GPS – Global Positioning system
J.M Harshani
Department of Civil Engineering
IET, Katunayake
GPS – Global Positioning system
The Term GPS stands for Global Positioning System. The GPS is used to
locate a location with the help of Latitude and Departure. with the help of
GPS it’s possible to locate a point very precisely.
GPS – Global Positioning system
• The Global Positioning System is owned by the United States government and operated
by the United States Space Force. While there are many thousands of civil users of GPS
world-wide, the system was designed for and is operated by the U. S. military.
• The GPS receivers convert the satellite's signals into
position, velocity, and time estimates for
navigation, positioning, or geodesy. Four GPS
satellite signals are used to compute positions in
three dimensions and the time offset in the receiver
clock.
GPS – Global Positioning system
• GPS units are becoming smaller and less expensive, there are
an expanding number of applications for GPS. In transportation
applications, GPS assists pilots and drivers in pinpointing their
locations and avoiding collisions.
• Uncorrected positions determined from GPS satellite signals
produce accuracies in the range of 50 to 100 meters.
Global Position System
Global Positioning System (GPS) -
Is a space-based global navigation satellite system that
provides reliable location and time information in all weather and
at all times and anywhere on or near the Earth when and where
there is an unobstructed line of sight to four or more GPS
satellites.
The GPS consists of three major segments
•Space Segment
•Control Segment
•User Segment
• The space segment
• The space segment consists of 24 satellites, each in
its own orbit 20,200 kilometers above the Earth.
• The nominal GPS Operational Constellation
consists of 24 satellites that orbit the earth in 12
hours.
• There are often more than 24 operational satellites
as new ones are launched to replace older
satellites.
• The satellite orbits repeat almost the same ground
track once each day.
• The orbit altitude is such that the satellites repeat
the same track and configuration over any point
approximately each 24 hours
• There are six orbital planes with nominally four
satellites in each, equally spaced (60 degrees
apart). This constellation provides the user with
between five and eight satelites visible from any
point on the earth.
The control segment
• The Control Segment consists of a system
of tracking stations located around the
world : the GPS Master Control station and
several monitor stations.
• Master Control Stations is located in Colorado
• The Master Control unit, located • 5 Monitoring Station around the globe
at Schriever Air Force Base in Colorado, is • Task of Control Segment
responsible for overall management of the *Computing Satellite Orbital data
*Monitoring satellite clock
remote monitoring and transmission sites.
*Relaying the approximate orbital
data of all satellites
*Relaying information on satellite
health, clock errors etc.
Space Segment
• 24 SVs orbiting in 6 planes 4 satellites in
each orbital plane.
• Each plane 55 ̊ inclination. This ensure that
at least 6 satellites are visible from almost
any were on earth.
• Orbit at an altitude of 20,200km with two
complete orbits each sidereal day.
• Each satellite has a unique Pseudo Random
Noise(PRN) code.
• Has 3 or 4 atomic clocks for precise timing
User Segment
• The user segment of the GPS system consist of
the GPS receivers and the user community.
• GPS receivers convert satellite signals into
positon, velocity ad time estimates.
• Four satellites required to compute the four
dimensions of X, Y, Z(position) and time.
• GPS receivers are used for navigation,
positioning, time dissemination and other
research.
GPS Application
• Traffic Control and Management – Car Navigation OBU (On Board Unit)
– Congestion Information – Cell-Phone-Based Personal
Navigation
– Dynamic Signal Control
– Probe Vehicle Data • Telematics
– Location-Based Information Provision
• Travel Demand Management
• Surveying & Infrastructure
– Pricing
Management
– Mobility Management
– Mapping
• Commercial Vehicle Management
– Land recording (especially in
• Safety and Security developing countries)
– Active/Passive Collision Mitigation – Road Management in Remote Areas
– Unti-theft • Intra-Regional Trade
• Automated Highway • Other modes than auto
• Navigation – Rail, aviation, bicycle, etc
Institute of Engineering Technology, Department of Civil Engineering
Special Instruction Programme – Semester - I
Surveying & Levelling [Electro-Magnetic Distance Measurement – Chapter . 04]
GPS FOR Land Slide Monitoring
Monitoring Land slides
Establish GPS Station in Establish GPS Station
Land Side area in Near by area
GPS for Flood Management
Monitor position • Flood area mapping and demarcation..
change of the stations • Flash flood warning system.
• Getting real time flood height.
• Establishing evacuation shelters.
Land Slide Prediction Land Slide Early Warning
