Introduction to the Introduction to the Global Positioning SystemGlobal Positioning System

What is the GPS?What is the GPS? Orbiting navigational satellites Orbiting navigational satellites

Transmit position and time dataTransmit position and time data Handheld receivers calculateHandheld receivers calculate

latitudelatitude longitudelongitudealtitudealtitudevelocityvelocity

Developed by Developed by Department Department of Defenseof Defense

History of the GPSHistory of the GPS1969—Defense Navigation Satellite 1969—Defense Navigation Satellite

System (DNSS) formedSystem (DNSS) formed1973—NAVSTAR Global Positioning 1973—NAVSTAR Global Positioning

System developedSystem developed1978—first 4 satellites 1978—first 4 satellites

launchedlaunched

Delta rocket launchDelta rocket launch

History of the GPSHistory of the GPS 1993—24th satellite 1993—24th satellite

launched; initial launched; initial operational capabilityoperational capability

1995—full operational 1995—full operational capabilitycapability

May 2000—Military May 2000—Military accuracy available to accuracy available to all usersall users

Components of the SystemComponents of the SystemSpace segmentSpace segment 24 satellite vehicles24 satellite vehicles Six orbital planesSix orbital planes

Inclined 55Inclined 55o o with respect to with respect to equatorequator

Orbits separated by 60Orbits separated by 60oo

20,200 km elevation above 20,200 km elevation above EarthEarth

Orbital period of 11 hr 55 Orbital period of 11 hr 55 minmin

Five to eight satellites Five to eight satellites visible from any point on visible from any point on EarthEarth

Block I Satellite VehicleBlock I Satellite Vehicle

The GPS ConstellationThe GPS Constellation

GPS Satellite VehicleGPS Satellite Vehicle Four atomic clocksFour atomic clocks Three nickel-cadmium Three nickel-cadmium

batteriesbatteries Two solar panelsTwo solar panels

Battery chargingBattery charging Power generationPower generation 1136 watts1136 watts

S band antenna—satellite S band antenna—satellite controlcontrol

12 element L band antenna—12 element L band antenna—user communicationuser communication

Block IIF satellite vehicle Block IIF satellite vehicle (fourth (fourth generation)generation)

GPS Satellite VehicleGPS Satellite Vehicle

WeightWeight 2370 pounds2370 pounds

HeightHeight 16.25 feet16.25 feet

WidthWidth 38.025 feet including 38.025 feet including

wing spanwing span Design life—10 yearsDesign life—10 years

Block IIR satellite vehicle Block IIR satellite vehicle assembly at Lockheed assembly at Lockheed Martin, Valley Forge, PAMartin, Valley Forge, PA

Components of the SystemComponents of the SystemUser segmentUser segment GPS antennas & receiver/processorsGPS antennas & receiver/processors PositionPosition VelocityVelocity Precise timingPrecise timing Used byUsed by

AircraftAircraft Ground vehiclesGround vehicles ShipsShips IndividualsIndividuals

Components of the SystemComponents of the System

Ground control segmentGround control segmentMaster control stationMaster control station

Schreiver AFB, ColoradoSchreiver AFB, ColoradoFive monitor stationsFive monitor stationsThree ground antennasThree ground antennasBackup control systemBackup control system

GPS Communication and ControlGPS Communication and Control

GPS Ground Control StationsGPS Ground Control Stations

How does GPS work?How does GPS work?

Satellite rangingSatellite rangingSatellite locationsSatellite locationsSatellite to user distanceSatellite to user distanceNeed four satellites to determine positionNeed four satellites to determine position

Distance measurementDistance measurementRadio signal traveling at speed of lightRadio signal traveling at speed of lightMeasure time from satellite to userMeasure time from satellite to user

Low-tech simulationLow-tech simulation

GPS Position DeterminationGPS Position Determination

System PerformanceSystem Performance Standard Positioning Standard Positioning

SystemSystem 100 meters horizontal accuracy100 meters horizontal accuracy 156 meters vertical accuracy156 meters vertical accuracy Designed for civilian useDesigned for civilian use No user fee or restrictionsNo user fee or restrictions

Precise Positioning Precise Positioning SystemSystem 22 meters horizontal accuracy22 meters horizontal accuracy 27.7 meters vertical accuracy27.7 meters vertical accuracy Designed for military useDesigned for military use

System PerformanceSystem Performance

The earth's ionosphere and atmosphere The earth's ionosphere and atmosphere cause delays in the GPS signal that cause delays in the GPS signal that translate into position errors. translate into position errors.

Some errors can be factored out using Some errors can be factored out using mathematics and modeling. mathematics and modeling.

The configuration of the satellites in the The configuration of the satellites in the sky can magnify other errors. sky can magnify other errors.

Differential GPS Differential GPS can reduce errors.can reduce errors.

Application of GPS TechnologyApplication of GPS Technology

Location - determining a basic positionLocation - determining a basic positionNavigation - getting from one location to Navigation - getting from one location to

another another Tracking - monitoring the movement of Tracking - monitoring the movement of

people and things people and things Mapping - creating maps of the world Mapping - creating maps of the world

Application of GPS TechnologyApplication of GPS Technology Private and recreationPrivate and recreation

Traveling by carTraveling by car Hiking, climbing, bikingHiking, climbing, biking Vehicle controlVehicle control

Mapping, survey, geologyMapping, survey, geology English Channel TunnelEnglish Channel Tunnel AgricultureAgriculture AviationAviation

General and commercialGeneral and commercial SpacecraftSpacecraft

MaritimeMaritime

GPS NavigationGPS Navigation

GPS NewsGPS News

http://www.gpseducationresource.com/gpshttp://www.gpseducationresource.com/gpsnews.htmnews.htm

One–page reading exerciseOne–page reading exerciseCenter of page—main topicCenter of page—main topicFour corners—questions & answers from Four corners—questions & answers from

readingreadingFour sides—specific facts from readingFour sides—specific facts from readingSpaces between—supporting ideas, Spaces between—supporting ideas,

diagrams, definitionsdiagrams, definitionsArticle citation on back of pageArticle citation on back of page

Military Uses for the GPSMilitary Uses for the GPS

Operation Desert StormOperation Desert Storm Featureless terrainFeatureless terrain Initial purchase of 1000 portable commercial Initial purchase of 1000 portable commercial

receiversreceivers More than 9000 receivers in use by end of the More than 9000 receivers in use by end of the

conflictconflict Foot soldiersFoot soldiers VehiclesVehicles AircraftAircraft Marine vesselsMarine vessels

Handheld GPS ReceiversHandheld GPS Receivers Garmin eTrexGarmin eTrex

~$100~$100

Garmin-12Garmin-12 ~$150~$150

Casio GPS Casio GPS wristwatchwristwatch ~$300~$300

The GPS StoreThe GPS Store