final edited gps ppts

8/6/2019 Final Edited Gps Ppts

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A SEMINAR ONGLOBALGLOBAL

POSITIONINGPOSITIONING

SYSTEMSYSTEM ((GPSGPS))

Under guidance of:

Ms.Romya Bhatnagar

Presented by:Presented by:

Aakanksha


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LLISTIST OFOF CONTENTSCONTENTS

What is wireless communication ?

What is gps ?

History of gps.

Why do we need it ?

Principles.

Its components.

How it works ?

Advantages

Limitation

Conclusion


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WWIRELESSIRELESS COMMUNICATIONCOMMUNICATION

Wireless communication is

transfer of information

the over a distance

without the use of

electrical conductors or

"wires".The distances

involved may be short (afew meters as in

television remote control)

or long (thousands or

millions of kilometers for

radio communications).


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DDEFINITIONEFINITION OFOF GPSGPS::

The Global Positioning System, usually called GPS,

is the only fully-functional satellite navigation

system(allow small electronic devices todetermine their location (Longitude, Latitude,

and Altitude) in within a few meters using time

signals transmitted along a line of sight by radio

from satellites. Receivers on the ground with a

fixed position can also be used to calculate theprecise time as a reference for scientific

experiments).


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GLOBAL

POSITIONING

SYSTEM

The Users

System Control

The Birds


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BBRIEFRIEF HISTORYHISTORY OFOF GPSGPS

y NavStar (what we now call GPS)

Started development in 1973

First four satellites launched in 1978 Full Operational Capacity (FOC) reached

on July 17, 1995

System cost of $12 billion

GPS provides both civilian and militarypositioning globally

GPS comprised of three segment


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WWHYHY DODO WEWE NEEDNEED GPS?GPS?

Trying to figure out where you are is

probable mans oldest pastime.

Finally US Dept of Defense decided to form aworldwide positioning system.

Also known as NAVSTAR ( Navigation Satellite

Timing and Ranging Global positioning system)provides instantaneous position, velocity andtime information.


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PRINCIPLESPRINCIPLES


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CCOMPONENTSOMPONENTS OFOF THETHE GPSGPS

Space Segment Control Segment User Segment

GPS


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TTHREEHREE SSEGMENTSEGMENTS OFOF THETHE

GPS:GPS:

Control Segment

Space Segment

User Segment

Master Station Monitor StationsGroundAntennas


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SSPACEPACE SSEGMENTEGMENT::

24 GPS spacevehicles(SVs).

Satellites orbitthe earth in 12

hrs. 6 orbital planes

inclined at 55degrees with theequator.

This constellationprovides 5 to 8SVs from anypoint on theearth.


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CCONTROLONTROL SSEGMENTEGMENT::

The control segment comprises of 5 stations.

They measure the distances of the overhead satellitesevery 1.5 seconds and send the corrected data toMaster control.

Here the satellite orbit, clock performance and healthof the satellite are determined and determineswhether repositioning is required.

This information is sent to the three uplink stations


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UUSERSER SSEGMENTEGMENT::

It consists of receivers that

decode the signals from the

satellites.

The receiver performs following

tasks:

o Selecting one or more satellites

o Acquiring GPS signals

o Measuring and tracking

o Recovering navigation data


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HHOWOW DOESDOES THETHE GPSGPS WORKWORK??

Requirements

Triangulation from satellite

Distance measurement through travel time of

radio signals Very accurate timing required

To measure distance the location of the satelliteshould also be known

Finally delays have to be corrected


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METHODS:METHODS:

The distance from the satellite is determined by thetime it takes for a radio wave to reach the site from thesatellite.

distance = (speed of light) x (time of flight)

This is very simple but there are a few difficulties:o The receiver clock is not exactly synchronized with

the satellite clock so the time of flight will beimprecise.

o The satellite and receiver are in different velocity

reference frames and gravitational regimes .o The speed of light is 300,000 km/s in a vacuum.

However, while traveling through the EarthIonosphere and Troposphere, the radio waves travelat slightly slower speeds.


