1 卫星定位技术与方法 第一讲 袁林果 Email: lgyuan@163.com 西南交通大学测量工程系 卫星定位技术与方法——袁林果2005-2-25 2 课程概述 z目标：介绍GPS卫星测量基本原理及其应用 z PPT课件采用中英文结合方式 z在学习制定教材的基础上，依据学生的兴趣和个 人能力，学习内容和形式多样 z重点强调基本原理的理解和掌握 z其它要求：网上查阅GPS专业资料的能力；英文 阅读能力；独立完成作业、严禁拷贝 z成绩评定：平时成绩30%；期末考试70% 2 卫星定位技术与方法——袁林果2005-2-25 3 课程大纲 1.历史、发展和当前状况 2.坐标系统与时间系统 3.卫星轨道运动及GPS卫星的坐标计算 4. GPS卫星信号与传播 5. GPS观测量、观测方程及误差分析 6.绝对（单点）定位原理 7.相对（差分）定位原理 8. GPS测量实施及软件操作（实习） 9. GPS应用 卫星定位技术与方法——袁林果2005-2-25 4 References ? Textbook 周忠谟, 易杰军, 周琪. GPS卫星测量原理与应用（修订本）. 北京: 测绘 出版社, 1997 ? References 刘基余. GPS卫星导航定位原理与方法. 北京: 科学出版社, 2003 刘大杰. 全球定位系统(GPS)的原理与数据处理. 上海:同济大学出版社, 1999 B. Hofmann-Wellenhof, H. Lichtenegger, and J. Collins, GPS Theory and Practice, Fifth edition. Springer-Verlag, Wein, New York, 2001. Alfred Leick. GPS Satellite Surveying, 3rd Edition. John Wiley & Sons, Inc., Hoboken, New Jersey, 2003. NAVSTAR Global Positioning System Surveying. US Army Corps of Engineers. EM 1110-1-1003 3 卫星定位技术与方法——袁林果2005-2-25 5 Web Resources ? Global Positioning System Overview by Peter H. Dana. http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.ht ml ? THE INTERAGENCY GPS EXECUTIVE BOARD (IGEB). http://www.igeb.gov/ ? GPS Applications Exchange. http://gpshome.ssc.nasa.gov/ ? The International GPS Service (IGS). http://igscb.jpl.nasa.gov/ ? U.S. Naval Observatory (USNO) GPS Operations http://tycho.usno.navy.mil/gps.html ? U.S. Coast Guard Navigation Center http://www.navcen.uscg.gov/ 卫星定位技术与方法——袁林果2005-2-25 6 Global Positioning System (GPS) ?The NAVSTAR Global Positioning System (GPS) is a satellite-based radio-positioning and time-transfer system, designed, financed, deployed and operated by the US Department of Defense. ?However, the system has currently significantly larger number of civilian users as compared to the military users. 4 卫星定位技术与方法——袁林果2005-2-25 7 Global Positioning System (GPS) ? The NAVSTAR Global Positioning System (GPS) program was initiated in 1973 through the combined efforts of the US Army, the US Navy, and the US Air Force. ? The new system, designed as an all-weather, continuous, global radio-navigation system was developed to replace the old satellite navigation system, TRANSIT, which was not capable of providing continuous navigation data in real time on a global basis. 卫星定位技术与方法——袁林果2005-2-25 8 TRANSIT System z Researchers at Johns Hopkins observed Sputnik in 1957. z Noted that the Doppler shift provided closest approach to earth. z Developed a satellite system that achieved accurate positioning z Called TRANSIT and provided basic ideas behind GPS 5 卫星定位技术与方法——袁林果2005-2-25 9 ? Suitable for all classes of platform: aircraft, ship, land-based and space (missiles and satellites), ? Able to handle a wide variety of dynamics, ? Real-time positioning, velocity and time determination capability to an appropriate accuracy, ? The positioning results were to be available on a single global geodetic datum, ? Highest accuracy to be restricted to a certain class of user, ? Resistant to jamming (intentional and unintentional), ? Redundancy provisions to ensure the survivability of the system, GPS – Objectives 1/2 卫星定位技术与方法——袁林果2005-2-25 10 ? Passive positioning system that does not require the transmission of signals from the user to the satellite(s), ? Able to provide the service to an unlimited number