Global Positioning System

World’s most advanced communication system

Group Members

• Aishwaria Patil 70703• Hardik Vasa 70712• Gaurav Patil 70711• Prathik Mohan 70726

Introduction

• The Global Positioning System (GPS) is a Global Navigation Satellite System (GNSS) developed by the United States Department of Defense.

• It uses a constellation of between 24 and 32 Medium Earth Orbit satellites which transmits microwave signals.

• Its official name in Navstar GPS!!

How it all started

• After Korean Air Lines Flight 007 was shot down in 1983 after straying into the USSR's prohibited airspace.

• President Ronald Reagan issued a directive making GPS freely available for civilians like us.

• This is how we use GPS freely today.

First navigation system

• The first satellite navigation system, Transit, used by the United States Navy, was first successfully tested in 1960.

• Using a constellation of five satellites, it could provide a navigational fix approximately once per hour.

Concept of GPS

• GPS device sends data,• GPS device receives data,• Precise timing is done,• Calculates its position,• Again sends data in the next time period. This cycle continuously repeats 25000 times in a

minute!

Four satellites

• Actually 3 satellites are enough for one GPS receiver because earth has only 3 dimensions.

• But the forth satellites is used to correct the error caused in the receiver’s clock.

Rotation System

Position of your receiver

• The position of your receiver is the point of intersection of these four spheres.

• These four spheres are for their functions of height, breath, length and time!

GPS clock

• One of the world’s fastest clock is used in the GPS navigator system.

• Errors are cause due to a very high intensity of light.

• Some of the very expensive clocks has the capability to minimize the errors.

Division of GPS system

1) Space segmentation: 24 GPS satellites and orbiting vehicles.

2) Control segmentation : The flight paths of the satellites are tracked by US Air Force monitoring stations in the world.

3) User segmentation : Consists of the GPS receivers which the user uses it.

Signal frequency

• All satellites broadcast at the same two frequencies, 1.57542 GHz (L1 signal) and 1.2276 GHz (L2 signal).

• Higher signal is superimposed on the low frequency signal.

• And this signal is received by the receiver.

GPS in your computer

How big is the receiver

Disadvantage of GPS

Unless it is safe

Other disadvantages

• Costly affair for maintenance• Uses vary high power• Not applied in rural areas• Does not have a very high speed• Congestion may occur in the satellites due to

over use.

Atmospheric effects

• Inconsistencies of atmospheric conditions affect the speed of the GPS signals as they pass through the Earth's atmosphere (ionosphere ).

• These effects are smallest when the satellite is directly overhead and become greater for satellites nearer the horizon.

Multi path effect

• GPS signals can also be affected by multipath issues, where the radio signals reflect off surrounding terrain; buildings, canyon walls, hard ground, etc.

• These delayed signals can cause inaccuracy.

Applications

• Roads• Space• Aviation• Agriculture

• Marine• Rails• Geo catching

World in your Hand World’s most fastest Communication

GPS GPS