global positioning sysstem

8/7/2019 global positioning sysstem

1/40

Presented By-

SANDIP KUMAR PATTANAIK

ROLL NO.---0401101169


2/40

1. Introduction.2. History of GPS3. Components of GPS

4. How does GPS work5. GPS capabilities6. Errors in GPS system.

7. Parts of GPS Network8. Application of GPS system9. Conclusion


3/40

INTRODUCTION

y The Global Positioning System (GPS) is a satellite-basednavigation system made up of a network of 24 satellites

that orbit the Earth and make it possible for people withground receivers to pinpoint their geographic location

y GPS satellites circle the earth twice a day in a veryprecise orbit and transmit signal information to earth.

y GPS satellites orbit around 11000 nautical miles abovethe Earth. They are monitored continuously at the

ground station around the world.


4/40

United States Department of Defense developed thesystem, officially named NAVSTAR GPS (NavigationSignal Timing and Ranging GPS), and the satelliteconstellation is managed by the 50th Space Wing atSchriever Air Force Base. Although the cost ofmaintaining the system is approximately US$400million per year, including the replacement of aging

satellites, GPS is available for free use in civilianapplications as a public good.

In late 2005, the first in a series of next-generationGPS satellites was added to the constellation, offering

several new capabilities. There is also another GPS system in Russia known as

GLONASS which may prove complementary toNAVSTAR


5/40

HISTORY OF GPS

yGPS was first launched in the year 1978.

y The first 10 satellites launched weredevelopmental satellite.

y The launch of 24th satellite was completed in

1994.

y The Third generation satellite, block IIR werelaunched in 1997.

y

The Next generation, Block IIF, is launched inlate 2005.


6/40

VISUAL EXAMPLE OF GPS

y A visual example of the GPS constellation in motion with the Earthrotating. Notice how the number of satellites in view from a givenpoint on the Earth's surface, in this example at 45N, changes with


7/40

Components of the GPS

Space Segment Control Segment User Segment

GPS


8/40


9/40

Space Segment:

y 24 GPS spacevehicles(SVs).

y Satellites orbit theearth in 12 hrs.

y 6 orbital planesinclined at 55 degreeswith the equator.

y Th

is constellationprovides 5 to 8 SVsfrom any point on theearth.


10/40

Paul Lammertsma

equator

orbital plane20,200 km

55

6 planes

Configuration


11/40

Control segment:

y The control segmentcomprises of 5 stations.

y They measure thedistances of the overheadsatellites every 1.5 secondsand send the correcteddata to Master control.

y Here the satellite orbit,clock performance andhealth of the satellite aredetermined anddetermines whether

repositioning is required.y This information is sent to

the three uplink stations


12/40

User Segment:y It consists of receivers that decode the signals from the

satellites.

y The receiver performs following tasks:y Selecting one or more satellites

y Acquiring GPS signals

y Measuring and tracking

y Recovering navigation data


13/40

The Global Positioning System (GPS) is a satellite-basednavigation system made up of a network of 24 satellites

placed into the orbit of earth.

GPS was originally intended for military applications, butlater on the government made the system available for civilianuse.

GPS works in any weather conditions, anywhere in the world,24 hours a day.

There are no subscription fees or setup charges to use GPS.

GPS satellites circle the earth twice a day in a very preciseorbit and transmit signal information to earth.


14/40

United States Department of Defense developed the system,officially named NAVSTAR GPS (Navigation Signal Timing and

Ranging GPS), and the satellite constellation is managed by the

50th Space Wing at Schriever Air Force Base. Although the cost of

maintaining the system is approximately US$400 million per year,

including the replacement of aging satellites, GPS is available forfree use in civilian applications as a public good.

In late 2005, the first in a series of next-generation GPS satellites

was added to the constellation, offering several new capabilities.

There is also another GPS system in Russia known as GLONASS

which may prove complementary to NAVSTAR


15/40

Here are some other interesting facts about the GPSsatellites (also called NAVSTAR, the official U.S.Department of Defense name for GPS):

The first GPS satellite was launched in 1978. A full constellation of 24 satellites was achieved in

1994. Each satellite is built to last about 10 years.Replacements are constantly being built andlaunched into orbit.

A GPS satellite weigh

s approximately 2,000 poundsand is about 17 feet across with the solar panelsextended.

Transmitter power is only 50 watts or less.


16/40

A Ground Trackmap shows how this

scheme covers the Earth.


17/40

Space Segment:

y 24 GPS spacevehicles(SVs).

y Satellites orbit theearth in 12 hrs.

y 6 orbital planesinclined at 55 degreeswith the equator.

y This constellationprovides 5 to 8 SVsfrom any point on theearth.