of users, ? World-wide coverage ? Low cost, low power, therefore as much complexity as possible should be built into the satellite segment, and ? Total replacement of the Transit 1 satellite and other terrestrial navaid systems. GPS – Objectives 2/2 6 Development of Basic Navigation Satellite Concept 1964-1967 ? SYSTEMATIC STUDY OF EVERY WILD IDEA IMAGINABLE ? CONVERGED ON “PSEUDORANGING” IN 1967 ? MAJOR STUDY CONTRACTS LET IN 1968 TO TUNE THE CONCEPT 卫星定位技术与方法——袁林果2005-2-25 12 The mission of this Program is to: 1. Drop 5 bombs in the same hole, and 2. Build a cheap set that navigates (<$10,000), and don’t you forget it! Motto Adopted by the Joint Program Office on GPS Program 7 卫星定位技术与方法——袁林果2005-2-25 13 Major Issues Identified in 1968 Studies ? CHOICE OF CARRIER FREQUENCY ?L-Band ? C-Band should be studied ? DESIGN OF SIGNAL STRUCTURE ? Military and civilian use included ? ORBIT/CONSTELLATION SELECTION 卫星定位技术与方法——袁林果2005-2-25 14 ? EXPANDED TRANSIT ? Insisted on worldwide overage ? 153 satellites in 400 mile polar orbits ? Transit carrier frequency ? EXPANDED TIMATION ? Initially only a Time Transfer System ? Insisted on worldwide coverage ? Expanded concept to intermediate altitude circular orbit constellation of 30 to 40 satellites Managed Concept Debates 1969-1972 8 卫星定位技术与方法——袁林果2005-2-25 15 Convergence on Final System 1973-1974 ? SWITCHED CONCEPT TO 12-HOUR CIRCULAR ORBITS ? 3 planes, 8 satellites each ?i = 63° ? RETAINED DIRECT-SHIFT KEYED SPREAD SPECTRUM PN SEQUENCE ? DUAL FREQUENCY SIGNAL ON L-BAND ? PICKED INITIAL DEPLOYMENT OF 4+2 ‘BLOCK I” SATELLITES 卫星定位技术与方法——袁林果2005-2-25 16 ? BLOCK I SATELLITE CONTRACTS WITH ROCKWELL INTERNATIONAL ? 6 satellites followed by 6 more ? All satellite performance projections achieved. 3dB more transmitted power then required ? Exceptional (1x ) on-orbit Rubidium clock performance achieved. PHASE I DESIGN 1974-1980 10 -13 ? DETAILS OF SIGNAL STRUCTURE & NAV MESSAGE DEFINED ? C/A code designed with civil sector in mind ? “P-Code” designed by Magnavox ? Navigation message identical on both signals 9 卫星定位技术与方法——袁林果2005-2-25 17 ? BLOCK II SATELLITES ? Rockwell International ? Selective Availability and Anti-Spoof (Y-Code) Implemented ? Constellation downsized to 21 satellites (6 planes) ? Nav message slightly modified ? OPERATIONAL CONTROL SEGMENT ? Monitors at Ascension, Diego Garcia, Guam, Hawaii, and Colorado Springs ? 24-satellite ephemeris (orbit) determination PHASE II DESIGN 1981-1989 ? PHASE II/PHASE III USER EQUIPMENT ? Rockwell Collins, Magnavox and Teledyne Systems ? Rockwell Collins and Magnavox ? Rockwell Collins 卫星定位技术与方法——袁林果2005-2-25 18 GPS Segments 10 卫星定位技术与方法——袁林果2005-2-25 19 Constellation The complete GPS system consists of 24 operational satellites and provides 24-hour, all-weather navigation and surveying capability worldwide. A major milestone in the development of GPS was on 8 December 1993. ? Initial Operational Capability (IOC), 24 satellites (Blocks I, II, IIA) were successfully operating. ? Full Operational Capability (FOC) , 24 satellites of the Block II and IIA types become operational. 