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TTRIANGULATIONRIANGULATION

Position is calculated

from distance

measurement

Mathematically we

need four satellites

but three are

sufficient by rejecting

the ridiculous answer


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MMEASURINGEASURING DDISTANCEISTANCE

Distance to a satellite is determined by

measuring how long a radio signal takes to

reach us from the satellite

Assuming the satellite and receiver clocks aresync. The delay of the code in the receiver

multiplied by the speed of light gives us the

distance


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TTHREEHREE DDIMENSIONALIMENSIONAL (3D)(3D)

PPOSITIONINGOSITIONING


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EERRORSRRORS

Satellite errorso Errors in modeling clock offset

o Errors in Keplerian representation ofephemeris

o Latency in tracking

Atmospheric propagation errorso Through the ionosphere, carrier experiences

phase advance and the code experiences groupdelay

o Dependent on Geomagnetic latitude

Time of the day

Elevation of the satellite


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RRECEIVERECEIVER EERRORSRRORS AREARE

CCUMULATIVEUMULATIVE!!

User error = +-

1 km


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AAPPLICATIONSPPLICATIONS::

GPS has different uses such as:

o Military

o Navigation

o Mobile satellite communication

o Location based services

o Surveyingo agriculture


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MMILITARYILITARY::

GPS allows accurate targeting of variousmilitary weapons including cruise

missiles andprecision-guided

munitions, as well as improved

command and control of forces

through improved location

awareness.

SURVEYING:SURVEYING:More costly and precise receivers are used by land

surveyors to locate boundaries, structures, and

survey markers, and for road construction.There is also a growing demand for Machine

Guidance such as Automatic Grade Control

systems that use GPS positions plans to

automatically control the blades and buckets of

construction equipment.


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NNAVIGATIONAVIGATION

GPS is used by people around the

world as a navigation aid in cars,

airplanes, and ships. Personal

Navigation Devices(PND) such as

hand-held GPS are used bymountain climbers and hikers.

Glider pilots use the logged signal to

verify their arrival at turn points in

competitions. Low cost GPS

receivers are often combined with

PDAs, cell phones, car computers,or vehicle tracking systems.. The

system can be used to automate

harvesters, mine trucks, and other

vehicles.


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LLOCATIONOCATION--BASEDBASED

SERVICESSERVICES

GPS functionality can be used byemergency services and location-

based services to locate mobile

phones. Assisted GPS is a GPS

technology often used by the mobile

phone because it reduces the power

requirements of the mobile phone

and increases the accuracy of the

location obtained.

AGRICULTUREAGRICULTUREGPS Machine Guidance is used for tractors and other large agricultural

machines via auto steer or a visual aid displayed on a screen, which is

extremely useful for controlled traffic and row crop operations and

when spraying. As well as guidance, GPS used in harvesters with yield

monitors can provide a yield map of the paddock being harvested


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CONCLUSIONSCONCLUSIONS

Global Positioning System (GPS) is currently designed to

provide

navigational accuracy of10 m to 15 m. However, sub

meter accuracy in

differential mode has been achieved and it has been

proved that broad varieties

of problems in geodesy and geo-dynamics can be

tackled through GPS. GPS

service consists of three components, viz. space, control

and user.


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AADVANTAGESDVANTAGES OOFF GPSGPS

allows extremely accurate positioning worldwide in all

kinds of weather.

no need to be able to see stars or landmarks to

accurately position a vessel, vehicle, person or surveymark.

allows surveyor to perform surveys to

accuracy levels impossible conventionally.

quick and economically.

suited to bringing in plane coordinate control

for projects of all types -- boundaries, well

locations, route alignments, mapping control.


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LLIMITATIONSIMITATIONS OOFF GPSGPS

must have clear line of sight to the satellites.

signal is very low in tracking in foliage.

signal would not be discernible at all from the background noise

without the presence of the pseudo-random noise (PRN) codemodulated on the carrier frequency.

Canyons (urban or natural) are areas of very limited usability.

mountains, buildings and trees pose visibility problems.

limited to surface surveys and obstructions to satellite visibility

should be as few as possible.


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Thank you !

final edited gps ppts

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