18/40

Paul Lammertsma

equator

orbital plane20,200 km

55

6 planes

Configuration


19/40

Control segment:

y The control segmentcomprises of 5 stations.

y They measure thedistances of the overheadsatellites every 1.5 secondsand send the corrected

data to Master control.y Here the satellite orbit,

clock performance andhealth of the satellite aredetermined anddetermines whether

repositioning is required.y This information is sent to

the three uplink stations


20/40

User Segment:y It consists of receivers that decode the signals from the

satellites.

y The receiver performs following tasks:y Selecting one or more satellites

y Acquiring GPS signals

y Measuring and tracking

y Recovering navigation data


21/40

User Segment:y There are two services SPS and PPS

y The Standard Positioning Service

Each satellite transmits two l band frequencies L1 &L2 SPS- is position accuracy based on GPS measurements

on single L1 frequency C/A code

C/A ( coarse /acquisition or clear/access) does pseudo

random bi phase modulation on L1 freq


22/40

User Segment:y The Precise Position Service

y PPS is the highest level of dynamic positioning based onthe dual freq P-code

y The P-code is a very long pseudo-random bi phasemodulation on the GPS carrier which does not repeat for267 days

y Only authorized users, this consists of SPS signal plus

th

e P code on L1 and L2 and carrier ph

ase measurementon L2


23/40

The Broadcast

y Satellites broadcast over two reserved frequenciesy L1 frequency, at 1575.42 MHzy

L2 frequency, at 1227.6 MHzy L1 carries a C/A code, which can be identified by

civil receiversy L1 & L2 carry a P code, which can only be identified

by the U.S. military


24/40

GPS Satellite Signal:y L1 freq. (1575.42 MHz) carries the SPS code and the

navigation message.

y

L2 freq. (1227.60 MHz) used to measureionosphere delays by PPS receivers

y 2 binary codes on L1 &L2 by the carrier phase arey The C/A code

y The P code


25/40

How does the GPS work?y Requirements

y Triangulation from satellite

y

Distance measurement th

rough

travel time of radiosignals

y Very accurate timing required

y To measure distance ,the location of the satelliteshould also be known

y Finally delays have to be corrected


26/40

PARTS OF GPS NETWORK

y GPS satellites.

y GPS ground support.

y GPS receivers.

Requirements


27/40

Triangulationy Position is calculated

from distancemeasurement

y Mathematically weneed four satellitesbut three are

sufficient byrejecting theridiculous answer


28/40

Pseudo range

Were exactly here

In two dimensions, this is the ideal situation


29/40

Howitworks

The image cannot be displayed. Your computer may not have enough memory to open the image, or the imagemay have been corrupted. Restart your computer, and then open the file again. If the red x still appears, youmay have to delete the image and then insert it again.

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may havebeen corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete theimage and then insert it again.

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have beencorrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image andthen insert it again.


30/40

Measuring Distancey Distance to a satellite is determined by measuring how

long a radio signal takes to reach us from the satellite

y

Assuming the satellite and receiver clocks are sync.The delay of the code in the receiver multiplied by thespeed of light gives us the distance

Distance = Time delay X Speed of light


31/40

time difference

pseudo-randomcode generated

by GPS receiver

on the ground

pseudo-random

code generatedby GPS satellite

in space

The GPS receiver and satellite generate the same pseudo-random code at

exactly the same time. When the code arrives from the satellite, the time

difference is compared to the same code generated by the receiver. Thisdifference is multiplied by the speed of light (186,000 miles per second) to

determine the distance to the satellite.


32/40

Getting Perfect timingy If the clocks are perfect sync the satellite range will

intersect at a single point.

y

But imperfect if the four satellite will not intersect atthe same point.

y The receiver looks for a common correction that willmake all the satellite intersect at the same point


33/40

TypicalGPS Applicationsy Location - determining a basic position

y

Navigation - getting from one location to anoth

er

y Tracking - monitoring the movement of people andthings.

y Mapping - creating maps of the world

y Timing - bringing precise timing to the world


34/40


35/40

Sublocations can have multiple

scales

Country level State level

City level

Campus level


36/40

Errors

y Other objects exert gravitational force on each satellite

(e.g. sun, moon)y Effect of gravity is non-uniform during orbit.

y Radiation pressure (due to solar radiation).

y Atmospheric drag

y

Other effects


37/40

Conclusion: Global Positioning Systems (GPS) give three-dimensional position, velocity and

time information to suitably equip users anywhere on or near the surface of the Earth

(and sometimes off the earth).

Global Navigation Satellite Systems (GNSS) are extended GPS systems, providing

users with sufficient accuracy and integrity information to be useable for critical

navigation applications.

By combining GPS with current and future computer mapping techniques, we will

be better able to identify and manage our natural resources.

Intelligent vehicle location and navigation systems will let us avoid congested

freeways and find more efficient routes to our destinations, saving millions of dollars in

gasoline and tons of air pollution.


38/40

Web Sites:-

www. Garmin.com

www.cc.gatech.edu/ccg

www.ngs.noaa.gov/GPS/GPS.html www.seminars4u.com

www.wikipedia.org/wiki/gps

www.howstuffworks.com

www.gps.com

www.nemisis.in

Reference


39/40


40/40

global positioning sysstem

Documents