GPS
GPS - Global Positioning System.
GPS is a space based satellite system that provides the information about exact position on the Earth, anywhere and anytime in all weather conditions.
It is maintained by the US government and is freely accessible by anyone having a GPS receiver.
GPS was developed by the Department of Defense (DoD) and it consists of 24 satellites.
It is maintained by the US government and is freely accessible by anyone having a GPS receiver.
GPS was developed by the Department of Defense (DoD) and it consists of 24 satellites.
BASIC CONCEPT:
A GPS receiver calculates its position by timing the signals sent by the GPS satellites above the Earth. Each satellite message contains
- Time of the transmitted message
- Satellite position at the time of message transmission.
Using this message, the receiver determines the transit time of each message and computes the distance of each satellite in the speed of light.
From this information, the location of the receiver was determined.
Then the location is displayed using a moving map display or latitude and longitude.
Elevation, altitude, direction and speed information may also be included.
From this information, the location of the receiver was determined.
Then the location is displayed using a moving map display or latitude and longitude.
Elevation, altitude, direction and speed information may also be included.
STRUCTURE:
GPS consists of 3 segments:
- Space segment
- Control segment
- User segment
SPACE SEGMENT:
Space segment composed of orbiting GPS satellite or Space Vehicles (SVs) which is 24 in number having six orbital planes with 4 satellites each.
The orbital planes are inclined at 55°. Orbital period is one half a sidereal days i.e., 11 hours & 58 minutes.
Hence each SV makes 2 complete orbits each sidereal day.
There are about 32 satellites in GPS constellation by Dec 2012.
The additional satellites are used to improve the accuracy of the GPS receiver.
The orbital planes are inclined at 55°. Orbital period is one half a sidereal days i.e., 11 hours & 58 minutes.
Hence each SV makes 2 complete orbits each sidereal day.
There are about 32 satellites in GPS constellation by Dec 2012.
The additional satellites are used to improve the accuracy of the GPS receiver.
CONTROL SEGMENT:
The control segment is composed of
- a master control station (MCS),
- an alternate master control station,
- four dedicated ground antennas and
- Six dedicated monitor stations.
GPS control segment consists of monitor stations located around the world.
The monitor station receives the signal from the SV and computes the orbital data and clock correction for each satellite sends it to SVs within a nano seconds.
The monitor station receives the signal from the SV and computes the orbital data and clock correction for each satellite sends it to SVs within a nano seconds.
USER SEGMENT:
User segment composed of receiver that are now available in variety of formats which can be integrated into cars, phones, watches, etc.
It consists of an antenna that can be tuned to the transmitting frequency of satellite, receiver processor and highly stable clock.
It consists of displays for giving speed and location information to the user.
Receiver is usually described by its number of channels which indicates the number of satellites that it can monitor simultaneously.
It consists of an antenna that can be tuned to the transmitting frequency of satellite, receiver processor and highly stable clock.
It consists of displays for giving speed and location information to the user.
Receiver is usually described by its number of channels which indicates the number of satellites that it can monitor simultaneously.
APPLICATIONS:
Civilian:
Many civilian applications use one or more GPS components.
Some of the civil applications are astronomy, automated vehicle, cartography, cellular telephony, clock synchronization, disaster relief, GPS for mining, navigation, Robotics, Surveying, Tectonics, Telematics, etc.
Military:
It is used for navigation, Target tracking, Missile & Projectile guidance, Search & Rescue, Reconnaissance.
Many civilian applications use one or more GPS components.
Some of the civil applications are astronomy, automated vehicle, cartography, cellular telephony, clock synchronization, disaster relief, GPS for mining, navigation, Robotics, Surveying, Tectonics, Telematics, etc.
Military:
It is used for navigation, Target tracking, Missile & Projectile guidance, Search & Rescue, Reconnaissance.
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