What is GPS?What is GPS?

GPSGPS

GGlobal lobal PPositioning ositioning SSystemystem Network of 24 satellites (with spares)Network of 24 satellites (with spares) Developed by Department of DefenseDeveloped by Department of Defense Operational 24 hours/dayOperational 24 hours/day Available worldwideAvailable worldwide Land, sea and airLand, sea and air Works in all weather conditionsWorks in all weather conditions It is FREE!!It is FREE!!

Satellite ConstellationSatellite Constellation

Navigation Tools of the PastNavigation Tools of the Past

SextantSextant ChronometerChronometer

BeginningsBeginnings

TRANSIT developed by Navy in 1960sTRANSIT developed by Navy in 1960s Used to track nuclear submarinesUsed to track nuclear submarines Air Force created own systemAir Force created own system Used to locate vehicles on land or in Used to locate vehicles on land or in

airair

NAVSTARNAVSTAR Combined Navy and Air Force systems Combined Navy and Air Force systems

in 1973in 1973

NAVNAVigation igation SSatellite atellite TTiming iming AAnd nd RRanging (NAVSTARanging (NAVSTAR))

First used in combat during Operation First used in combat during Operation Desert Storm – 1991Desert Storm – 1991

Full Operational Capability – April 27, Full Operational Capability – April 27, 19951995

GPS SystemGPS System

Space Segment – Satellite Space Segment – Satellite ConstellationConstellation

Control Segment– Monitoring Control Segment– Monitoring Stations and Ground AntennasStations and Ground Antennas

User Segment – ReceiversUser Segment – Receivers

GPS SatelliteGPS Satellite

Satellite InformationSatellite Information

Weighs approximately 2,000 lbsWeighs approximately 2,000 lbs

Travels 7,000 mphTravels 7,000 mph

17 feet across with solar panels extended17 feet across with solar panels extended

Last 10 yearsLast 10 years

Orbit 12,500 miles above EarthOrbit 12,500 miles above Earth

Circle the Earth twice dailyCircle the Earth twice daily

How Does GPS Work?How Does GPS Work?

How it worksHow it works

Satellite circles the Earth and transmits Satellite circles the Earth and transmits signalsignal

Signal contains time it was sent and its Signal contains time it was sent and its locationlocation

All satellites send their signal at the same All satellites send their signal at the same timetime

Difference in time to reach receivers is Difference in time to reach receivers is used to determine locationused to determine location

Formula: Distance = Speed x TimeFormula: Distance = Speed x Time

Signal travels at the speed of light – Signal travels at the speed of light – 186,282.3976 miles per second186,282.3976 miles per second

Speed and Time are known, use to Speed and Time are known, use to calculate Distancecalculate Distance

Trilateration Trilateration

Process of measuring the distance Process of measuring the distance from at least three satellites from at least three satellites

Three satellites calculate 2D position Three satellites calculate 2D position (Latitude and Longitude)(Latitude and Longitude)

Four or more satellites calculate 3D Four or more satellites calculate 3D position (Latitude, Longitude, and position (Latitude, Longitude, and Altitude)Altitude)

TrilaterationTrilateration

One satellite can locate a receiver’s position somewhere on a sphere

Two satellites can locate a receiver’s position to a circle representing the intersection of two spheres

Three satellites can locate a receiver’s position to one of two points represented by the intersection of three spheres.

LatitudeLatitude

Latitude lines run horizontalLatitude lines run horizontal Equator is 0°Equator is 0° North and South Poles are 90°North and South Poles are 90°

Lines of Latitude Lines of Latitude

LongitudeLongitude

Also known as meridians, run verticalAlso known as meridians, run vertical The Prime Meridian in Greenwich, The Prime Meridian in Greenwich,

England is 0°England is 0° Lines range from 0° to 180°Lines range from 0° to 180° International Date Line International Date Line

is 180°is 180°

Zoom In button

Zoom Out button

Find button

Page Button

Power Button

Click Stick

Example of a hand held GPS Receiver.

Satellite Page

Map Page Navigation Page

Trip Page Main Menu

Limitations and Limitations and Accuracy with Accuracy with

GPSGPS

Accuracy ProblemsAccuracy Problems

Atmosphere DelayAtmosphere Delay

Signal MultipathSignal Multipath

Receiver Clock ErrorsReceiver Clock Errors

Number of Satellites VisibleNumber of Satellites Visible

Satellite Geometry and shadingSatellite Geometry and shading

Selective Availability – Turned offSelective Availability – Turned off

WAASWAAS

Developed by the FAADeveloped by the FAA

WWide ide AArea rea AAugmentation ugmentation SSystemystem

Increases the accuracy of GPS Increases the accuracy of GPS receiversreceivers

Full Operational Capacity on July 10, Full Operational Capacity on July 10, 20032003

WWide ide AArea rea AAugmentation ugmentation SSystemystem

WAAS

WAAS Reference Station

WAAS Master Station

Receiver

Corrected Signal

Differential CorrectionDifferential Correction

Developed by the Coast GuardDeveloped by the Coast Guard

Also known as DGPSAlso known as DGPS

Ten meter or less accuracyTen meter or less accuracy

Full Operational Capacity March 15, Full Operational Capacity March 15, 19991999

Differential GPSDifferential GPS

Correction Signal

Stationary Receiver

Now what do we do with Now what do we do with this information?this information?

The next section discusses The next section discusses the uses of GPSthe uses of GPS

Uses of GPSUses of GPS

Uses of GPSUses of GPS

LocatingLocating

TrackingTracking

NavigatingNavigating

MappingMapping

TimingTiming

Using GPSUsing GPS

What are uses you can think of?What are uses you can think of?

BoatingBoating FishingFishing

HuntingHunting CampingCamping

HikingHiking BikingBiking

RaftingRafting

Using GPS continuedUsing GPS continued

Scouting from land or air, Horseback Scouting from land or air, Horseback riding, Hot air ballooning, Aviation, riding, Hot air ballooning, Aviation, Snowmobiling, Skiing, Search and Snowmobiling, Skiing, Search and Rescue, Four wheeling, Emergency Rescue, Four wheeling, Emergency Vehicle Tracking, Highway DrivingVehicle Tracking, Highway Driving

Geocaching, Surveying, Military, Geocaching, Surveying, Military, Precision AgriculturePrecision Agriculture

Using GPS continuedUsing GPS continued

Survey disaster areas, Map Survey disaster areas, Map movement of environmental movement of environmental disasters (Oil spills, wild fires, floods, disasters (Oil spills, wild fires, floods, etc)etc)

Mapping fallout shelters, sidewalks, Mapping fallout shelters, sidewalks, streets, trees, trails, etc.streets, trees, trails, etc.

Measuring the growth or decline of Measuring the growth or decline of mountainsmountains

How does GPS improve these How does GPS improve these activities?activities?• Makes the location more preciseMakes the location more precise• User FriendlyUser Friendly• Mapping is easierMapping is easier• Universal systemUniversal system• Fun!Fun!