GPS中英文翻译

Summarizing The Global Positioning System Abstract:Global Positioning System is based on the background of the United States

Department of Defense.It is designed,invested,developed,and operated by the United States Department of Defense ,GPS is a satellite-based positioning and time transfering GPS positioning function has a wide range of applications in the modern measurement and a more modern building.GPS-RTK technology is also widely used in modernization building, and now GPS has also been shown to be an important civilian communities of interest, and increasingly wide range of applicated.

Keyword:GPS,Locating，RTK，Lay out，Survey

1.Background

The 50s, the former U.S.S.R has not launched humanities first artificial earth

satellite, the American scientists in along its track research in, had discovered the

Doppler shift phenomenon, and has facilitated Doppler satellite navigation posi- tioning

system completing using this principle, has obtained the enormous success in the

military and the civi aspect, was in a navigation localization history leap, our country

once has also introduced many Doppler receiver, applied to the island association

measured, the Earth explored and so on the applied to the island association measured,

the Earth explored and so on the domain. But because Doppler satellite orbit highly low,

signal-carrier frequency low, the track precision enhances with difficulty, causes the

pointing accuracy lowly, satisfies the geodetic survey or the project survey request, is

more impossible to use in the astronomy Earth dynamics research. In order to enhance

the satellite positioning the precision,US started from 1973 to prepare for construction

global positioning system GPS (Global Positioning System).After has entered the plan

proof, the system test stage,started in 1989 to launch the official work satellite,and

completely completed in 1994, investment use. The GPS system spaceartially is

composed by twenty one satellites, evenly distributes in six orbit, the ground level is

20,000 Kilometers, the inclination of orbit is 55, the flat heart rate approximately is 0,

the week contract is 12 hours, the satellite to the earth launching two wave bands

intelligence signals,the intelligence signal frequency respectively is 1575.442 mega

cycles per second (the L2 wave band), on the satellite has installed the precision very

high atomic clock, guarantees the frequency the stability, modulates in the carrier has the expression satellite position the broadcast star experience, use in the range finder C/A code and P yard, as well ad other system information, can in the global scope, to willfully multi-user provide the high accuracy, all-weather, is continual, real-time three dimensional measures fast, the three dimensional localization and the time service.

The GPS system control section by is located in the American foundations of the states 5 monitoring stations to be composed, these stand did not ask breaks Carries on the observation to GPS satellite, and will calculate and the forecast information by the infusion stands renews to the satellite information.

The GPS system user is extremely covert, it is one kind of one-way system,the user only receives but does not need the transmitting message, and therefore user' s quantity also is not limited. Although GPS is the unification starts is, but very quantity also is not limited. Although GPS recei ver and processing software emerge in abundance. At present the receiver which appears in the Chinese market mainly has ROGUE,ASHTECH, TRIMBLE, LEICA, SOKKIA, TOPCON and so on.. Can carry on the observation to two frequencies the receiver to be called the double frequency receiver, only can carryon the observation to a frequency the receiver to become the inference. Says regarding the mapping user, GPS has caused the revolutionary change in the mapping domain, at present, in the scope several thousand kilometers controls network, in the precision from hundred to the millimeter level localization, generally all GPS took the first choice method, is day by day mature along wi th the RTK technology, GPS started to decimeter and even a centimeter level layout, domain seepage and so on high accuracy dynamic localization.

The international GPS geodetic survey served IGS with Earth dynamics from 1992, has established many data storage and the processing center in the whole world, year to year observed a station with hundred, our country has also set up Shanghai Y u Shan, Wuhan, Xian, Taiwan and so on many year to year measuring platforms station, these stations observation data passed on every day through the internet net to US' S data storage center, IGS also nearly real-time synthesizes various data processing center the result, and the participant international earth rotation served the IERS global coordinates reference system maintenance and the earth rotation parameter issue. The user also may

free on-line obtain product and so on observation data and precise star experience from internet.