卫星定位技术与方法——袁林果2005-2-25 20 GPS Nominal Orbit Planes 11 卫星定位技术与方法——袁林果2005-2-25 21 GPS Constellation ? Block I (not operational) ? Block II/IIA/IIR ? Currently (as of January 5, 2004) - 29 satellites Block II/IIA/IIR (recent launches, 01/29/03, 03/31/03, 12/21/03) -AS 1 /SA capability (to limit the access to the system by unauthorized users) - multiple clocks onboard 1 The process of encrypting the P-code by modulo-2 addition of the P-code and a secret encryption W-code. The resulting code is called the Y-code. AS prevents an encryption-keyed GPS receiver from being “spoofed” by a bogus, enemy-generated GPS P-code signal. Y-code is not available to the civilian users. 2 The Department of Defense policy and procedure of denying to most non-military GPS users the full accuracy of the system. SA is achieved by dithering the satellite clock and degrading the navigation message ephemeris. Turned to zero on May 2, 2000. 卫星定位技术与方法——袁林果2005-2-25 22 GPS Constellation Block I ? vehicle numbers (SVN) 1 through 11 ? launched between 1978 and 1985 ? concept validation satellites ? developed by Rockwell International ? circular orbits ? inclination 63 deg ? one Cesium and two Rubidium clocks ? design life of 5 years (majority performed well beyond their life expectancy) 12 卫星定位技术与方法——袁林果2005-2-25 23 GPS Constellation Block II ? vehicle numbers (SVN) 13 through 21 ? launched between 1989 and 1990 ? full scale operational satellites ? developed by Rockwell International ? nearly circular orbits ? inclination 55 deg ? two Cesium and two Rubidium clocks ? design life of 7.3 years ? AS/SA capabilities 卫星定位技术与方法——袁林果2005-2-25 24 GPS Constellation Block IIA ? vehicle numbers (SVN) 22 through 40 ? launched since 1990 (18 out of 19) ? second series of operational satellites ? developed by Rockwell International ? nearly circular orbits ? inclination 55 deg ? two Cesium and two Rubidium clocks ? design life of 7.3 years ? AS/SA capabilities 13 卫星定位技术与方法——袁林果2005-2-25 25 GPS Constellation Block IIR ? vehicle numbers (SVN) 41 through 62 ? total of 10 (1 unsuccessful) as of January 2004 ? operational replenishment satellites ? developed by Lockheed Martin ? nearly circular orbits ? inclination 55 deg ? one Cesium and two Rubidium clocks ? design life of 7.8 years ? AS/SA capabilities 卫星定位技术与方法——袁林果2005-2-25 26 GPS Constellation Block IIF ? to be launched from 2007 onwards ? operational follow on satellites ? nearly circular orbits ? inclination 55 deg ? design life of 10 years ? will carry an inertial navigation system ? ? will have an augmented signal structure (third frequency) as of 2005 14 卫星定位技术与方法——袁林果2005-2-25 27 GPS Constellation Block III In November 2000, Lockheed Martin and Boeing were each awarded a $16-million, 12-month study contract by the Air Force to conceptualize the next generation GPS satellite, which will be known as GPS Block-3. First launch expected in 2030 and beyond. 卫星定位技术与方法——袁林果2005-2-25 28 ftp://ty cho . usno.nav y .mil/pub /gp s /gpsb2.txt Current GPS Constellation LAUNCH LAUNCH FREQ ORDER PRN SVN DATE STD PLANE --------------------------------------------------------------- ^II-1 14 14 FEB 89 Cs E1 II-2 02 13 10 JUN 89 Cs B3 ^ II-3 16 16 18 AUG 89 Cs E5 ^ II-4 19 19 21 OCT 89 Cs A4 II-5 17 17 11 DEC 89 Cs D3 ^II-6 18 24 JAN 90 Cs F3 *II-7 20 26 MAR 90 II-8 21 21 02 AUG 90 Cs E2 II-9 15 15 01 OCT 90 Cs D2 IIA-10 23 23 26 NOV 90 Cs E4 IIA-11 24 24 04 JUL 91 Rb D1 IIA-12 25 25 23 FEB 92 Cs A2 *IIA-13 28 