Introduction to Global Positioning systems and its Applications

Prof. Sumant DasDept. of Civil Engg.

MEFGI, Rajkot

Global Positioning System (GPS)

Global Positioning System (GPS)

In 1973 the U.S. Department of Defensedecided to establish, develop, test, acquire,and deploy a spaceborne Global PositioningSystem (GPS). The result of this decision is thepresent NAVSTAR GPS (Navigation SatelliteTiming And Ranging Global PositioningSystem).

The Global Positioning System (GPS) is a worldwide satellite-based radio navigation systemformed from a constellation of 24 satellites and their ground

stations. It’s used to determine accurate geodetic position & altitude on the earth surface.

Definition of GPS:

Developed by the US Department of Defense

Provides Accurate Navigation

10 - 20 m Worldwide Coverage 24 hour access Common Coordinate System 20,200 Km above the Earth

Designed to replace existing navigation systems

Accessible by Civil and Military

GPS General CharacteristicsGPS General Characteristics

Basic Principles of GPS:

The GPS System Consists of 24 Satellitethat broadcast Signals containing

information about their position and time.

A GPS receiver processes signal from at least 4 Satellites.

The GPS system and receiver is the constancy of the speed of light.

GPS – How it works

All satellites have clocks set to exactly the same time. All satellites know their exact position in space from

data sent to them from the systems controllers. Each satellite transmits its position and a time signal. The signals travel to the receiver delayed only by distance traveled. The receiver calculates the distance to each satellite

and trilaterates its own position.

Types: Single frequency- Static mode GPS surveying Dual frequency- requires post processing only.

GPS Segments

Space Segment Control Segment User Segment

Space Segment24 Satellites

4 satellites in 6 Orbital Planes inclined at 55 Degrees20200 Km above the Earth

12 Hourly orbits In view for 4-5 hours

Designed to last 7.5 yearsDifferent Classifications

Block 1, 2, 2A, 2R & 2 F

Control Segment1Master Control Station

Responsible for collecting tracking data from the monitoring stations and calculating satellite orbits and clock parameters

2.5 Monitoring StationsResponsible for measuring pseudorange data. This orbital tracking network is used to determine the broadcast ephemeris and satellite clock modeling

Ground Control StationsResponsible for upload of information to the

satellites

User Segment1.The most visible segment2 GPS receivers are found in

many locations and applications

Control Segment

Space Segment

User Segment

Three Segments of the GPS

Monitor Stations

GroundAntennas

Master Station

SpaceSpace SegmentSegment 24 Satellites

4 satellites in 6 Orbital Planes inclined at 55 Degrees

20200 Km above the Earth

• 12 Hourly orbits – In view for 4-5 hours

• Designed to last 7.5 years• Different Classifications

– Block 1, 2, 2A, 2R & 2 F

EquatorEquator 55

1

4

3

2

Orbits

Satellites

Control SegmentControl Segment

Master Control Station

Monitor StationGround Antenna

ColoradoSprings

Hawaii AscensionIslands

DiegoGarcia

Kwajalein

Monitor and Control

Control SegmentControl Segment

Master Control Station Responsible for collecting tracking data from the monitoring

stations and calculating satellite orbits and clock parameters

5 Monitoring Stations Responsible for measuring pseudorange data. This orbital

tracking network is used to determine the broadcast ephemeris and satellite clock modeling

Ground Control Stations

Responsible for upload of information to the satellites

User SegmentUser Segment

The most visible segment GPS receivers are found in many

locations and applications

GPS Segments

MonitorStationsMonitorStations

GroundAntennasGround

Antennas AFSCNAFSCN

Master Control StationMaster Control Station

Space Segment

User Segment

Control Segment

Satellite ConstellationSatellite Constellation

Master Control StationMaster Control Station

FAIRBANKS

USNO WASH D.C.

NEW ZEALAND

ECUADOR

ARGENTINA

ENGLAND

BAHRAIN

SOUTH AFRICA

SOUTH KOREA

COLORADO SPRINGS

VANDENBERG, AFB

HAWAIICAPE CANAVERAL

ASCENSIONDIEGO GARCIA

KWAJALEIN

TAHITI

Master Control Station (MCS) Advanced Ground AntennaMaster Control Station (MCS) Advanced Ground Antenna

Ground Antenna (GA)Ground Antenna (GA) Monitor Station (MS)Monitor Station (MS)

National GeospatialNational Geospatial--Intelligence Agency (NGA) Tracking StationIntelligence Agency (NGA) Tracking Station

Alternate Master Control Station (AMCS)Alternate Master Control Station (AMCS)

Who Uses It? Everyone! Merchant, Navy, Coast Guard vessels Commercial Airliners, Civil Pilots Surveyors Commercial Truckers Cars now being equipped Communications and Imaging Satellites

Space-to-Space Navigation Any system requiring accurate timing

Communications

Surveying &Mapping

Fishing &BoatingOff shore

Drilling

Recreation

Trucking & Shipping

Personal Navigation

Aviation

Railroads

Power GridInterfaces

Application of GPS Precision farming

Locations Mapping Monitoring Construction Control Emergency services Boundaries

Agriculture - Slope Staking Tracking of people,

vehicles Sports (boating, hiking,…) Archeology Public Transport Town Planning Hydrographic Surveying Topographical Mapping Cadastral Surveying GIS Application

ApplicationsApplications

Civilian Purpose

Defense Application Navigation (night & bad weather) Call in target coordinates Guidance system for missiles Ships used them for minesweeping,

rendezvous, and aircraft operations