The GPS system real-time navigation pointing is very high,US hasimplemented the so-called SA policy in 1992, namely reduces the broadcaststar to undergo the star posi tion precision, reduces the star clock to change thepositive number the precision, adds on the high frequency vibration to thesatellite datum frequency (to cause false distance measuring accuracy to reducewith phase ), latter has implemented the A-S policy, soon P yard change is Y yardnamely further limi ts to the precise false distance survey, but American military and special permission user not these polices influences, but US in order to obtain the bigger commercial interest, these policy ends are cancelled.

2.GPS localization principal

The GPS receiver may receive and use in the time service accurately to the nanosecond level time information; will use in to forecast the future for several months the satellite to locate the summary position forecast star experience; Uses in calculates when the localization to need the satelli te coordinates the broadcast star experience, the precision is (each satellite is different several meter to several dozens meters~changes as necessary); As well as GPS system information, like satellite condition and so on.

The GPS receiver may obtain the satellite sign to the code to the receiver distance, because includes the receiver satellite clock the error and the atmosphere propagated error, therefore is called the false distance. The false distance obtains which to the OA code is called the UA code false distance, the precision approximately is about 20 meters, obtains the false distance to P yard to be called P yard false distance, the precision approximately is about 2 meters.

The GPS receiver to the satellite signal which receives, carries on the decoding or uses other technologies, will modulate after the carrier the information removes, will be allowed to restore the carrier. Strict says, the carrier phase should be called the carrier beat frequency phase, it is receives produces the Doppler shift influence satellite signal carrier phase and receiver this machine vibration difference of the signal phase. Generally experience Yuan time which determined in the receiver clock surveyed, maintains to the satellite signal track under, may record the phase change value, but

starts time the observation receiver and the satellite oscillator phase change value is does not know, namely misty degree of whole week, only can calculate in the data processing as the parameter solution. Phase observation value precision high to millimeter, but the premise is solves misty degree of whole week, therefore only has when the relative localization, and has a section continuously observes the value can use the phase observation value, but must achieve meters down to themillimeter level also only to be able to use the phase observation value.

According to the locate mode, the GPS localization divides into the simple point localization and the relative localization (difference localization). The simple point localization is according to a receiver observation data determined the receiver position the way, it only can use the false distance view survey, may use in Chef Chuan and so on the summary navigation localization. The relative localization (difference localization) is according to two above receivers observation data determined between the observation point the relative position method, it already may use the false distance view survey also to be possible to use the phase view survey, the geodetic surveyor the project survey should use the phase observation value to carryon the relative localization. Has contained the satellite and receiver ZhongChai, the atmospheric dissemination in the GPS view survey retards, error and so on multipart effect, when localization error the influence, when carries on the relative localization the majority of public errors are counterbalanced or weaken, therefore the pointing accuracy greatly will enhance, the double frequency receiver will be allowed to act according to two frequencies in the view survey counterbalance atmosphere the ionosphere-path error main part, will request high in the precision, between the receiver the distance wi11 be farther when (atmosphere will have obvious difference), will be supposed to select the double frequency receiver.

When localization observation, if the receiver is opposite to the earths surface movement, then is called the dynamic localization, like uses in summary navigation localization the and so on Chef Chuan precision is 30-100 meter false distance simple point localization, either uses in the city vehicles navigation localization rice level precision false distance difference localization(RTK), the real-time difference localization needs the data chain real-time transmits two or many stations observation

data calculates together.

When localization observation, if the receiver is opposite to the earths surface static, then is called the static localization, when carries on controls the net observes, generally selects this method by several receivers also to observe, it can maximum limit display GPS the pointing accuracy,special-purpose Yu Zheizhong the goal receiver is called the earth receiver,is in the receiver a performance best kind. At present, GPS already could achieve the earths crust performance observation the precision request, IGS year to year the measuring platform already can constitute millimeter level the global coordinates frame.

3.RTK technologies

The conventional GPS measuring technique, like the static state, the fast static state , the dynamic survey all~eed afterwards to carryon the solution to calculate can obtain a centimeter level the precision, but RTK is can real-time obtain the centimeter level pointing accuracy in the open country the measuring technique, it has used the carrier phase dynamic real-time difference (Real-timekinematics) the method, is the GPS application significant milestone, its appearance for the project layout, the terrain mapping, each kind of control survey has brought the new dawn, enormously enhanced the field operation work efficiency.