10 APR 92 IIA-14 26 26 07 JUL 92 Rb F2 IIA-15 27 27 09 SEP 92 Cs A3 IIA-16 01 32 22 NOV 92 Cs F1 IIA-17 29 29 18 DEC 92 Rb F4 IIA-18 22 22 03 FEB 93 Rb B1 LAUNCH LAUNCH FREQ ORDER PRN SVN DATE STD PLANE --------------------------------------------------------------- IIA-19 31 31 30 MAR 93 Cs C3 IIA-20 07 37 13 MAY 93 Rb C4 IIA-21 09 39 26 JUN 93 Cs A1 IIA-22 05 35 30 AUG 93 Cs B4 IIA-23 04 34 26 OCT 93 Rb D4 IIA-24 06 36 10 MAR 94 Cs C1 IIA-25 03 33 28 MAR 96 Cs C2 IIA-26 10 40 16 JUL 96 Cs E3 IIA-27 30 30 12 SEP 96 Cs B2 IIA-28 08 38 06 NOV 97 Rb A5 **IIR-1 42 17 JAN 97 IIR-2 13 43 23 JUL 97 Rb F5 IIR-3 11 46 07 OCT 99 Rb D2 IIR-4 20 51 11 MAY 00 Rb E1 IIR-5 28 44 10 JUL 00 Rb B5 IIR-6 14 41 10 NOV 00 Rb F1 IIR-7 18 54 30 JAN 01 Rb E4 IIR-8 16 56 29 JAN 03 Rb B1 IIR-9 21 45 31 MAR 03 Rb D3 IIR-10 22 47 21 DEC 03 Rb E2 IIR-11 19 59 20 MAR 04 Rb C3 IIR-12 23 60 23 JUN 04 Rb F4 IIR-13 02 61 06 NOV 04 Rb D7 * Satellite is no longer in service. ** Unsuccessful launch. TOTAL: 28 as of January 6, 2003 15 卫星定位技术与方法——袁林果2005-2-25 29 卫星定位技术与方法——袁林果2005-2-25 30 BLOCK I BLOCK II/IIA 16 卫星定位技术与方法——袁林果2005-2-25 31 BLOCK IIF BLOCK IIR 卫星定位技术与方法——袁林果2005-2-25 32 Control Segment ? The Control Segment consists of a system of tracking stations located around the world. ? The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute precise orbital data (ephemeris) and SV clock corrections for each satellite. The Master Control station uploads ephemeris and clock data to the SVs. The SVs then send subsets of the orbital ephemeris data to GPS receivers over radio signals. 17 卫星定位技术与方法——袁林果2005-2-25 33 GPS Master Control and Monitor Network 卫星定位技术与方法——袁林果2005-2-25 34 User Segment The user requires a GPS receiver in order to receive the transmissions from the satellites. The GPS receiver calculates the location based on signals from the satellites. The user does not transmit anything to the satellites and therefore the satellites don't know the user is there. The only data the satellites receive is from the Master Control Station in Colorado. The users consist of both the military and civilians. 18 卫星定位技术与方法——袁林果2005-2-25 35 Application ? cadastral surveying ? geodetic network densification ? high precision aircraft positioning ? monitoring deformation ? photograrnmetry without ground control ? active control stations ? hydrographic surveys ? navigation on land ? navigation on seas ? navigation in the air ? navigation in space ? harbor navigation ? navigation in rivers ? navigation of recreational vehicles ? high precision kinematic surveys on the ground ? guidance of robots and other machines Surveying and PositioningNavigation 卫星定位技术与方法——袁林果2005-2-25 36 Services Precise Positioning Service - PPS(P-code) Standard Positioning Service - SPS(C/A code) 340 nanoseconds200 nanosecondstime transfer 156 meters27.7 metersvertical plane 100 meters22 metershorizontal plane SPS (95%)PPS (95%)Accuracy in: 19 卫星定位技术与方法——袁林果2005-2-25 37 Denial of accuracy and access Two techniques are known for denying civilian users of the system: ? Selective Availability (SA) ? Anti-spoofing (A-S) 卫星定位技术与方法——袁林果2005-2-25 38 Selective Availability (SA) ?Dithering the satellite clock ( -process) When pseudoranges are differenced between two receivers, the dithering effect is