Introduction to the Global Positioning SystemAn AAPT/PTRA WorkshopFred NelsonManhattan High School

What is the GPS?Orbiting navigational satellites Transmit position and time dataHandheld receivers calculatelatitudelongitudealtitudevelocityDeveloped by Department of Defense

History of the GPS1969Defense Navigation Satellite System (DNSS) formed1973NAVSTAR Global Positioning System developed1978first 4 satellites launchedDelta rocket launch

History of the GPS199324th satellite launched; initial operational capability1995full operational capabilityMay 2000Military accuracy available to all users

Components of the SystemSpace segment24 satellite vehiclesSix orbital planesInclined 55o with respect to equatorOrbits separated by 60o20,200 km elevation above EarthOrbital period of 11 hr 55 minFive to eight satellites visible from any point on EarthBlock I Satellite Vehicle

The GPS Constellation

GPS Satellite VehicleFour atomic clocksThree nickel-cadmium batteriesTwo solar panelsBattery chargingPower generation1136 wattsS band antennasatellite control12 element L band antennauser communication

Block IIF satellite vehicle (fourth generation)

GPS Satellite VehicleWeight2370 poundsHeight16.25 feetWidth38.025 feet including wing spanDesign life10 yearsBlock IIR satellite vehicle assembly at Lockheed Martin, Valley Forge, PA

Components of the SystemUser segmentGPS antennas & receiver/processorsPositionVelocityPrecise timingUsed byAircraftGround vehiclesShipsIndividuals

Components of the SystemGround control segmentMaster control stationSchreiver AFB, ColoradoFive monitor stationsThree ground antennasBackup control system

GPS Communication and Control

GPS Ground Control Stations

How does GPS work?Satellite rangingSatellite locationsSatellite to user distanceNeed four satellites to determine positionDistance measurementRadio signal traveling at speed of lightMeasure time from satellite to userLow-tech simulation

How does GPS work?Pseudo-Random CodeComplex signalUnique to each satelliteAll satellites use same frequencyAmplified by information theoryEconomical

How does GPS work?Distance to a satellite is determined by measuring how long a radio signal takes to reach us from that satellite. To make the measurement we assume that both the satellite and our receiver are generating the same pseudo-random codes at exactly the same time. By comparing how late the satellite's pseudo-random code appears compared to our receiver's code, we determine how long it took to reach us. Multiply that travel time by the speed of light and you've got distance. High-tech simulation

How does GPS work?Accurate timing is the key to measuring distance to satellites.Satellites are accurate because they have four atomic clocks ($100,000 each) on board. Receiver clocks don't have to be too accurate because an extra satellite range measurement can remove errors.

How does GPS work?To use the satellites as references for range measurements we need to know exactly where they are. GPS satellites are so high up their orbits are very predictable. All GPS receivers have an almanac programmed into their computers that tells them where in the sky each satellite is, moment by moment. Minor variations in their orbits are measured by the Department of Defense. The error information is sent to the satellites, to be transmitted along with the timing signals.

GPS Position Determination

System PerformanceStandard Positioning System100 meters horizontal accuracy156 meters vertical accuracyDesigned for civilian useNo user fee or restrictionsPrecise Positioning System22 meters horizontal accuracy27.7 meters vertical accuracyDesigned for military use

System PerformanceSelective availabilityIntentional degradation of signalControls availability of systems full capabilitiesSet to zero May 2000ReasonsEnhanced 911 serviceCar navigationAdoption of GPS time standardRecreation

System PerformanceThe earth's ionosphere and atmosphere cause delays in the GPS signal that translate into position errors. Some errors can be factored out using mathematics and modeling. The configuration of the satellites in the sky can magnify other errors. Differential GPS can reduce errors.

Application of GPS TechnologyLocation - determining a basic positionNavigation - getting from one location to another Tracking - monitoring the movement of people and things Mapping - creating maps of the world Timing - bringing precise timing to the world

Application of GPS TechnologyPrivate and recreationTraveling by carHiking, climbing, bikingVehicle controlMapping, survey, geologyEnglish Channel TunnelAgricultureAviationGeneral and commercialSpacecraftMaritime

GPS Navigation

GPS Newshttp://www.gpseducationresource.com/gpsnews.htmOnepage reading exerciseCenter of pagemain topicFour cornersquestions & answers from readingFour sidesspecific facts from readingSpaces betweensupporting ideas, diagrams, definitionsArticle citation on back of page

Military Uses for the GPSOperation Desert StormFeatureless terrainInitial purchase of 1000 portable commercial receiversMore than 9000 receivers in use by end of the conflictFoot soldiersVehiclesAircraftMarine vessels

GeocachingCache of goodies established by individualsCoordinates published on WebFind cacheLeave a messageLeave some treasureTake some treasurehttp://www.geocaching.com/

Handheld GPS ReceiversGarmin eTrex~$100Garmin-12~$150Casio GPS wristwatch~$300The GPS Store

GPS Operation JargonWaypoint or LandmarkTrack or HeadingBearingCDIRouteMarkGOTOGPS/Digital Telephone

GPS WebsitesUSNO NAVSTAR HomepageInfo on the GPS constellation How Stuff Works GPSGood everyday language explanationTrimble GPS tutorialFlash animationsGPS Waypoint registryDatabase of coordinates

Classroom ApplicationsPhysicsDistance, velocity, timeOrbital conceptsEarth ScienceMappingSpacecraftEnvironmental ScienceMigratory patternsPopulation distributionsGLOBE ProgramMathematicsGeographyTechnology

Classroom ApplicationsCareersAerospaceSatellite vehiclesLaunch vehiclesHardware engineeringGround control systemsUser systemsSoftware engineeringResearch careers

In and Out of the Classroom

Problem Solving

Sometimes the solution is over your head . . .

Kansas Science Education StandardsStudents will:demonstrate the fundamental abilities necessary to do scientific inquiryapply different kinds of investigations to different kinds of questionsexpand their use and understanding of science and technology

National Science Education Teaching StandardsTeachers of science Plan an inquiry-based science program for their studentsGuide and facilitate learningDesign and manage learning environments that provide students with the time, space, and resources needed for learning science

National Science Education Content Standards. . . all students should develop Abilities necessary to do scientific inquiry Understandings about scientific inquiryAbilities of technological design Understandings about science and technologyUnderstandings aboutMotions and forcesPopulation growth Natural resources Environmental quality Science and technology in local, national, and global challenges

Where does he get those wonderful toys?Student-centeredHigh interest Outdoors High visibility Integrated curriculumInquiry

Thanks for your interest in the Global Positioning SystemFor more information or a copy of these slidesfredlori768@cs.com