Gps by Jhasketan Sahu

  • View
    219

  • Download
    0

Embed Size (px)

Text of Gps by Jhasketan Sahu

  • 7/31/2019 Gps by Jhasketan Sahu

    1/28

    Click to edit Master subtitle style

    GLOBAL POSITIONING

    SYSTEM

    PRESENTED BY ::-

    JHASKETAN SAHU

    0801300154

    CSE (3rd YEAR)

    HI-TECH INSTITUTE OF TECHNOLOGY

  • 7/31/2019 Gps by Jhasketan Sahu

    2/28

    INTRODUCTION

    o TheGPS is a satellite based Radio Navigation

    system, that utilizes precise range measurements

    from the GPS satellites to determine precise

    position anywhere in the world.

  • 7/31/2019 Gps by Jhasketan Sahu

    3/28

    Globe Positioning System (GPS)

    http://maic.jmu.edu/sic/glossary.htm#Projectio

    n

    o GPS is a Satellite NavigationSystem

    o GPS is funded and controlledby the U. S. Department of

    Defense (DOD). While thereare many thousands of civilusers of GPS world-wide, thesystem was designed for andis operated by the U. S.military.

    o GPS provides specially codedsatellite signals that can beprocessed in a GPS receiver,enabling the receiver tocompute position, velocityand time.

    o At least 4 satellites are usedto estimate 4 quantities:position in 3-D (X, Y, Z) and

    GPSing time (T)

    20,000 km

  • 7/31/2019 Gps by Jhasketan Sahu

    4/28

    Components of the GPS

    S p a c e S

    C o n t r o l

    U s e r S e

    G P S

  • 7/31/2019 Gps by Jhasketan Sahu

    5/28

    Space Segment:

    o 24 GPS spacevehicles(SVs).

    o Satellites orbit the

    earth in 12 hrs.o 6 orbital planes

    inclined at 55degrees with the

    equator.o This constellation

    provides 5 to 8SVs from any

    point on the earth.

  • 7/31/2019 Gps by Jhasketan Sahu

    6/28

    Control Segment:

    o The control segment comprises of 5stations.

    o They measure the distances of the overheadsatellites every 1.5 seconds and send thecorrected data to Master control.

    o Here the satellite orbit, clock performanceand health of the satellite are determinedand determines whether repositioning isrequired.

    o

    This information is sent to the three uplinkstations

  • 7/31/2019 Gps by Jhasketan Sahu

    7/28

    User Segment:

    o There are two services SPS and PPSo The Standard Positioning Service

    n SPS- is position accuracy based on GPS

    measurements on single L1 frequencyC/A code

    n C/A ( coarse /acquisition orclear/access) GPs code sequence of

    1023 pseudo random bi phasemodulation on L1 freq

  • 7/31/2019 Gps by Jhasketan Sahu

    8/28

    User Segment:

    o The Precise Position Servicen PPS is the highest level of dynamic

    positioning based on the dual freq P-

    coden The P-code is a very long pseudo-

    random bi phase modulation on the GPScarrier which does not repeat for 267

    daysn Only authorized users, this consists of

    SPS signal plus the P code on L1 and L2and carrier phase measurement on L2

  • 7/31/2019 Gps by Jhasketan Sahu

    9/28

    GPS Satellite Signal:

    o L1 freq. (1575.42 Mhz) carries the SPScode and the navigation message.

    o L2 freq. (1227.60 Mhz) used to measure

    ionosphere delays by PPS receiverso 3 binary code shift L1 and/or L2 carrier

    phasen The C/A coden

    The P coden The Navigation message which is a 50 Hz signal

    consisting of GPs satellite orbits . Clockcorrection and other system parameters

  • 7/31/2019 Gps by Jhasketan Sahu

    10/28

    NAVIGATION

    o Navigation is used forestimating the position of a

    vehicle on sea, in air orand on land to ensure thatthe chosen route is

    followed accurately.

    o GPS satellitesconstellations orbitconsists of 24 satellitesorbiting in 6 orbits,4each.they are orbitingaround earth in every 12hours emitting continuousnavigation signals.

  • 7/31/2019 Gps by Jhasketan Sahu

    11/28

    HOW DOES IT WORK?

    o GPS providesspecially codedsatellite signals thatcan be processed ina GPS receiver,

    enabling the receiverto compute position,

    velocity and time.

    o Four GPS satellitesignals are used tocompute positions inthree dimensions

    and the time offset

    in the receiver clock.

