GPS-A Full Description

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Global Positioning System(GPS)

An easy to usetechnology for everyone

SATELLITE COMMUNICATION


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CONTENTS

Introduction to GPS

Preface to Satellite

Important features of Satellite

Launching a Satellite

Orbits Latitude & Longitude

History of GPS

Basic principle

Working Segments of GPS

Advantages

Applications.

Bibliography


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What is GPS ?

A very precise positioning system

Satellite Based Navigation System

Constellation of 24 satellites.

Developed and maintained by the US

Department of Defense (DOD).

To determine location,time & speed.


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A Preface to SATELLITE

Example- Sputnik 1 :

the first satellite-launchedby Soviet Union in 1957.

is an artificial satellite which revolved around the Earth in an elliptical

orbit in Low Earth Orbit(LEO). used to broadcast radio signals.

Example-Moon :

Is a natural satellite that revolves around the earth in Lunar orbit.

an object which revolves aroundanother reference large body placed

in an orbitinto space.
http://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Orbit


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Some imp. features of Satellite

Weight can vary from 1 kg. to a few thousands of kg. Can operate at temp. ranges from -150C to 150C.

It requires fuel(like Hydrazine-N2H4 or N2O4) to run various

stagesand functions performed in satellite :-

For alligning a satellite to point to a specific location.

For maintaining satellite to remain in its orbit.

Amount of fuel contained also determines the lifespan of satellite.

It also requires power to run its electronic equipments obtainedfrom solar panels or backup batteries.

A minimal fuel is left so as to degrade the satellite to become

space debris or deteriorated.


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Launching a satellite

The first stageof the launch vehicle contains

the rockets and fuel that are needed to lift the

satellite. As satellite is lifted,first stage falls.

The second stagecontains smaller rockets that

ignite after the first stage is finished.

Used to send satellite to the space and burstup in earths atmosphere.

Launched with the help of rockets which go under differentstages to make the satellite suspended to its orbit.

The upper stage is enclosed in a metal shield, called fairing.

The satellite separates from the upper stage & moves to transfer orbit.

Once the satellite reaches its desired orbital height,it unfurls its solar

panels and communication antennas.


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Launched by ISRO On 4th April 2014 from the Satish Dhawan

Space Center,about 50 miles north of Chennai.

Weighed 1,432 kg at an altitude of 20,610 km. Geosynchronous

orbit.

Designed for a 10-year lifetime.

Five more Indian navigation spacecraft are scheduled for launch by

mid-2015.


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Orbits

An orbitis the

gravitationally curved pathof an object around a point

in space.

Orbits ofplanetsaretypically elliptical.

Types of ORBITS -:

LEO MEO

GEO/GSO

HEO
http://en.wikipedia.org/wiki/Planetshttp://en.wikipedia.org/wiki/Ellipticalhttp://en.wikipedia.org/wiki/Ellipticalhttp://en.wikipedia.org/wiki/Planets


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LEO(LOWER EARTH ORBI T)

Closest to earth.

Extends upto an altitude of 160-2000 Km.

Orbiting period is 90 min.

Orbital speed is about 28,000-30,000 Km./h

Have less lifespan-approx. 5 yrs.

Advantages-

Access to visit Hubble Space Telescope & International Space Station.

Only way to go up and do experiments,testing & repairing of satellites.

High resolution pictures.

Ozone layer & other atmospheric disturbances monitoring.

Disadvantages-

Atmospheric Drag.

Less Dwell Time.


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Extends upto an altitude of 2000-35,786 Km.(optimum

value-20,000 km.) Orbiting period is12 hrs.

Orbital speed is about 18,000Km./h

Have an average lifespan-approx. 10 yrs. GPS satellites mostly orbits in MEO.

Advantages-

Used for navigation, communicationand space

environmentscience.

Signal time delay is less.

MEO(MEDIUM EARTH ORBIT)
http://en.wikipedia.org/wiki/Navigationhttp://en.wikipedia.org/wiki/Communicationhttp://en.wikipedia.org/wiki/Space_environmenthttp://en.wikipedia.org/wiki/Space_environmenthttp://en.wikipedia.org/wiki/Space_environmenthttp://en.wikipedia.org/wiki/Space_environmenthttp://en.wikipedia.org/wiki/Communicationhttp://en.wikipedia.org/wiki/Navigation


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Extends upto an altitude of 50,000 km. to somelakhs of km.

