Introduction to the Global Positioning System. What is the GPS? Orbiting navigational satellites Orbiting navigational satellites Transmit position and.

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

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

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

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

How does GPS work?How does GPS work? Distance to a satellite is determined by measuring how Distance to a satellite is determined by measuring how

long a radio signal takes to reach us from that satellite. long a radio signal takes to reach us from that satellite. To make the measurement we assume that both the To make the measurement we assume that both the

satellite and our receiver are generating the same satellite and our receiver are generating the same pseudo-random codes at exactly the same time. pseudo-random codes at exactly the same time.

By comparing how late the satellite's pseudo-random By comparing how late the satellite's pseudo-random code appears compared to our receiver's code, we code appears compared to our receiver's code, we determine how long it took to reach us. determine how long it took to reach us.

Multiply that travel time by the speed of light and you've Multiply that travel time by the speed of light and you've got distance. got distance.

High-tech simulationHigh-tech simulation

How does GPS work?How does GPS work?

Accurate timing is the key to measuring Accurate timing is the key to measuring distance to satellites.distance to satellites.

Satellites are accurate because they have Satellites are accurate because they have four atomic clocks ($100,000 each) on four atomic clocks ($100,000 each) on board. board.

Receiver clocks don't have to be too Receiver clocks don't have to be too accurate because an extra satellite range accurate because an extra satellite range measurement can remove errors. measurement can remove errors.

How does GPS work?How does GPS work? To use the satellites as references for range To use the satellites as references for range

measurements we need to know exactly where they are. measurements we need to know exactly where they are. GPS satAellites are so high up their orbits are very GPS satAellites are so high up their orbits are very

predictable. predictable. All GPS receivers have an almanac programmed into All GPS receivers have an almanac programmed into

their computers that tells them where in the sky each their computers that tells them where in the sky each satellite is, moment by moment. satellite is, moment by moment.

Minor variations in their orbits are measured by the Minor variations in their orbits are measured by the Department of Defense. Department of Defense.

The error information is sent to the satellites, to be The error information is sent to the satellites, to be transmitted along with the timing signals. transmitted along with the timing signals.

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

Selective availabilitySelective availability Intentional degradation of signalIntentional degradation of signal Controls availability of system’s full capabilitiesControls availability of system’s full capabilities Set to zero May 2000Set to zero May 2000 ReasonsReasons

Enhanced 911 serviceEnhanced 911 service Car navigationCar navigation Adoption of GPS time standardAdoption of GPS time standard RecreationRecreation

System PerformanceSystem PerformanceThe 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 can reduce errors.Differential GPS 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 Timing - bringing precise timing to the Timing - bringing precise timing to the

world 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

Classroom ApplicationsClassroom Applications PhysicsPhysics

Distance, velocity, timeDistance, velocity, time Orbital conceptsOrbital concepts

Earth ScienceEarth Science MappingMapping SpacecraftSpacecraft

Environmental ScienceEnvironmental Science Migratory patternsMigratory patterns Population distributionsPopulation distributions GLOBE ProgramGLOBE Program

MathematicsMathematics GeographyGeography TechnologyTechnology

Classroom ApplicationsClassroom Applications

CareersCareers AerospaceAerospace

Satellite vehiclesSatellite vehicles Launch vehiclesLaunch vehicles

Hardware engineeringHardware engineering Ground control systemsGround control systems User systemsUser systems

Software engineeringSoftware engineering Research careersResearch careers

ConclusionConclusion1.1. GPS is finding its place in every corner of our life. GPS is finding its place in every corner of our life.

Today, we find many applications of GPS all around Today, we find many applications of GPS all around us. us.

2.2. Its like giving every square meter on the planet a Its like giving every square meter on the planet a unique address. In future, the airplanes with GPSRs unique address. In future, the airplanes with GPSRs will be able to land even in dark and in moist will be able to land even in dark and in moist conditions. conditions.

3.3. In no time GPS will be a complete part of our life, just In no time GPS will be a complete part of our life, just as a mobile we have today.as a mobile we have today.