  • 7/31/2019 Gps by Jhasketan Sahu

    12/28

    SATELLITE NAVIGATION

    o This is based onmeasurement of the

    times of arrival of the

    time signals received

    from 3 or more

    orbiting satellites,

    whose positional

    coordinates in space

    are also transmitted.

    o The limiting pulses

    are sent out by eachsatellite in the L-

    Band, using spread

    spectrum modulation

    and are received by

    the GPS Receivers in

  • 7/31/2019 Gps by Jhasketan Sahu

    13/28

    SATELLITE TRANSMISSION

    o The space vehicles transmit two microwave

    carrier signals. The L1 frequency ranging about

    1575.42 MHz carries the navigation message and

    the SPS code signals. The L2 frequency about

    1227.60 MHz is used to measure the ionosphericdelay by PPS equipped receiver.

    o Three types of binary codes are there which shifts

    the L1 and/or L2 carrier phase.

    The C/A Code (Coarse Acquisition) The P-Code (Precise) The Navigation Message

  • 7/31/2019 Gps by Jhasketan Sahu

    14/28

    RECEIVER POSITION, VELOCITY AND

    TIME

    GPS RECEIVER

  • 7/31/2019 Gps by Jhasketan Sahu

    15/28

    POSITION &TIME DETERMINATION

  • 7/31/2019 Gps by Jhasketan Sahu

    16/28

    RADIO NAVIGATION

    o The basis of Global Navigation for an AGV isreliably gaining a co-ordinate of vectordescribing where the vehicle is in relation to afixed point on the globe.

    o This point is generally taken to be theintersection of the Greenwich meridian and theequator line of latitude, at sea level - inaccordance with standard geographical practice.

    o Using this position information, with referenceto a map or otherwise, a list of waypoints can begenerated and followed to allow the vehicle tonavigate between end points of a journey.

  • 7/31/2019 Gps by Jhasketan Sahu

    17/28

    WAYPOINT NAVIGATION

    o A waypoint is an address whichdefines starting point, expected

    destination point, a place to avoid or

    sometimes the intermediate positionalong the way.

    o The Destination Waypointo Routeso Mob (man over board) position waypointo Navigating To Single Way Point

  • 7/31/2019 Gps by Jhasketan Sahu

    18/28

    NASA Landsat-7 (ETM+)

    launched 4/15/1999

    SpectrumVisible

    Near Infrared

    Thermal Infrared

    Bands8

    Resolution (m)

    15, 30, 60

    705 km

  • 7/31/2019 Gps by Jhasketan Sahu

    19/28

    Terra satellite launched

    on 12/18/1999

    http://terra.nasa.gov/About/MODIS/modis_swath.html

    SpectrumVisible

    Near InfraredThermal Infrared

    Bands36

    Resolution (m)250, 500, 1000

    705 km

  • 7/31/2019 Gps by Jhasketan Sahu

    20/28

    Global Geostationary Satellites

    Europe andAfrica

    N. & S.American Eastern

    Pacific

    Jap. Aus. W.Paci

    C. Asia, India China, India

    Earth radius 6,370 kmSatellite altitude 35,800 km

  • 7/31/2019 Gps by Jhasketan Sahu

    21/28

    Image processingand modeling

    Imageprocessing

    andmodeling

    Soil

    moistu

    Surface

    tempert

    Rainf

    all

    E

    T

    Snow

    and

    Wat

    er

    Vegetati

    on

    Lan

    d

    The size of a cell we call image resolution,depending onSuch as 1 m, 30 m, 1 km, or 4 km

  • 7/31/2019 Gps by Jhasketan Sahu

    22/28

    http://www.geoplane.com/gpsneeds.html

  • 7/31/2019 Gps by Jhasketan Sahu

    23/28

    Errors

    o Satellite errorsn Errors in modeling clock offsetn Errors in Keplerian representation of ephemerisn

    Latency in trackingo Atmospheric propagation errors

    n Through the ionosphere,carrier experiencesphase advance and the code experiences groupdelay

    Dependent ono Geomagnetic latitudeo Time of the dayo Elevation of the satellite

  • 7/31/2019 Gps by Jhasketan Sahu

    24/28

    Errors

    o Atmospheric errors can be removed byn Dual freq measurementlow freq get refracted more than high freq

    thus by comparing delays of L1 and L2

    errors can be eliminated

    o Single freq users model the effects of

    the ionosphere

  • 7/31/2019 Gps by Jhasketan Sahu

    25/28

    Errors

    o Troposphere causes delays in code andcarrier

    But they arent freq dependentBut the errors are successfullymodeledo Errors due to Multipatho Receiver noise

  • 7/31/2019 Gps by Jhasketan Sahu

    26/28

    Errors due to geometry

    o Poor GDOPn When angles from

    the receiver to the

    SVs used aresimilar

    o Good GDOPn

    When the anglesare different

  • 7/31/2019 Gps by Jhasketan Sahu

    27/28

    CONCLUSION

    o Though Navigation was someday anunsolved mystery but GPS made itpossible in all types of Navigation suchas Space, Ground and Marine

    Navigations.

    o further researches are making it day byday more useful and the prediction says

    that all the problems regarding positionfixing and determination will be solvedby the development of GPS efficiency

  • 7/31/2019 Gps by Jhasketan Sahu

    28/28

    THANK YOU!!!