PRESENTATION BASED PRESENTATION BASED

ON ON GPSGPS

IntroductionTo GPS

IntroductionTo GPS

• GPS is a spaced based radio GPS is a spaced based radio positioning system, which provide positioning system, which provide suitably equipped user with highly suitably equipped user with highly accurate accurate positionposition, velocity and , velocity and time datatime data

GPS provide specially coded signals GPS provide specially coded signals that can be processed in a GPS that can be processed in a GPS receiver.receiver.

A GPS receiver decodes time signal A GPS receiver decodes time signal transmission from multiple satellites transmission from multiple satellites and calculated its position.and calculated its position.

GPS system was designed & GPS system was designed & controlled by US military.controlled by US military.

The cost of maintaining the system The cost of maintaining the system is approximately US is approximately US $400 million $400 million per year including the replacement per year including the replacement of aging satellite.of aging satellite.

EarthCircumferenc

e24,900

Miles

Rotation1,038

Miles/Hour1 Day Cycle

Moon1/4 Size of the Earth

Distance from Earth

239,000 Miles

Feasibility studies begun in Feasibility studies begun in 1960’s.1960’s.

Pentagon appropriates funding Pentagon appropriates funding in 1973.in 1973.

First satellite launched in 1978.First satellite launched in 1978. System declared fully System declared fully

operational in April, 1995.operational in April, 1995. Open to the public, 2000.Open to the public, 2000.

The History of GPSThe History of GPS

How does GPS work?How does GPS work? Stations on earth, and a GPS Stations on earth, and a GPS

receiver, the distances receiver, the distances between each of these points between each of these points can be calculated. can be calculated.

The distance is calculated The distance is calculated based on the amount of time based on the amount of time it takes for a radio signal to it takes for a radio signal to travel between these points.travel between these points.

Using satellites in the sky, Using satellites in the sky, ground allows the GPS ground allows the GPS receiver to know where you receiver to know where you are, in terms of latitude and are, in terms of latitude and longitude, on the earth.longitude, on the earth.

The more satellites the GPS can “see”, the more accurate your The more satellites the GPS can “see”, the more accurate your reading.reading.

The GPS must “see” the satellites, so it does not work well in The GPS must “see” the satellites, so it does not work well in dense forests, inside caves, underwater, or inside buildings.dense forests, inside caves, underwater, or inside buildings.

GPS SatellitesDistance from

Earth12,000 Miles

2 Orbits in 24 HoursTravel 7,000 MPH

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Satellites Segments

Three major segment of Three major segment of GPS systemGPS system

Space segmentSpace segment Control segmentControl segment User segmentUser segment

Space segment :-Space segment :-

A space segment contain 24 satellites.A space segment contain 24 satellites. The satellite arranged such that a The satellite arranged such that a

minimum of four satellite is in view to a minimum of four satellite is in view to a user at any time on a world wide basis.user at any time on a world wide basis.

Each satellite transmits signals on two Each satellite transmits signals on two radio frequencies, superimposed on radio frequencies, superimposed on which are navigation and system data.which are navigation and system data.

The satellite orbit in six separate The satellite orbit in six separate orbital planes.orbital planes.

Slide 28

24 satellites in six orbital plane 12,000 miles above Earth Orbit twice daily At least 4 satellites in view Distance from Earth to Moon - 256,000 miles

4 satellite in each plane 20,200 km altitude 55 degree inclination.

Control Segment Control Segment The control segment includes a master The control segment includes a master

control station(MCS).control station(MCS). A number of monitor stations, and A number of monitor stations, and

ground antennas throughout the world.ground antennas throughout the world. The master control station, located in The master control station, located in

Colorado Springs.Colorado Springs. Colorado consists of equipment and Colorado consists of equipment and

facilities required for satellite facilities required for satellite monitoring, tracking, commanding, monitoring, tracking, commanding, control, uploading, and navigation control, uploading, and navigation message generation.message generation.

Military.Military. Search and rescue.Search and rescue. Disaster relief.Disaster relief. Surveying.Surveying. Marine, aeronautical and terrestrial Marine, aeronautical and terrestrial

navigation.navigation. Remote controlled vehicle and robot Remote controlled vehicle and robot

guidance.guidance. Satellite positioning and tracking.Satellite positioning and tracking. Shipping.Shipping. Geographic Information Systems (GIS).Geographic Information Systems (GIS). Recreation.Recreation.

User SegmentUser Segment

GPS receiver allows you to pinpoint your GPS receiver allows you to pinpoint your location, anywhere in the world, based on location, anywhere in the world, based on latitude and longitude coordinates.latitude and longitude coordinates.

It can tell you in what direction you are heading.It can tell you in what direction you are heading.

It can show you:It can show you:

how fast you are goinghow fast you are going

your altitudeyour altitude

a map to help you arrive at a destinationa map to help you arrive at a destination

What does a GPS receiver What does a GPS receiver do?do?

Signal From One SatelliteSignal From One SatelliteSignal From One SatelliteSignal From One Satellite

The receiver is somewhere on this sphere.

Signals From Two Signals From Two SatellitesSatellites

Signals From Two Signals From Two SatellitesSatellites

Three Satellites Three Satellites (2D Positioning)(2D Positioning)Three Satellites Three Satellites (2D Positioning)(2D Positioning)

Three Dimensional Three Dimensional (3D) Positioning(3D) Positioning

Three Dimensional Three Dimensional (3D) Positioning(3D) Positioning

How GPS WorksOk, you’re lost, you have amnesia, and you have absolutely no idea where you are. You go up to someone, and like a good amnesiac you ask, “Where Am I?” This person tells you that you are 625 miles from Boise, Idaho. You say, sarcastically, “Wow, that’s some great information. Thanks Buddy.”

We’re Getting Closer

You still have absolutely no idea where you are, so once again you go up to someone and ask, “Where Am I?” This person tells you that you’re 690 miles from Minneapolis. You just scratch your head, but then you start to remember what you learned in GPS class, and, with the US map in your pocket to guide you, you proceed.

Now We Know! You see a another smiling

face and ask “where am I” one more time. This time you get the reply “you are 615 miles from Tucson. The light pops on in your brain. It’s all clear now. You draw three circles extending in the radii of 625 miles from Boise, 690 from Minneapolis, and 615 miles from Tucson. The circles intersect in Denver! Aren’t you glad that you took this class?

GPS by TrilaterationGPS Distance D = Speed of Light x

Time; or D = CT

D

WaypointWaypoint A waypoint is based on coordinates A waypoint is based on coordinates

entered into a GPS receiver’s memory.entered into a GPS receiver’s memory. It can be either a saved position fix, or It can be either a saved position fix, or

user entered coordinates.user entered coordinates. It can be created for any remote point It can be created for any remote point

on earth.on earth. It must have a receiver designated It must have a receiver designated

code or number, or a user supplied code or number, or a user supplied name.name.

Once entered and saved, a waypoint Once entered and saved, a waypoint remains unchanged in the receiver’s remains unchanged in the receiver’s memory until edited or deleted.memory until edited or deleted.

THANK

THANK

SS