Global positioning system (GPS)

GROUP MEMBERS:
 ANNIE BOSCO
 ANUSREE ASHOKAN
 AYANA C.M.
 BEHJA JASMIN
 CHANDANA R.
 CONFIN S. RAJ
 FEBIN PAUL

CONTENTS
•INTRODUCTION
•HISTORY
• WHAT IS GPS?
•NON US POSITIONING SYSTEM
•USES
• GPS ELEMENTS.
• HOW IT WORKS?
•GPS ERRORS.
• APPLICATIONS
• ADVANTAGES
• DISADVANTAGES
• CURRENT LIMITATIONS
• CONCLUSION.

•Since earliest time, Some of the earliest techniques that travellers used were simple rock
cairns marking the trail, either for finding their way back, repeating their path, or for
others to follow. This technique is still used today. The problems with it, however, are
obvious.
•A better method was to record this spatial information, We call these maps. The first
recorded maps date back to the Mesopotamians some 5,000 years ago, constituting a
revolution in geographic positioning that has enjoyed widespread use ever since.
•Today, we live in a world of precision. We expend great amounts of intellectual and
monetary currency on ever-smaller units of measurement. Knowledge of where we are and
where we are going has, for the past several thousand years, relied on highly trained and
skilled surveyors. The science of surveying has achieved phenomenal levels of precision.
INTRODUCTION

GPS means
• A space-based satellite navigation system provides location
and time information in all weather.
• Maintained by the United States government and is freely
accessible by anyone with a GPS receiver.
WHAT IS GPS?

Official name : “NAVIGATIONAL SATELLITE TIMING AND
RANGING GLOBAL POSITIONING SYSTEM”
(NAVSTAR GPS)
• Consists of 30+ GPS satellites in medium Earth orbit
(2000km - 35,000 km).
• Made up of two dozen satellites working in harmony are known
as a satellite constellation
• Mainly used for navigation, map-making and surveying.

Three segments
1. Space segment.
2. Control segment.
3. User segment.
Space segment Control segment User segment.
TECHNOLOGY OF GPS
 GPS ELEMENTS

USER SEGMENT CONSIST OF RECIEVERS

HOW DOES IT WORKS?
GPS satellites circle the earth twice a day in a very
precise orbit and transmit signal information to earth.
GPS receivers take this information and use
triangulation to calculate the user's exact location.
 GPS receiver compares the time at signal was
transmitted by a satellite with the time when it was
received user's position and display it on the unit's
electronic map.
 A GPS receiver must be locked on to the signal of at
least three satellites to calculate a 2D position (latitude
and longitude) and 3D position.

GPS: HOW DOES IT WORK?
MORE SATELLITE EQUALS BETTER RESOLUTION

SYSTEMATIC SOURCES OF GPS ERROR
•Satellite clock error, ephemeris error
•Atmospheric Refraction
• Ionosphere Refraction
• Troposphere Refraction
• Multipath
• Signal Obstruction
• Selective Availability
• Receiver clock error
• Human Error

APPLICATIONS
GPS is considered a dual-use technology, meaning it has
significant military and civilian applications
 Conflicting Interests
 Military needs a secure system
 Civilians need unrestricted access
GPS IN RAIN FOREST GPS ON BATTLE FIELD

APPLICATIONS
Tracking Devices:
One of the easiest applications to consider is the simple GPS tracking devises.
Navigation:
• Speed GPS’s calculate your ground speed as you walk, run, drive or fly.
Elevation:
In addition to providing you with your latitude and longitude, GPS provides you
with altitude information.
Intelligent Vehicle Highway Systems (IVHS):
IVHS will combine GPS technology with communications, controls, navigation
and information systems to improve highway safety, ease trace congestion, and
reduce harmful environmental effects.
Car Navigation Systems:
A car navigation system uses a specialized computer that use the signals from GPS
satellites to track the driver's progress on a digital map. It may provides services
like the shortest route, etc.

Geographic Information Systems (GIS) :
GPS technology is used extensively in geographic information systems. These
systems combine cellular data networks for communication.
 Aviation:
GPS technology is being applied in aircraft safety systems, air traffic control
system, and zero visibility landing.
GPS technology can be used to plot aircraft altitude to a pitch of one-tenth of
one degree. In future, it is expected to reduce the number of people required in
the control tower and cockpit.
APPLICATIONS

ADVANTAGES OF GPS
 Intervisibility between different stations not required
Not dependent on weather conditions, day or night.
Positional accuracy irrespective of network geometry acts
as a function for two or more different station distance.
Homogeneous accuracy affects geodetic network planning
and could easily establish point with the sites where
stations are not visible e.g. mountains.
Comparatively more flexible, consuming less time and also
more effective.
High accuracy with 3-dimensional geographic information
irrespective of place and time

DISADVANTAGES OF GPS
 GPS chip is power hungry which drains battery in 8 to 12 hours.
This requires either battery replacement or recharge.
 GPS signal does not pierce through the solid walls or structures. Moreover it is affected by
large buildings or structures.
Due to this, user will not be able to utilize GPS service in indoors or under water or in
dense tree regions or in underground stores or places etc.
 GPS accuracy depends on sufficient received signal quality.
GPS signal gets affected due to multipath, atmosphere (i.e. ionosphere), electromagnetic
interference etc. This leads to error of about 5 to 10 meters in GPS signal.
 Though currently system is managed by US DoD and users are utilizing the system free of
cost, it is in the hand of US to allow or deny the GPS service at anytime.
 It is better not to rely completely on GPS system. Backup travel maps with directions will
help in the event of GPS system failure.

CONCLUSION
Previously this service of GPS was confined only the
military and Law enforcements agencies, but now this
is a extended for civilian. GPS provided good
substitute for route mapping in navigation. GPS has
truly helped man to advance in more ways than one. It
is also going to bring a great revolution by its
development. The future will hold a lot more
surprises. Automobiles are tested on moving on their
own without the assistance of a driver.

Global positioning system (GPS)

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