The high accuracy GPS survey must use the carrier phase observation value,the RTK localization technology, it can real-time provide in assigns in the coordinate system the three dimensional localization result, and achieves the centimeter level precision. Under the RTK work pattern, the datum stands through the data chain transmi ts together its observation value and the survey station coordinates information for the mobile station. Mobile stands not only receives the data through the data link which stands from the datum, but also must gather the GPS observation data, and composes the difference observation value in the system to carryon the real-time processing, simultaneously produces the centimeter level localization result, a lasted. The mobile station may be at the static condition, also may be at the state of motion; May first carryon the initialization after the fixed point to enter the dynamic work again, also may under the dynamic condition directly opening machine,and completes the

week fuzziness search solution under the dynamic environment. After end knows the number solution to be fixed, then carries on each calendar Yuan real-time processing, so long as can maintain four above satellites phases observation value the track and the essential geometric figure ,then the mobile station may produce the centimeter level localization result as necessary.

The RTK technology key lies in the data processing technology and the data transmission technology, when the RTK localization requests the datum station receiver real-time the observation data (false distance observation value, phase observation value) and the know data transmission for the mobile station receive, the data quantity quite big, generally all requests 9,600 bauds rate, this in on radio is not difficult to realize.

4.The application of RTK

(1)Each kind of control survey

The traditional geodetic survey, the project control survey uses the triangular net, the line-network method executes measured, not only requires a lot of work time-consuming, request Indivisibility, moreover the precision distribution non-uniformity, also at the field operation did not know how the precision, does use conventional the GPS static state survey, the fast static state, the false dynamic method, survey in the process at field operation not to be able real-time to know the pointing accuracy, after if surveys completes, after returns to house processing to discover the precision does no t gather the request, but also must return measured, but uses RTK to carryon the control survey, can real-time know the pointing accuracy, if the fruits and cakes position precision request has satisfied, the user was allowed to stop observing, how moreover knew the observation quality, This may greatly enhance the work efficiency. If uses in the road control survey RTK,electronic circuit control survey, the hydraulic engineering control survey, the geodetic survey, then not only may greatly reducethe manpower intensi ty, the economical expense, moreover greatly enhances the working efficiency,measured a control point may complete in several minutes even several seconds.

(2)Terrain mapping

In the past measured when topographic diagram generally first must in measure area establishment chart root control point, then on chart root control point top carriage entire station meter or altazimuth coordination small flat panel mapping, now develops the field operation with the entire station meter and the electronic hand coordination thing code, uses big scale mapping software to carryon the mapping, even develops recent field operation electron dull mapping and so on, all requests in the survey station to measure all around terrain landform and so on department point, these points all wi th survey station indivisibility, moreover generally requests at least 2-3 person to operate, needs when puts together the chart once the precision not to gather the request also to obtain the field operation to return measured,when now uses RTK, only needs a person to carry the instrument in on the terrain landform department point dull 12 second kinds which must measure, and simultaneously inputs the characteristic code, through hand book may real-time know the position precision, after measured a region returns to in the room, may output the topographic diagram by the specialized software connection which requests, like this uses RTK only to need a person to operate,does not request a between indi visibi Ii ty, greatly enhanced the working efficiency, uses the RTK coordination electron hand book to be allowed to survey each kind of topographic diagram, I ike the ordinary mapping, the track，line strip the shape topographic diagram surveying, road pipeline topographic diagram surveying, coordinates the depth-finding device to be allowed to use in to measure the reservoir topographic diagram, Navigation sea mapping and so on.

(3)Layout

Layout surveys an application branch, it request through the certain method to use the certain instrument the spot position which artificial designs in really for to demarcate, in the past used the convention layout the method very many, like the altazimuth junction met layout, when the ent ire 50 station meter and so on, generally layout a design position, often needed the back and forth bile target, moreover took 2-3 person to operate, simultaneously also requested the indivisibility situation in the process to be good, in the production application the efficiency was not very high, sometimes layout encountered the difficult situation to be able to draw support fromYu Hindu the method

to layout. Sometimes, if uses the RTK technology layout, only must the spot position coordinates which designs input to the electron hand, is carrying the GPS receiver, it can remind you to walk to want to layout a position, both rapid and convenient, because GPS is comes directly through the coordinates layout,the precision is very high, thus can greatly enhance efficiency, also only needs a person to operate.

