Chap5 GPS

交通通信网络基础
Transportation communication network
GPS系统定位原理
Triangulating Correct Position
交通通信网络基础
Transportation communication network
GPS系统定位原理
GPS position – 2 satellites
交通通信网络基础
Transportation communication network
GPS的历史
可行性研究始于 1960’s. 1973年美国国防部五角大楼拨款 年美国国防部五角大楼拨款. 1973年美国国防部五角大楼拨款. 1978年发射第一个用于GPS的卫星 年发射第一个用于GPS的卫星. 1978年发射第一个用于GPS的卫星. 1995年 月整个系统开始运营. 1995年4月整个系统开始运营.
交通通信网络基础
TransportBaidu Nhomakorabeation communication network
Sources of GPS Error
Standard Positioning Service (SPS ): Civilian Users Source Amount of Error Satellite clocks: 1.5 to 3.6 meters Orbital errors: < 1 meter Ionosphere: 5.0 to 7.0 meters Troposphere: 0.5 to 0.7 meters Receiver noise: 0.3 to 1.5 meters Multipath: 0.6 to 1.2 meters Selective Availability (see notes) User error: Up to a kilometer or more Errors are cumulative and increased by PDOP.
Transportation communication network
GPS Dilution of Precision and Its Affects On GPS Accuracy
交通通信网络基础
Transportation communication network
地面控制Control Segment
US Space Command
Cape Canaveral Hawaii Kwajalein Atoll Diego Garcia Ascension Is.
Master Control Station 1个主控站
Monitor Station 5个监测站
Ground Antenna 地面注入站
Source: Garmin GPS Guide for Beginners
交通通信网络基础
Transportation communication network
GPS系统定位原理
GPS position – 3 satellites
Source: Garmin GPS Guide for Beginners
交通通信网络基础
Transportation communication network
GPS的四项基本功能
Position and coordinates. The distance and direction between any two waypoints, or a position and a waypoint. Travel progress reports. Accurate time measurement.
交通通信网络基础
Transportation communication network
通过“测时” 而“定位”
Signal leaves satellite at time “T”
T
T+3
Signal is picked up by the receiver at time “T + 3”
Distance between satellite and receiver = “3 times the speed of light”
交通通信网络基础
Transportation communication network
用户设备 User Segment
军事Military. 军事 寻找和救援Search and rescue. 寻找和救援 减灾Disaster relief. 减灾 调查Surveying. 调查 海事、航空、 海事、航空、陆地导航 Marine, aeronautical and terrestrial navigation. 遥控汽车和火箭引导 Remote controlled vehicle and robot guidance. 卫星定位和跟踪Satellite positioning and tracking. 卫星定位和跟踪 海运Shipping. 海运 地理信息系统Geographic Information Systems (GIS). 地理信息系统 休闲娱乐Recreation. 休闲娱乐
交通通信网络基础
Transportation communication network
通过“测时” 而“定位”
Time Difference
Pseudo Random Noise Code
Satellite PRN
Receiver PRN
交通通信网络基础
Transportation communication network
交通通信网络基础
Transportation communication network
空间部分Space Segment
• 24 satellites • Six orbital planes
– Inclined 55o with respect to equator – Orbits separated by 60o
交通通信网络基础
Transportation communication network
GPS系统定位原理
Signals From Two Satellites
交通通信网络基础
Transportation communication network
GPS系统定位原理
Three Satellites (2D Positioning)
* GPS Time is ahead of UTC by approximately 13 seconds
交通通信网络基础
Transportation communication network
GPS系统定位原理
Signal From One Satellite
The receiver is somewhere on this sphere.
Chap.5 全球定位系统及应用
Transportation communication network ---GPS and its application
交通通信网络基础
Transportation communication network
学术资源
• 维基百科
– http://en.wikipedia.org/wiki/Global_Positioning_System
交通通信网络基础
Transportation communication network
Position is Based on Time
Three Dimensional (3D) Positioning
交通通信网络基础
Transportation communication network
Position is Based on Time
交通通信网络基础
Transportation communication network
Sources of Signal Interference
Sources of Signal Interference
Solid Structures
Metal
Electro-magnetic Fields
交通通信网络基础
通过“测时” 而“定位”
What Time is It?
Universal Coordinated Time
Greenwich Mean Time
GPS Time + 13*
Zulu Time
Local Time: AM and PM (adjusted for local time zone) Military Time (local time on a 24 hour clock)
Selective Availability (S/A)
The Defense Department dithered the satellite time message, reducing position accuracy to some GPS users. S/A was designed to prevent America’s enemies from using GPS against us and our allies. In May 2000 the Pentagon reduced S/A to zero meters error. S/A could be reactivated at any time by the Pentagon.
• GPS主页 GPS主页
– http://www.gps.gov/
• GPS介绍 GPS介绍
– http://www.trimble.com/gps/index.shtml
• 学术杂志
– World GPS (free) http://www.gpsworld.com/ – GPS Solutions (SCIE检索) 原 The Journal of Global Navigation Satellite Systems http://www.springerlink.com/content/109380/?p=cc72abb10efd42 c2b46be44fce77a953&pi=0
交通通信网络基础
Transportation communication network
Sources of GPS Error
Receiver Errors are Cumulative!
System and other flaws = < 9 meters
User error = +- 1 km
交通通信网络基础
Transportation communication network
GPS系统介绍
包括24颗有效工作卫星， 包括24颗有效工作卫星，4颗 24颗有效工作卫星 备用卫星， 备用卫星，每科卫星每天运行 2周 提供特殊编码卫星信号便于 GPS接收器接收信号 接收器接收信号, GPS接收器接收信号, 计算位 置，速度和时间 通常需要4 通常需要4颗卫星的信号来计 算三维的位置和接收器的时间 偏差 GPS接收仪测量卫星发送信号 GPS接收仪测量卫星发送信号 时间和地面接收时间
监控站Monitor Stations
交通通信网络基础
Transportation communication network
GPS接收器
• Garmin eTrex – ~$100 • Garmin-12 – ~$150 • Casio GPS wristwatch – ~$300 • The GPS Store
交通通信网络基础
Transportation communication network
GPS系统的三大组分
空间部分 Space Segment
地面控制部分 Control Segment
用户设备 User Segment 地面天线 Ground Antennas
主控站Master Station
• 20,200 km elevation above Earth • Orbital period of 11 hr 55 min • Five to eight satellites visible from any point on Earth
交通通信网络基础
Transportation communication network