This is a project report on GPS.

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Welcome to Physics Project on
GLOBAL
POSITIONING
SYSTEM
Prepared by : JYOTISMAT RAUL
ROLL NO : 15PHY028
GUIDED BY : DR. B.K. SAHOO
Dept. of Physics, Govt. College (Auto), Angul

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Bonafide certificate
This is to certify that this project report entitled
“GLOBAL POSITIONING SYSTEM ” is the bonafide
work of Mr. JYOTISMAT RAUL , Roll No- 15PHY028
who carried out the research under my supervision during
2017-18 . Certified further, that to the best of my
knowledge the work reported herein does not form part of
any other project report or dissertation on the basis of
which a degree or award was conferred on an earlier
occasion on this or any other candidate.
Supervisor Dr. B.K. Raj
Dr. B.K. Sahoo Reader in Physics
Asst. Prof. of Physics HOD, Dept. of Physics

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Acknowledgements…
I express my sincere and profound thanks to
my project guide Dr. B.K. Sahoo (Asst. Prof.),
M.Sc. ,Ph.D. , for giving me this opportunity to
acquire the real corporate experiences from this
project in his esteemed concern.
I am highly indebted to my passed-out seniors
and friends who inspired me and guided me in every
step of the project work.
I express my sincere thanks to all the
respondents who gave their honest response to my
schedule. I express my profound gratitude to my
family members & friends for their help and
encouragement. I also take this opportunity to thank
all those creative minds and helpful hearts for their
assistance in making this project work.
Jyotismat Raul

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C o n t e n t s . . .
1. Preface
2.What is GPS ?
3.History
4.System Overview
5.Working of GPS
6.GPS Maps
7.Applications
8.Advantages
9.Disadvantages

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ABSTRACT
Global Positioning System (GPS) is the only system
today able to show one’s own position on the earth any time
in any weather, anywhere. This paper addresses this satellite
based navigation system at length. The different segments of
GPS viz. space segment, control segment, user segment are
discussed. In addition, how this amazing system GPS works, is
clearly described. The determination of GPS is also mentioned
with mathematical expressions. The various errors that
degrade the performance of GPS are also included.
DIFFERENTIAL GPS, which is used to improve the accuracy of
measurements, is also studied. The need, working and
implementation of DGPS are discussed at length. Different
types of Maps such as few known Raster and Vector maps
along with Android maps are also described as well. Then
there are explanations about applications of GPS in civilian and
military case and advantages and disadvantages are also
highlighted at brief. Finally, the paper ends with advanced
application of GPS.

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PREFACE
The Global Positioning
System (GPS),
originally NAVSTAR GPS is
a space-based radio
navigation system owned
by the United
States government and
operated by the United
States Air Force. It is
a global navigation satellite system that
provides geolocation and time information to a GPS
receiver anywhere on or near the Earth where there is
an unobstructed line of sight to four or more GPS
satellites.

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What is GPS ?
 It’s a technique by which location of any
object,velocity, direction can be known
precisely at any time on the ground or on the
water surface or in the air.
 GPS was invented by the United States
Department of Defence.
 The actual name of GPS is NAVSTAR
(Navigation System with Time And Ranging).
 This system becomes fully operational in
1994.It was invented by R. L. Easton.
 The GPS consists of 24 satellites (current
32) placed in near circular orbits arranged in
6 orbital planes at 55 degree inclination to
equator at 20,200 KM height orbital radius.
 The period of revolution is 12 hours so
that at least 4 satellites available for
observations at any time throughout the year
anywhere on the world.

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HISTORY OF GPS
# Developed by US Department of
Defence
# 1969 – Defence Navigation Satellite
System (DNSS) formed
# 1973 – NAVSTAR Global Positioning System developed
# 1978 – First 4 satellites launched
# 1993 – 24th
satellite launched; initial operational capability
# 1994 – Full operational capability
# May 2000 – Military accuracy available to all users

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System Overview
Segments of GPS
There are three types of segment i.e.
1. Space Segment
2. Control Segment
3. User Segment

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1. Space Segment
• GPS satellites fly in circular orbit , a semi-major axis of 26 560
km, at a height of 20 200 km .The satellites have a speed of
3.9 km per second and a nominal period of 12 h sidereal time
(11h 58m 2 s).
• Orbital planes are centred on the Earth & each satellite makes
two complete orbits each sidereal day which passes over the
same location on Earth once each day.
• Orbits are designed so that at the very least, six satellites are
always within line of sight from any location on the planet &
the satellites continuously send radio signals towards earth.
• The GPS Space Segment is formed by a satellite constellation
with enough satellites to ensure that the users will have, at
least, 4 simultaneous satellites in view from any point at the
earth surface at any time.

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• The nominal GPS satellite constellation consists of 24 space
vehicles (SVs) distributed in six orbital planes with an
inclination of 55 degrees in relation to the equator. In
addition, the constellation has 3 backup satellites.
Basic functions of satellites-
1) To receive and store data transmitted by the control stations.
2) To maintain accurate time by means of several on-board
atomic clocks.
3) To transmit information and radio signals to users on two L
bands frequencies. L1-1575.42 MHz and L2-1227.60 MHz.
Another additional frequency, L5-1176.45 MHz will be use in
future.
4) To provide stable platform and orbit for the L band
transmitters.
2. Control Segment
The GPS control Segment (also referred to as Ground
Segment or Operational Control System) is responsible for
the proper operation of the GPS system.
The GPS Control Segment is composed by a network of
[A] Monitor Stations (MS),
[B] A Master Control Station (MCS),
[C] A Backup of the MCS
[D] The Ground Antennas (GA)

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The main functions of this segment are
1. Estimate the on board clock status and define the
corresponding parameters to be broadcasted with refer. To
constellation master time.

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2. Define the orbit of each satellite in order to predict the
ephemeris (precise orbital information) along with the
almanac ( coarse orbital information)
3. Determine the attitude (orientation) and location of the
satellites in order to determine the parameters to be sent to
the satellites for correcting their orbits.
4. Uploading the derived clock correction parameters
ephemeris almanac and orbit correction commands to the
satellites.
5. Activation of spare satellites;
6. Resolving satellite anomalies;
7. Passive tracking of satellites.
3.User Segment
User segment consists of GPS receiver- composed of
1. An antenna (internal or external) tuned to the frequencies
transmitted by the satellites
2. Receiver-processors
3. A highly stable Clock (Crystal Oscillator) and
4. A Display System.
• Receiver clock is not as precise as the satellite clock.
• Receivers are classified by its no.of channels-this signifies
signals from how many satellites it can process
simultaneously (4 channels to 48 channels).
• Receiver can relay the position data to a personal computer
or devices. It can interface with other devices using methods
serial connection ,USB or Bluetooth.
• It is operated through many terminals-boaters, ships, pilots,
military, land vehicles etc.

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The major tasks of a receiver are
o Select the satellites in view.
o Acquire the corresponding
signals and evaluate their
health.
o Carry-out the propagation
time measurement
o Calculate the location of the
terminal and estimate the
error.
o Provide accurate time.
Characteristics of GPS
 Free
 Accurate
 Reliable
 Anytime & Almost anywhere
 Unlimited user capacity

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Working of GPS
GPS is based on satellite ranging, i.e. distance from satellites
.... Satellites are precise reference points…
... We determine our distance from them. The GPS satellites
transmit signals on two carrier frequencies.
Determining GPS Position
• Suppose the distance from Satellite A to
our position is 11,000 miles, At this point
we could be located anywhere on the
specified sphere. