomic development enabling a balance between the two.
包括下面的例子：森林建模，空气/ 水质量建模和监测，环境敏感区制图，经济交叉分析，气象学，水文和地质变化。输入到环境地理信息系统里的象征性的数据包括：高程，森林覆盖，土壤推土机和水文地质覆盖。在很多情况下，环境地理信息系统被应用，所以环境因素能够很好地与社会经济学发展相结合并且能够达到两者之间的平衡。
Infrastructure and Utilities:
GIS technologies are also widely applied to the planning and management of public utilities. Organizations dealing with infrastructure and public utilities find GIS a powerful tool in handling aspects such as planning, decision support, customer service, regulatory requests, standardization of methods, and graphics display.
GIS 技术在规划和管理公共事业方面的应用也非常广泛，基础设施和公用事业处理组织发现GIS 在处理某些方面的问题的时候是一个有力的工具，比如规划，决策支持，客户服务，管理要求，方法标准化和图表显示。
Typicaluses include management of the following services: electric, gas, water, roads, telecommunication, storm sewers, T V/FM transmitting facilities, hazards analysis, and dispatch and emergency services. Typical data input includes street network, topographic data, demographic data and local government administration boundary.
典型的应用包括以下设施的管理：电，燃气，水，公路，交通，排水管道，电视/ 电台发射设备，危险分析，调度和应急服务。输入的典型数据包括街道网，地形数据，人口统计数据和地方政府的管理边界。
Computer Cartography:（计算机的地图制作）
The growth of computer-assisted cartography (CAC) has been largely dependent on the development of vector based GIS. With the help of GIS, cartographic tasks such as thematic overlays of information, map projections, and map sheet layouts can be performed much more conveniently. Continually updated geographic databases provide an easy way to produce new map editions. Automated mapmaking and virtual map images have replaced traditional paper maps in many applications.计算机辅助制图技术的成长很大依靠基于GIS 的矢量的发展。在GIS 的帮助下，制图任务像专题信息的叠加，地图投影和单张地图的布局能够更方便地进行。持续地更新地理数据库为生产新地图的版本提供了一个简单方式。自动制图和地图图像在很多应用领域取代了传统的纸质地图。
Web based maps have made general purpose navigation far more accessible to the public. However, manually digitized paper maps remain the primary form of data input in an automated cartography GIS. Scanned maps are also often used.
以一般地导航为目的基于网络的地图对于公众更为方便。然而，人工数字化纸质地图仍然是将数据输入到一个自动成图地理信息系统的主要形式。扫描地图也也经常用到。
Land Information:
GIS has aided management of land information by enabling easy creation and maintenance of data for land records, land planning and land use. In particular, a flourishing number of municipal governments have started to implement GIS to help manage their land information. GIS makes input, updates, and retrieval of data such as tax records, land use plan, and zoning codes much easier than during the paper map era. IS 通过轻松创建和维护土地记录，土地规划和土地利用数据来帮助管理土地信息。特别的，大量的市政府开始应用GIS 来帮助管理他们的土地信息。GIS 使输入，更新，恢复诸如纳税记录，土地利用规划，和区域编码比纸质地图时代更加容易。
Typical uses of GIS in land information management include managing land registry for recording titles to land holdings, preparing land use plan and zoning maps, cadastral mapping, etc. Input of data into a land information GIS includes: political and administrative boundaries, transportation, and soil cover.
GIS 中在土地信息管理中的典型应用包括为地产权益，管理土地登记，准备土地利用规划和地图分区，地图制作等。输入到一个土地信息系统中的数据包括：行政和管理区划，交通运输和土地覆盖。Engineering Pipeline: （工程管道）
Competitive pressure and regulatory constraints are placing increasing demands on pipeline operators to function in an efficient, safe, and responsible manner. Responding to these demands requires accessibility to information regarding geographically distributed assets and operations.
竞争压力和监管机制对管道管理者高效、安全、合理的行使职责，提出了更高的要求，为了响应这些需求，需要获得有关地理上分散的资产和业务的信息。
GIS technology facilitates the organization and management of data with a geographic component. It also eases data acquisition and utilization. GIS provides pipeline operators in companies such as Shell International with improved capability to manage pipeline integrity, improved efficiencies in pipeline operations, and improved response to business development opportunities.
GIS 技术通过地理组件技术促进了数据的组织和管理，它也使数据的获取和应用更容易。GIS 为公司里的管道运营商提供像壳（ciao）牌国际一样的管道完整性管理的改进能力，提高流水线作业的效率，并改善响应业务发展能力。
Engineering Surveying:工程测量
Surveyors and engineers understand the importance of geographic data. Surveyors use precise instruments, procedures, and computations to accurately locate and define geographic features while conducting field surveys that range from cadastral to engineering construction layout. Engineers design and build structures
and infrastructures on geography measured by surveyors.
测量员和工程师了解地理数据的重要性，从地籍测量到工程施工放样，测量员在进行野外测量时采用高精度的仪器，流程和计算方法来精确定位并确定地理特征，工程师根据测量员测量的地形设计和建造结构及基础设施。
GIS provides the tools to help surveyors in thousands of state and local governments, including Marion County, Oregon, to integrate a variety of data sources and types, maintain and manage inventories, and visualize data and related information using dynamic maps. GIS is also used for real estate litigation support by providing modeling and analysis.
在数以千计的国家政府和地方政府，包括马里恩县，俄勒冈州，GIS 提供工具来帮助测量员，它将多种数据来源和数据类型融合到一起，维护和管理目录，并采用动态地图来显示数据和相关信息，GIS 通过提供模型和分析为房地产诉讼提供支持。
Location Services:定位服务
As the global community increasingly becomes more mobile, locating people, places, and things while deriving useful information from raw locations has never been more important. Governments and businesses managing enterprise wide spatial data repositories require expedient options to disseminate critical business data to personnel and resources in the field; mobile consumers increasingly demand convenient commercial location services that enhance mobile lifestyles; and legislation in some regions of the world forces solution providers to quickly develop highly reliable, trusted, and always available emergency service applications, ensuring public safety responses for all location aware mobile devices and entities. Many companies, including Air Zip, Signal Soft, and Traffic Station, are assisting ESRI in bringing this technology to businesses and governments throughout the world.
随着全球社会变得更加流动，相对初始位置定位人、地点和事件，同时获取有用信息从未变得像现在这样重要。政府和企业对企业范围内的空间数据库的管理，对关键的商业信息传递给人力资源传递提供了有用的选项。手机消费者对提高移动生活方式的便利化、商业化的定位服务提出了更多的需求；世界上一些地区的法律强迫解决方案供应商开发高度可靠，可信赖的，并且随时提供紧急服务的应用，以确保公众对所有位置感知移动设备和实体的安全响应。许多公司，包括Air Zip, Signal Soft 和Traffic Station，帮助ESRI 将这项技术带入商业、政府直至整个世界。
Mining and Earth Sciences:矿业和地球科学
GIS creates efficiency and productivity opportunities in all aspects of mineral exploration and mining. GIS enables mineral geologists and mine operators to mine intelligently, efficiently,competitively, safely, and environmentally. GIS provides the framework to acquire, develop, and interpret the complex spatial and tabular data sets used for mining and the earth sciences.
GIS 在矿产资源勘查和开采的所有方面创造了提高效率和生产力的机会。地理信息系统，使矿产地质学家和矿商智能地，高效地，有竞争力地，安全地，环保地挖掘，GIS 提供了获取、开发和解译复杂的空间属性数据用于采矿和地球科学的框架。
Mapping, spatial concepts, and time/space operations technology are absolutely essential to effective mining. Natural Resources at a time when the earth’s resources are being taxed like never before, natural resource managers are discovering the power of GIS to help them make crucial decisions. GIS is helping development and conservation communities find common ground by providing a framework for the analysis and discussion of resource management issues.
制图、空间概念和时/ 空操作技术对于高效的开采是十分必要的。地球的自然资源从未有像现在这样大的负担，自然资源的管理者发现了GIS 帮助他们制定关键决策的作用。GIS 提供了分析和讨论
资源管理话题的框架，帮助找到社会中发展和保护的共同点。
Companies and organizations, including the Nature Conservancy, the Environmental Protection Agency, Chevron, and the Department of Fish and Wildlife, are unleashing the power of GIS to manage natural resources.