Above this orbit is the-graveyard Orbit.

Orbiting period is some days.Orbital speed is about 3,000-5000 Km/h

Example:-

Moon-have an altitude of 3,85,000 km.

Orbital speed is 3,600 km/h and takes 25 days

to complete its orbit around the Earth.

HEO(H IGH EARTH ORBIT)


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LATITUDE AND LONGITUDE

Latitude - is the angular distance, in degrees,minutes, and seconds of a point north or south

of the Equator. Lines of latitude are often

referred to as parallels.

Longitude- is the angular distance, in degrees,

minutes, and seconds, of a point east or west of

the Prime (Greenwich) Meridian. Lines of

longitude are often referred to as meridians.

Altitude-is the distance of an object

measured w.r.t ground or sea level usually in

vertical direction.


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History of GPS

Ivan A. Getting Roger L. Easton Bradford Parkinson

GPS was initially created for the United States Air Force by the Raytheon Company.

In 1967, the U.S. Navy launched TRANSIT, the first satellite navigational system,

which was used to help guide the Navys submarines-missiles.

1974, the first atomic clocks were put into orbit.

By 1978, the U.S. military had launched the first four GPS satellites.

Until 1983, GPS technology was available for U.S. military use only.In 1983,due to a tragedy with Korean Air Lines Flight 007 accident, President

Ronald Reagan (U.S)issued a directivethat when GPS technology was operational, it

would be free and available to the world.

On Feb. 14, 1989, the first modern satellite,USA-35 was launched.

By July 17, 1995, the global positioning system was complete.
http://www.fas.org/spp/military/program/nav/transit.htmhttp://support.radioshack.com/support_tutorials/gps/gps_tmline.htmhttp://www.america.gov/st/washfile-english/2006/February/20060203125928lcnirellep0.5061609.htmlhttp://www.america.gov/st/washfile-english/2006/February/20060203125928lcnirellep0.5061609.htmlhttp://support.radioshack.com/support_tutorials/gps/gps_tmline.htmhttp://en.wikipedia.org/wiki/USA-35http://en.wikipedia.org/wiki/USA-35http://support.radioshack.com/support_tutorials/gps/gps_tmline.htmhttp://support.radioshack.com/support_tutorials/gps/gps_tmline.htmhttp://en.wikipedia.org/wiki/USA-35http://en.wikipedia.org/wiki/USA-35http://en.wikipedia.org/wiki/USA-35http://en.wikipedia.org/wiki/USA-35http://support.radioshack.com/support_tutorials/gps/gps_tmline.htmhttp://www.america.gov/st/washfile-english/2006/February/20060203125928lcnirellep0.5061609.htmlhttp://www.america.gov/st/washfile-english/2006/February/20060203125928lcnirellep0.5061609.htmlhttp://support.radioshack.com/support_tutorials/gps/gps_tmline.htmhttp://www.fas.org/spp/military/program/nav/transit.htm


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Principle of GPS

TRILATERATION :-

Process to determine your position on a map knowing the

precise distance from three different landmarks using a pair of

compasses. Where the three circles centered on each of the

landmarks overlap,gives you,your location.

In GPS, the calculations are carried out in three-

dimensions with an imaginary set of 3D compasses so that

your location is where three spheres of radius given by the

distance to each of three satellites overlap.

4 satellites gives accuracy.


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How GPS Works

Uses measurements from 4+ satellitesDistance = travel time x speed of light

Source:Trimble


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Each satellite knows its

position and its distance

from the center of the earth.

Each satellite constantly

broadcasts this information.

With this information andthe calculated distance, the

receiver calculates its

position.

Just knowing the distanceto one satellite doesnt

provide enough

information.


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When the receiver

knows its distance from

only one satellite, itslocation could be

anywhere on the earths

surface that is an equaldistance from the

satellite.

Represented by thecircle in the illustration.

The receiver must have

additional information.


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With signals from two

satellites, the receiver can

narrow down its location tojust two points on the earths

surface.

Where the two circles

intersect.


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Knowing its distance

from three satellites, the

receiver can determine itslocation because there is

only two possible

combinations and one of

them is out in space.

In this example, the

receiver is located at b.

The more satellite that areused, the greater the

potential accuracy of the

position location.


