Gps

Global Positioning

System

INDEX• INTRODUCTION• HISTORY• STRUCTURE• APPLICATIONS• WORKING OF GPS• BASIC CONCEPTS OF GPS• SYSTEM SEGMENTATION• ERROR SOURCES• ANALYSIS• THE SIGNAL• CONCLUSION

INTRODUCTION • GPS is a revolutionary navigation system– 24 satellites orbiting the earth– Provide location within metres or less anywhere on

the globe.– Now available in many cars as an option– Created and operated by the US Department of

Defense

HISTORY• Constellation of 27 satellites– (24 active + 3 spare)

• Orbit 12,600 miles above earth– (10,900 nautical miles)

• Satellites in 12 hour orbit• First satellite launched in 1978, 24th became operational

in 1994• Selective availability was removed in May, 2000– Handheld receivers are now much more accurate

STRUCTURE

Applications of GPS• In-vehicle Navigation (car, boat, airplane)• Asset Management• Construction• Geologic Research & Mining• Military Navigation and Operations• Mapping & Surveying• Precision Agriculture• Public Health • Public Safety• Wireless Communications

WORKING OF GPS• Measuring distance by measuring time

– Satellites send coded signals indicating their position in space and the exact time the signals are being sent

– Receivers use the time it takes signal to travel from satellite to receiver to determine distance from satellite to receiver

– Information from multiple satellites is used to determine position through ‘triangulation’

WORKING OF GPS

BASIC CONCEPTS OF GPS

• A GPS receiver's job is to locate four or more satellites, figure out the distance to each, and use this information to deduce its own location. – Hand-held receivers for recreational use

with accuracy of 10-15 metres– Vehicle mounted receivers for navigation

or agricultural use with accuracy of < 1 metre

– Backpack or tripod mounted receivers for surveying use with accuracy of 5 – 10 centimetres

BASIC CONCEPTS OF GPS• Receivers require clear line-of-sight; thus, they will not

work indoors or where tall objects obscure the sky

The total GPS configuration is comprised of three distinct segments

(1) The space segment-Satellites orbiting the Earth

(2) The control segment-Stations positioned on the Earth’s equator to control the satellites.

(3) The user segment – Anybody that receives and uses the GPS signal.

SYSTEM SEGMENTATIONSYSTEM SEGMENTATION

ERROR SOURCES• Ionospheric and atmospheric delays• Satellite and Receiver clock errors• Dilution of precision• Multipath• Blenders

ANALYSIS• Number of visible satellites• Position dilution of precision• Satellite elevations• Multipath• Distance between space station and rover receivers

A GPS Signal contains three different bits of informationA GPS Signal contains three different bits of information

(1).Pseudo random code(1).Pseudo random code

(2).Ephemeris data(2).Ephemeris data

(3).Almanac data(3).Almanac data

THE SIGNALTHE SIGNAL

GPS was originally designed for military use at any GPS was originally designed for military use at any time, anywhere on the surface of the earth. time, anywhere on the surface of the earth.

The civilians may also use GPS to marine navigation, car The civilians may also use GPS to marine navigation, car navigation and surveyingnavigation and surveying..

CON CLUSIONCON CLUSION