eliminated. ?Manipulating the ephemerides ( -process) The orbital errors cause pseudorange errors with similar characteristics. Thus, these errors are highly reduced when psuedoranges are differenced between two receivers. ?SA had been in force since March 25, 1990, and was turned off on May 2, 2000 at about 4:00 Universal Time (UT). δ ε 20 卫星定位技术与方法——袁林果2005-2-25 39 GPS Fluctuations Over Time on May 2, 2000 This is a plot of GPS navigational errors through the SA transition prepared by Rob Conley of Overlook Systems for the GPS Support Center in Colorado Springs, Colorado. The GPS errors can be seen diminishing significantly around 0405 UTC (shortly after midnight EDT). The data indicates a circular error of only 2.8 meters and a spherical error of 4.6 meters during the first few hours of SA-free operation. The data was measured using a Trimble SV6 receiver. 卫星定位技术与方法——袁林果2005-2-25 40 GPS Accuracy Before and After SA Removal The images compare the accuracy of GPS with and without selective availability (SA). Each plot shows the positional scatter of 24 hours of data (0000 to 2359 UTC) taken at one of the Continuously Operating Reference Stations (CORS) operated by the NCAD Corp. at Erlanger, Kentucky. On May 2, 2000, SA was set to zero. The plots show that SA causes 95% of the points to fall within a radius of 45.0 meters. Without SA, 95% of the points fall within a radius of 6.3 meters. May 1, 2000 May 3, 2000 21 卫星定位技术与方法——袁林果2005-2-25 41 New denial developments Although the accuracy for stand-alone receivers if improved by a factor of ten after SA was turned off, it must be kept in mind that despite turning off SA military advantages are ensured by new developments. One of these developments is Selective Denial (SD) which will deny access to the GPS signal for unauthorized users in regions of interest by ground-based jammers. 卫星定位技术与方法——袁林果2005-2-25 42 Anti-spoofing (A-S) A-S is accomplished by the modulo 2 sum of the P- code and an encrypting W-code. The resulting code is denoted as the Y-code. Thus, when A-S is active, the P- code on the L1 and the L2 carrier is replaced by the unknown Y-code. Note that A-S is either on or off. The future signal structure will provide the C/A-code on both the L1 and the L2 carrier. Instead of the Y-code, new military split-spectrum signal, denoted as M-code, will be introduced. This feature will make A-S superfluous. 22 卫星定位技术与方法——袁林果2005-2-25 43 Other global positioning systems z GLONASS (Russia) z Galileo (Europe) z Beiduo (China) 卫星定位技术与方法——袁林果2005-2-25 44 Assignment 1. Please read provided materials. 2. Give a brief description (constellation, frequency, time, accuracy, service, application, etc.) for the four global positioning systems: GPS (USA), Galileo (Europe), Beiduo (China), and GLONASS (Russia) 3. Reference systems? 23 卫星定位技术与方法——袁林果2005-2-25 45 Coordinate systems Questions to ponder ? Why do we need a coordinate system and a time system ? What properties should it have ? How were coordinates defined before space based geodetic systems were available ? How does this type of system relate to space based systems? ? What is needed to define a coordinate system and how are they “realized” (i.e. implemented) ? What is needed to define a time system and how are they “realized” (i.e. implemented)