Principles of Global Positioning Principles of Global Positioning Systems and Its ApplicationsSystems and Its Applications

Introduction

The global positioning system(GPS) is a network of 24 NAVSTAR satellites orbiting at a distance of 20,200kms from the surface of the earth . Originally established by the u.s department of defense(DOD).

The system”s positioning and timing data are used for a variety of applications, including air,land and sea navigation, vehicle and vessel tracking,surveying and mapping ,asset and natural Resource management.

GPS is the shortened form of NAVSTAR GPS. This is an acronym for Navigationsystem with Time and Ranging.

Historical Development of GPS

1978 -Launch of first GPS satellite1985 -Kinematic GPS surveying1989 -Launch of first Block II satellite

Wide area differential GPs conceptU.S Coast Guard GPSInformation System (GPSIC)

1993 -Real-time Kinematic GPSInitial operational capability (IOC)on December 8.

1995 -Full operational capability (FOC) on July 171996 -Presendential Decision Directive, first U.S GPS policy2000 - Selective availability set to Zero .

Satellites orbiting the Earth

System Overview:System Overview:

The total GPS configuration is comprised of three The total GPS configuration is comprised of three distinct segmentsdistinct segments

(1) The space segment-Satellites orbiting the Earth(1) The space segment-Satellites orbiting the Earth

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

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

Basic principles of GPSBasic principles of GPS

ResectionResectionFour unknownsFour unknownsCalculating the distance to the Calculating the distance to the

satellitesatelliteCalculating timeCalculating time

Errors and precisionErrors and precision

Ionospheric and atmospheric delaysIonospheric and atmospheric delaysSatellite and Receiver clock errorsSatellite and Receiver clock errorsDilution of precisionDilution of precisionMultipathMultipathBlendersBlenders

Factors affecting accuracyFactors affecting accuracy

Number of visible satellitesNumber of visible satellitesPosition dilution of precisionPosition dilution of precisionSatellite elevationsSatellite elevationsMultipathMultipathDistance between space station and Distance between space station and

rover receiversrover receivers

Differentially corrected positionsDifferentially corrected positionsDGPSDGPS

Surveying with GPSSurveying with GPS

Advantages using GPSAdvantages using GPSLimitations of GPSLimitations of GPSUses of GPS technologyUses of GPS technology

Uses of GPS technologyUses of GPS technology

Location - Determine a basic positionLocation - Determine a basic position Navigation - Getting from one location to Navigation - Getting from one location to

anotheranother Tracking-Monitoring the movement of Tracking-Monitoring the movement of

people and thingspeople and things Mapping-Creating mapsMapping-Creating maps Timing-Providing precise timingTiming-Providing precise timing

Competitors of GPSCompetitors of GPS

GLONASSGLONASS

- Russian Federation’s satellite - Russian Federation’s satellite navigation systemnavigation system

• GalileoGalileo

-European Union and the European -European Union and the European Space AgencySpace Agency

A GPS Signal contains three different bits of information

(1).Pseudo random code

(2).Ephemeris data

(3).Almanac data

Conclusion

GPS was originally designed for military use at any time, anywhere on the surface of the earth. The civilians may also use GPS to marine navigation, car navigation and surveying.

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