Post on 20-Aug-2015
transcript
INSTITUTE OF TECHNOLOGY & MANAGEMENT
PRESENTATION ON
GPS
PREPARED BY : KUNAL PRAKASH MISHRA
ECE 4’th YR.
Introduction Working Different segments of GPS Primary function of GPS GPS position location principle PSEUDO RANDOM NOISE code Equations involved Sources of signal interference GPS receiver DGPS Applications of GPS
CONTENTS
INTRODUCTION
It is global positioning system used for position location & navigation.
It is a network of 24 NAVSTAR satellites orbiting around earth at an altitude of approx. 20200 kms.
In this system satellites are placed in MEO
It consists of satellites ,receivers & ground control systems.
It is operated on L –band frequency(1-2GHz).
A GPS works in any weather condition
contd… It provides a direct readout of the present
position of a GPS receiver with a typical accuracy of 30 m.
The orbital period of a satellite is approx. one-half a sidereal day (11hr 58 min)
LORAN is also used for position location
There are three segments of a GPS & they are:
1.Control segment
2.Space segment
3.User segment
CONTROL SEGMENT
A control segment is composed of :
1.A master control station
2.Four dedicated ground stations
3.Six dedicated monitor stations
Control Segment
Space Segment
User Segment
Three Segments of the GPSThree Segments of the GPS
Monitor Stations
GroundAntennas
Master Station
Kwajalein Atoll
US Space Command
Control SegmentControl Segment
Hawaii
Ascension Is.
Diego Garcia
Cape Canaveral
Ground AntennaMaster Control Station Monitor Station
Military. Search and rescue. Disaster relief. Surveying. Marine, aeronautical and terrestrial navigation. Remote controlled vehicle and robot guidance. Satellite positioning and tracking. Shipping. Geographic Information Systems (GIS). Recreation.
User Segment
Position and coordinates.
The distance and direction between any two waypoints, or a position and a waypoint.
Travel progress reports.
Accurate time measurement.
Four Primary Functions of GPS
Position is Based on TimePosition is Based on Time
T + 3
Then distance between satellite and receiver = “3 times the speed of light”
T
Radio waves travel at the speed of light. If GPS signal leaves satellite at time “T”…
…and is picked up by the receiver at time “T + 3.”
Sources of GPS ErrorStandard 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 User error: Up to a kilometer or more
Errors are cumulative
Sources of Signal InterferenceSources of Signal Interference
Earth’s Atmosphere
Solid Structures
Metal Electro-magnetic Fields
DGPS Site
x+30, y+60
x+5, y-3
True coordinates = x+0, y+0
Correction = x-5, y+3
DGPS correction = x+(30-5) and y+(60+3)
True coordinates = x+25, y+63
x-5, y+3
Real Time Differential GPSReal Time Differential GPS
DGPS ReceiverReceiver
A visual example of the GPS constellation in motion with the Earth rotating. Notice how the number of satellites in view from a given point on the Earth's
surface, in this example at 45°N, changes with time.
APPLICATIONGPS has become a widely used & useful tool for commerce, scientific uses , tracking & surveillance.
1.Surveying
2.map-making
3.Navigation
4.Cellular telephony
5.Tectonics( fault motion measurement in earthquakes)
6.Geofencing (vehicle ,person tracking systems)
7. Military