5. The application of GPS

GPS offers for military and makes a reservation and sets up accurately at first, it is still controlled by the American military so far. Military GPS products is it confirm and follow in field advancing soldering and coordinating of equipment in to used for mainly, the gunship for the sea navigates, offers the position and navigation information for military aircraft.

(1) The GPS system use is extensively

At present, application, GPS of system very extensive already, we can use GPS signal can carryon sea, empty and navigation of land, the guidance of the guided missile, earth measurement and accurate localization of project measurement., transmission of time and measurement of the speed,etc.For survey and draw field,GPS satellite fix technology is it set up nationwide earth measurement of high accuracy control network to use for already, determine global dynamic parameter of earth;Used for setting up land marine earth measurement datum, unite and examines and surveys and draws in the ocean the high-accuracy island land;Used for moni toring plate motion state of the earth and the earths crust deformation;Used in project measure,is it set up city and project control main means of network to become For determine Aero-Space photograph camera position in the twinkling of an eye, realize for a small amount of ground control or there is no aerial survey controlled in region to become and pursue fast, technical revolution causing the geographical information system,global environmental remote to follow their monitor.A lot of commerce and government organs use GPS equipment to follow their vehicle position;This generally needs to draw support from

wireless communication technology.Some GPS receiver integrated radio, radio telephone move data terminal is it meets need, motorcade of management to come.

(2) Appearance of the resource environment of pluralistic space

At present, GPS, GLONASS, INMARSAT waits for the system to all possess and navigate to orient the function, formed the pluralistic room resource environment. This pluralistic space environment ,has impelled and fumed a piece of common tactics internationally and folly, namely on one hand fully utilize the existing system, on the other hand prepare to establish folk GNSS system actively ,by the tome around the2010,GNSS folk system build our purely, the woke world form the tendency that GPS/GLONASS/GNSS stood like the legs of a tripod, could get rid of the reliance on the single system fundamentally, form owning in common, security resource environment which world shares of worlk.World can is it is it use realm at most as single navigation means to navigate satelli te to enter. This international and folk strategy, there id influence and force U.S.A to use the policy to make more omen adjustment to its GPS converselu. Inaword , because of the establishment of the resource environment of pluralistic space ,have created an unprecedented gapped international environment for the development and application of GPS.

(3) Develop gaps industry

GPS Will form industrialization like the automobile, wireless communication at present in the future, US>A strengthen wide area systematic WAAS (namely wide area is it revise date chain transfer to already, it make geostationary satellite it have C? A yards of function too, form wide area the GPS strengthen system of) plan international standard of developing into of. Some units produce car-mounted GPS system too at present in our country.For GPS industry of developing our country, already China GPS project centrehas been established in Wuhan.

全球定位系统概述

摘要：全球定位系统是以美国国防为背景，由美国国防部设计、投资、开发、和运行的。GPS是以卫星定位和时间传输为基础，GPS定位功能在现代测量和现代建设中有较为广泛的应用，GPS-RTK技术也在现代化建设中有着广泛的应用，现在GPS 也已经显示出对平民社区的一种重要的利益，且其应用范围越来越广泛。

关键词：GPS、定位、RTK、放样、测量

1、背景

五十年代末，原苏联发射了人类的第一颗人造地球卫星，美国科学家在对其的跟踪研究中，发现了多普勒频移现象，并利用该原理促成了多普勒卫星定位导航系统的建成，在军事和民用方面取得了巨大的成功，是导航定位史上的一次飞跃，我国也曾引进了多台多普勒接收机，应用与海岛联测、地球勘探等领域。但由于多普勒卫星轨道高度低、信号载波频率低，轨道精度难以提高，使得定位精度较低，以满足大量测量或工程测量的要求，更不能用于天文地球动力学研究。为了提高卫星定位的精度，美国从1973 年开始筹建全球定位系统GPS创(Global Positioning System)。在进行了方案论证、系统试验阶段后，于1989 年开始发射正式工作卫星，并于1994 年全部建成，投入使用。GPS系统的空间部分由21颗卫星组成，均分布在6个轨道上，地面高度为20000余公里，轨道倾角为55度，扁心率约为0，周期约为 12小时，卫星向地面发射两个波段的载波信号，载波信号频率分别为1575.442兆赫兹(L1波段)和1227.6兆赫兹(L2波段)，卫星上安装了精度很高的原子钟，以确保频率的稳定性，在载波上调制有表示卫星位置的广播星历，用于测距的C/A 码和P码，以及其它系统信息，能在全球范围内，向任意多用户提供高精度的、全天候的、连续的、实时的三维测速、三维定位和授时。