各种公司、机构包括自然保护机构、Chevron 环境保护组织、和鱼类和野生动物部，正在释放地理信息系统管理自然资源的动力。
Transportation:交通
In the transportation industry,geographic analysis is the key to making better decisions.
在交通运输业，地理分析对制定更好决策起关键作用。GIS serves three distinct transportation needs: infrastructure management, fleet and logistics management, and transit management. Transportation professionals, such as the New York Department of Transportation, the Maryland State High way Administration, and the city of Reykjavik, Iceland, use GIS to integrate mapping analysis into decision support for network planning and analysis, tracking and routing, inventory tracking, route planning and analysis, and more.
GIS 满足三种不同的交通需求：基础设施管理、船泊与物流管理和运输管理。在交通运输领域，例如纽约交通部、马里兰高速路管理局、雷克雅未克市和冰岛，用GIS 将地图分析融入到为交通网络规划分析、跟踪路由、追踪存货、路径规划分析等更多提供支持的决策中。
Unit 28 Fundamentals of Remote Sensing （遥感的基础）
What Is Remote Sensing?
For the purposes of understanding the concepts of remote sensing, the following definition should be given first: [CCRS, 2003]“Remote sensing is the science ( and to some extent, art) of acquiring information about the Earth’s surface without actually being in contact with it . This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applyin g that information.”为了了解遥感的概念,给出下面的定义: （加拿大遥感中心，2003）“遥感是在不直接接触的情况下，获取地球表面信息的一门科学（某种程度上可以称之为艺术）。这是通过感知、记录和处理、分析,并应用反射或者发出的能量信息实现的。”
In much of remote sensing, the process involves an interaction between incident radiation and the targets of interest. This is exemplified by the use of imaging systems where the following seven elements are involved. Note, however that remote sensing also involves the sensing of emitted energy and the use of non-imaging sensors (Figure 1).
在绝大多数的遥感中, 该过程包括入射辐射和感兴趣区域的互动。这个可以在使用了如下七个要素参与的成像系统中得到例证。注意,遥感也包括了辐射能量的感知和使用非成像传感器。
1. Energy source or illumination (A) —the first requirement for remote sensing is to have an energy source which illuminates or provides electromagnetic energy to the target of interest. The primary source of electromagnetic energy that illuminates natural targets is the sun, although Earth itself can emit geothermal and man-made energy .Electromagnetic radiation is a form of energy.
1. 能量源或照明——遥感的第一个需求是有一个能够发光的或为感兴趣目标提供电磁能量一个能量源。能够照亮目标的电磁能量的主要来源是太阳，尽管地球本身能够发出地热和人造能量。电磁辐射是能量的一种形式。
The fundamental unit of electromagnetic radiation is the photon. The photon, which has energy but no mass, moves at the speed of light. The wave theory of light has light traveling in wavelike patterns, with its energy characterized by its wavelength or frequency.
电磁辐射的基本单位是光子。光子具有能量但不集中，以光速移动。光波理论是光以波浪形式行进，用波长或频率来表现能量特征。
The speed of light is generally considered to be 300, 000km/ s. Figure 2 shows the electromagnetic spectrum, with wavelengths ranging in size from the very small (cosmic, gamma, and x-rays) to the very large (radio and television) . In most remote sensing applications, radiation is described by its wavelengths, although those using microwave (Radar) sensing have traditionally used frequency instead to describe these mush longer wavelength signals.
光的传播速度通常被认为是300000km/s. 图 2 显示了电磁光谱波长范围从非常小（宇宙射线、伽马射线和X -光）到非常大（无线电波）。在遥感的大多数应用中，辐射通常用他的波长来表示，尽管那些正在使用的微波（雷达）遥感历来采用频率来代替波长描述那些波长更长的信号。
2. Radiation and the atmosphere (B) —as the energy travels from its source to the target, it will come in contact with and interact with the atmosphere it passes through .This interaction may take place a second time as the energy travels from the target to the sensor.
2. 辐射和大气——随着能量从源头到目标的移动，它将会与它经过并接触到的大气相互作用。这种作用随着能量从目标到传感器的传播将会再次发生。
3. Interaction with the target (C) —once the energy