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Segments of GPS

1. Space SegmentA constel lation of 24 satel l i tes

2. Control SegmentA network of earth-based faci l i ties

Source:Trimble

1. Users SegmentGround, Sky and Marine.


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1.Space Segment

The current GPS configuration consists ofa constellation of 24 satellites(with 6

spares)in high orbits around the Earth.

Extends at an altitude of about 20,000 km.

Has an orbital speed of about 14,000 km/hr& orbital period is roughly 12 hrs.

The orbits are designed so that there are

always 6 satellites in view,from most

places on the earth.

Powered by solar cells, the satellites continuously

orient themselves to point their solar panels toward

the sun and their antenna toward the earth.


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2.Control Segment

The CS consists of 3 entities:

Master Control Station

Monitor Stations

Ground Antennas

1. Master Control Station The master control station, located at Falcon Air Force Base in

Colorado Springs, Colorado, is responsible for overall management of

the remote monitoring and transmission sites.

Provide commands and control of the GPS constellation. It generates and uploads navigation messages and ensures the health

and accuracy of the satellite constellation.

It receives navigation information from the monitor stations, utilizes

this information to compute the precise locations of the GPS satellites in

space, and then uploads this data to the satellites.


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2. Monitor Stations

Monitor stations track the GPS satellites as they pass overhead and

channel their observations back to the master control station. Monitor stations collect atmospheric data, range/carrier

measurements, and navigation signals.

The sites utilize sophisticated GPS receivers and are operated by

the MCS.

There are 16 monitoring stations located throughout the world,

including six from the Air Force and 10 from the National

Geospatial-Intelligence Agency (NGA).

3. Ground Antennas

Ground antennas monitor and track the satellites from horizon to

horizon.

They also transmit correction information to individual satellites.


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3.User Segment

GPS receivers are generally composed of an antenna, tuned to

the frequencies transmitted by the satellites.

They can also include a display for showing location and

speed information to the user.

A receiver is often described by its number of channels this

signifies how many satellites it can monitor simultaneously.

Some Common Receivers are -:


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MAP for location of Control Stations


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Advantages of GPS

Free of costEasy to use

Reliable to much extent

Unlimited Users Capacity

Operates in all Weather conditionsComplete coverage of Globe

Updated regularly

Compact-Mobile phones/Watches

Full time access

Determination of exact location,distance & speed.Gives you inf. About Latitude & Longitude.

Allows to search for nearby Ammenities.

Determination of traffic,weather conditions.

Keep track of your friends or targets location.


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Applications of GPS

ROAD APPLICATIONS

Used to determine location,speed,traffic and distance to destination. Used to search nearby Ammenities like malls,restaurants,theatres etc.

Sources include-Mobiles,Laptos,GPS mount for automobiles.

SPACE APPLICATIONS

Weather monitoring, Launch Vehicle tracking, Disaster Alerts,Space Shuttle nav.

Keep track of other space elements like space debris,asteroids,etc.

RAIL APPLICATIONS

To maintain smooth flow of traffic.

Prevent collisions by precise knowledge of other trains locations.

MILITARY: GPS systems are installed with fighters, bombers, tankers, helicopters,ships, submarines, tanks, jeeps and soldiers to combat various attacks.

AVIATION APPLICATIONS:GPS provides position determination for all phases

of flight from departure, en route, and arrival, to airport surface navigation.

AGRICULTURE:farm planning, field mapping, soil sampling, tractor guidance,

crop scouting, variable rate applications, and yield mapping.


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Bibliography

www.wikipedia.org

www.youtube.com

www.astronomy.ohio-state.eduwww.mio.com

www.cfa.harvard.edu

www.gpspassion.comwww.lockheedmartin.co.in

http://gps.about.com/
http://www.wikipedia.org/http://www.youtube.com/http://www.astronomy.ohio-state.edu/http://www.mio.com/http://www.cfa.harvard.edu/http://www.gpspassion.com/http://www.lockheedmartin.co.in/http://gps.about.com/http://gps.about.com/http://www.lockheedmartin.co.in/http://www.gpspassion.com/http://www.cfa.harvard.edu/http://www.mio.com/http://www.astronomy.ohio-state.edu/http://www.astronomy.ohio-state.edu/http://www.astronomy.ohio-state.edu/http://www.youtube.com/http://www.wikipedia.org/


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GPS-A Full Description

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