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GPS
What is GPS?What is GPS?
GPS is a space based all weather radio navigation system.
GPS
Provides
Position (geographic), Velocity & Time (PVT) Quickly, Economically And
Precisely 24 hours a day, anywhere in the world under the sky
Components of GPSComponents of GPS
Space segmentSpace segment
Control segmentControl segment
User segmentUser segment
Salient stepsSalient stepsSalient stepsSalient steps
1.1. The receiver picks up the signals from the The receiver picks up the signals from the
satellites;satellites;
2.2. Uses signal travel time to calculate distance Uses signal travel time to calculate distance to the satellitesto the satellites
3.3. Using Analytical Principle, position of the Using Analytical Principle, position of the receiver gets calculated.receiver gets calculated.
Space segmentSpace segment
24 satellites 24 satellites
Orbit every 12 hours at 20,200 kmsOrbit every 12 hours at 20,200 kms
4 satellites in each of 6 orbital planes4 satellites in each of 6 orbital planes
Transmit a uniquely coded radio signalTransmit a uniquely coded radio signal
Equipped with onboard atomic standardEquipped with onboard atomic standard
What is so special about an 20200 km orbit?
• ‘Orbits’ twice per day
• Large ‘viewable’ area
Positioning With Satellite
• Satellites are reference points to locations on earth (their location are known)
• A location of a point on earth is identified by “triangulation”
• Travel time of each signal is determined• Signals travel at Speed of light• Distance = Travel Time * Speed of Light
Principle of working using GPS Principle of working using GPS
• The basis of GPS technology is precise measurement of time;
• Use of orbiting satellite position to find location of receiver by method of resection
Pseudoranging
d
One-way ranging in GPS* Sattellite clock generates a signal* Receiver clock detects the signal arrival* The two clocks must keep the same time
Travel time: t=d/c (one way)Distance: d=ct
SS11(x(x11,y,y11,z,z11))
SS22(x(x22,y,y22,z,z22))
SS33(x(x33,y,y33,z,z33)) SS44(x(x44,y,y44,z,z44))
GPS Receiver
1 1 = = {(x{(x11-x)-x)22+(y+(y11-y)-y)22+(z+(z11-z)-z)22} + c.} + c.ΔΔtt
2 2 = = {(x{(x22-x)-x)22+(y+(y22-y)-y)22+(z+(z22-z)-z)22} + c.} + c.ΔΔtt
3 3 = = {(x{(x33-x)-x)22+(y+(y33-y)-y)22+(z+(z33-z)-z)22} + c.} + c.ΔΔtt
44 = = {(x{(x44-x)-x)22+(y+(y44-y)-y)22+(z+(z44-z)-z)22} + c.} + c.ΔΔtt
Principle of GPS PositioningPrinciple of GPS Positioning
(X,Y,Z)(X,Y,Z)
Control segmentControl segment
Ground-based monitoring and upload Ground-based monitoring and upload stationsstations
Control orbit and timing informationControl orbit and timing information
USER
It includes all GPS users. User can receive the GPS signals through antenna connected to the receiver and can determine its position on the surface of the earth
User segmentUser segmentUser segmentUser segment
GPS Receivers;GPS Receivers;
Compatible software for Planning, Compatible software for Planning, Downloading and Processing of GPS Downloading and Processing of GPS receiver data;receiver data;
Some Applications of GPS
Some Applications of GPS
Some Applications of GPS
Some Applications of GPS
GPS Receivers (contd.)GPS Receivers (contd.)
NavigationNavigation capable of about 12 capable of about 12
meter accuracy meter accuracy
light-weight, light-weight, cheap!cheap!
navigation navigation applicationsapplications
GPS data processing software
• Real time
• Post-processing
GPS Coordinate system
• World Geodetic System, 1984 (WGS84)
GPS receivers Positioning Techniques
– Absolute
– Relative
• Real Time
• Post-processing
LIMITATIONS
• Ionospheric delay correction is not possible to compute
• Weak signal – not available under canopy or under shed
• Susceptible to interference
GPS is getting popularas a means for collection
of data
GPS DATA
• Reliable
• Accurate
• Real-time
GPS
Can be used in any conceivable situation
Under the sky
Where the exact position of any object or phenomena involved.
Thank You