GPS 系统的控制部分有设在美国本上的5个监控站组成，这些站间不断地GPS 卫星进行观测，并将计算和预报的信息由注入站对卫星信息更新。

GPS系统的用户是非常隐蔽的，它是一种单程系统，用户只接收而不必发射信号，因此用户的数量也是不受限制的。虽然GPS系统一开始是为军事目的而建立的，但很快在民用方面得到了极大的发展，各类GPS 接收机和处理软件纷纷涌现出来。能对两个频率进行观测的接收机称为双频接收机，只能对一个频率进行观测的接收机称为单频接收机，他们在精度和价格上均有较大区别。对于测绘界的用户而言，

GPS己在测绘领域引起了革命性的变化，目前，范围上数公里至几千公里的控制网或变形监测网，精度上从几百至毫米级的定位，一般都将GPS作为首选手段，随着RTK 技术的日趋成熟，GPS一开始向分米乃至厘米级的放样、高精度动态定位等领域渗透。

国际GPS大地测量和地球动力学服务IGS自1992 年起，己在全球建立了多个数据存储及处理中心，和百余个常年观测的台站，我国也设立了上海余山、武汉、西安、拉萨、台湾等多个常年观测台站，这些台站的观测数据每天通过INTERNET网传向美国的数据存储中心，IGS还几乎实时地综合各数据处理中心的结果，并参与国际地球自转服务IERS的全球坐标参考系维护及地球自转参数的发布。使用者也可免费从INTERNET网上取得观测数据及梗米数据等产品。

GPS系统的实时导航定位精度很高，美国在1992年起实行了所谓的SA政策，即降低广播星历中卫星位置的精度，降低卫星钟改正数的精度，对卫星基准频率加上高频的抖动(使伪距和相位的量测精度降低)，后又实行了A-S政策，即将P码改变为Y码，即对精密伪距测量进一步限制，而美国军方和特许用户不受这些政策的影响，但美国为了获得更大的商业利益，这些政策终将被取消。

2、GPS定位原理

GPS 接收机可接收到可用于授时的准确至纳秒级的时间信息，用于预报未来几个月内卫星所处概略位置的预报星历:用于计算定位时所需卫星坐标的广播星历，精度为几米至几十米(各个卫星不同，随时变化);以及GPS系统信息，如卫星状况等。

GPS接收机对码的量测就可得到卫星到接收机的距离，由于含有接收机卫星钟的误差及大气传播误差，故称为伪距。对OA码测得的伪距称为UA码伪距，精度约为20米左右，对P码测得的伪距称为P码伪距，精度约为2 米左右。

GPS接收机对收到的卫星信号，进行解码或采用其它技术，将调制在载波上的信息去掉后，就可以恢复载波。严格再言，载波相位应被称为载波拍频相位，它是收到的受多普勒频移影响的卫星信号载波相位与接收基本机振荡产生信号相位之差。一般在接收机钟确定的历元时刻量测，保持对卫星信号的跟踪，就可记录下相位的变化值，但开始观测时的接收机和卫星振荡器的相位初值是不知道的，起始历元的相位整数也是不知道的，即整周模糊度，只能在数据处理中作为参数解算。相位观测值得精度高至毫米，但前提是解出整周模糊度，因此只有在相对定位、并有一段连续观测值时才能使用相位观测值，而要达到优于米级的定位精度也只能采用

