GPS
• Stands for Global Positioning System.
• GPS is used to get an exact location on or above the surface of
the earth (1cm to 100m accuracy).
• Developed by Department of Defense(DoD) and made
available to public in 1983.
• GPS is a very important data input source.
• GPS is one of two (soon to be more) GNSS – Global
Navigation Satellite System.
GNSS
• NAVSTAR (NAVigational Satellite Timing And Ranging
Global Positioning System) – U.S. DoD (“GPS”)
• GLONASS (GLobal Orbiting NAvigational Satellite System)
– Russian system
• Galileo – European system (online in 2019?)
• Compass/BeiDou-2 – Chinese system in development
(operational with 10 satellites as of December, 2011; 35
planned)
• GPS and GLONASS are free to use!
History of GPS
1969—Defense Navigation Satellite System (DNSS) formed.
1973—NAVSTAR Global Positioning System developed.
1978—first 4 satellites launched.
1993—24th satellite launched; initial operational capability.
1995—full operational capability.
May 2000—Military accuracy available to all users.
Basic functions of GPS
• Location – positioning things in space.
• Navigation – getting from point a to point b.
• Tracking - monitoring movements.
• Mapping – creating maps based on those positions.
• Timing – precision global timing.
Components of the system
GPS systems are made up of 3 segments.
Space Segment (SS)
Control Segment (CS)
User Segment (US)
Three Segments of the GPS
Space Segment
User Segment
Control Segment
Ground
Antennas
Master Station Monitor Stations
Space Segment
24 satellite vehicles.
Six orbital planes.
Inclined 55o with respect to equator
Orbits separated by 60o
20,200 km elevation above Earth.
Each satellite circles the Earth twice a day.
Five to eight satellites visible from any point on Earth.
Control Segment
Master control station (The master control station, located at Falcon Air Force
Base in Colorado Springs, Colorado, is responsible for overall management of the remote
monitoring and transmission sites ).
Monitor stations (16 monitoring stations are located throughout the world including
six from the Air force and 10 from the National Geospatial Intelligence Agency(NGA). Each
of the monitor stations checks the exact altitude, position, speed, and overall health of the
).
orbiting satellites
Ground antennas (Four ground antennas co-located with some of the monitor
stations are used to communicate with the GPS satellites for command and control purposes ).
Control Segment
User Segment
GPS antennas & receiver/processors.
Receives the signals from the GPS satellites
and uses the transmitted information to
calculate the user’s three dimensional
position and time.
GPS Uses
• Agriculture
• Surveying
• Navigation (air, sea, land)
• Engineering
• Military operations
• Unmanned vehicle guidance
• Mapping