相位观测值。

按定位方式， GPS定位分为单点定位和相对定位(差分定位)。单点定位就是根据一台接收机的观测数据来确定接收机位置的方式，它只能采用伪距观测量，可用于车船等的概略导航定位。相对定位(差分定位)是根据两台以上接收机的观测数据来确定观测点之间的相对位置的方法，它既可采用伪距观测量也可采用相位观测量，大地测量或工程测量均应采用相位观测值进行相对定位。在GPS观测量中包含了卫星和接收机的钟差、大气传播延迟、多路经效应等误差，在定位计算时还要受到卫星广播星历误差的影响，在进行相对定位时大部分公共误差被抵消或削弱，因此定位精度降大大提高，双频接收机可以根据两个频率的观测量抵消大气中电离层误差的主要部分，在精度要求高，接收机间距离较远时(大气有明显差别)，应选用双频接收机。

在定位观测时，若接收机相对于地球表面运动，则称为动态定位，如用于车船等粗略导航定位的精度为30-100 米的伪距单点定位，或用于城市车辆导航定位的米级精度的伪距差分定位，或用于测量放样等的厘米级的相位差分定位(RTK)，实时差分定位需要数据连降两个或多个站的观测数据实时传输到一起计算。

在定位观测时，若接收机相对于地球表面静止，则称为静态定位，在进行控制网观测时，一般均采用这种方式由几台接收机同时观测，它能最大限度地发挥GPS 的定位精度，专用于这种目的的接收机被称为大地型接收机，是接收机中性能最好的一类。目前，GPS己经能够达到地壳形变观测的精度要求， IGS常年观测台站己经能构成毫米级的全球坐标框架。

3、RTK 技术

常规的GPS测量方法，如静态、快速静态、动态测量都需要事后进行解算才能获得厘米级的精度，而RTK 是能够在野外实时得到厘米级定位精度的测量方法，它采用了载波相位动态实时差分(Real-time Kinematic)方法，是GPS 应用的最大里程碑，它的出现为工程放样、地形测图，各种控制测量带来了新曙光，极大地提高了外业作业效率。

高精度的GPS测量必须采用载波相位观测值，RTK 定位技术就是基于载波相位观测值的实时动态定位技术，它能够实时地提供测站点在指定坐标系中的三维定位结果，并达到厘米级精度。在RTK 作业模式下，基准站通过数据链将其观测值和测站坐标信息一起传送给流动站。流动站不仅通过数据链接收来自基准站的数据，还

要采集GPS 观测数据，并在系统内组成差分观测值进行实时处理，同时给出厘米级定位结果，历时不到一秒钟。流动站可处于静止状态，也可处于运动状态;可在固定点上进行初始化后再进入动态作业，也可在动态条件下直接开机，并在动态环境下完成周模糊度的搜索求解。在整周未知数解固定后，即可进行每个历元的实时处理，只要能保持四颗以上卫星相位观测值的跟踪和必要的几何图形，则流动站可随时给出厘米级定位结果。

RTK 技术的关键在于数据处理技术和数据传输技术，RTK 定位时要求基准站接收机实时地把观测数据(伪距观测值，相位观测值及己知数据传输给流动站接收机，数据量比较大，一般都要求9600 的波特率，这在无线电上不难实现。

4、RTK 技术的应用

(1)各种控制测量

传统的大地测量、工程控制测量采用三角网、导线网来施测，不仅费工费时，要求点与点之间通视，而且精度分布不均匀，且在外业不知精度如何，采用常规的GPS静态测量、快速静态、伪静态方法，在外业测设过程中，不能实时知道定位精度，如果测设完成后，回到内业处理，发现精度不合要求，还必须返测，而采用RTK 来进行控制测量，能够实时知道定位精度，如果点位精度要求满足了，用户就可以停止观测了，而且知道观测质量如何，这样可以大大提高作业效率。如果把RTK用于公路控制测量、电子线路控制测量、水利工程控制测量、大地测量、则不仅可以大大减少人力强度、节省费用，而且大大提高工作效率，测一个控制点在几分钟甚至于几秒钟内就可完成。

(2)地形测量

过去测地形图时，一般首先要在测区建立图根控制点，然后在图根控制点上架上全站仪或经纬仪，配合小平板测图，现在发展到外业用全站仪和电子手薄配合地物编码，利用大比例尺测图软件来进行测图，甚至于发展到最近的外业电子平板测图等，都要求在测站长测四周的地形、地貌等碎部点，这些碎部点都与测站通视，而且一般要求至少2-3人操作，需要在拼图时一旦精度不合要求还得到外业去返测，现在采用RTK 时，仅需一人背着仪器在要测的地形地貌点呆上一二秒钟，并同时输入特征编码，同过手薄可以实时知道点位精度，把一个区域测完后回到室内，由专业的软件接口就可以输出所要求的地形图，这样用RTK仅需一人操作，不要求点与

点间通视，大大提高了工作效率，采用RTK 配合电子手薄可以测设各种地形图，如普通地测图、铁路线路带状地形图的测设，公路管线地形图的测设，配合测深仪可以用于测水库地形图，航海海洋测图等等。

(3)放样

放样是测量的一个应用分支，它要求通过一定方法，采用一定仪器把人为设计好的地位在实地给标定出来，过去采用常规的测量放样方法很多，如：经纬仪交会放样，全站仪的边角放样等等，一般要放样出一个设计点位时，往往需要来回移动目标，而且要2-3人操作，同时在放样过程中还要求点与点间通视情况良好，在生产应用上效率不是很高，有时放样中遇到困难的情况很复杂，要借助于很多方法才能放样，如果采用RTK技术放样时，仅需把设计好的点位坐标输入到电子手薄中，背着GPS 接收机，它会提醒你走到要放样点的位置，即迅速又方便，由于GPS是通过坐标来直接放样的，而且精度很高也很均匀，因而在外业放样中效率会大大提高，且只需一人操作。

5、GPS的应用

GPS 最初就是为军方提供精确定位而建立的，至今它仍然由美国军方控制。军用GPS产品主要用来确定并跟踪在野外行进中的士兵和装备的坐标，给海中的军舰导航，为军用飞机提供位置和导航信息等。

(1) GPS系统用途广泛

目前，GPS系统的应用己经十分广泛，我们可以应用GPS信号进行海、空和陆地的导航，导弹的制导，大地测量和工程测量的精密定位，时间的传递和速度的测量等。对于测绘领域， GPS卫星定位技术己经用于建立高精度的全国性的大地测量控制网，测定全球性的地球动态参数;用于建立陆地海洋大地测量基准，进行高精度的海岛陆地联测以及海洋测绘;用于监测地球板块运动状态和地壳形变:用于工程测量，成为建立城市与工程控制网的主要手段。用于测定航空航天摄影瞬间的相机位置，实现仅有少量地面控制或无地面控制的航测快速成图，导致地理信息系统、全球环境遥感监测的技术革命。许多商业和政府机构也使用GPS 设备来跟踪他们的车辆位置，这一般需要借助无线通信技术。一些GPS接收器集成了收音机、无线电话和移动数据终端来适应车队管理的需要。

(2)多元化空间资源环境的出现

目前，GPS，GLONASS，INMARSAT等系统都具备了导航定位功能，形成了多元化的空间资源环境。这一多元化的空间资源环境，促使国际民间形成了一个共同的策略，即一方面对现有系统从分利用，一方面积极筹建民间GNSS系统，待到2010年前后，GNSS纯民间系统建成，全球将形成GPS/GLONASS/GNSS三足鼎立之势，才能从根本上摆脱对单一系统的依赖，形成国际共有、国际共享的安全资源环境。世界才可进入将卫星导航作为单一导航手段的最高应用境界。国际民间的这一策略，反过来有影响和迫使美国对其GPS 使用政策做出更开放的调整。总之，由于多元化空间资源环境的确立，给GPS的发展应用创造了一个前所未有的良好的国际环境。

(3)发展GPS产业

今后GPS 将像目前汽车、无线电通信等一样形成产业多元化。美国己经广域增强系统WAAS (即将广域差分系统中的发送修正数据链转为地球同步卫星发送，使地球同步卫星也具有C/A码功能，形成广域GPS增强系统)计划发展成国际标准。我国目前也有一些单位生产车载GPS 系统。为发展我国的GPS产业，武汉已经成立中国GPS工程中心。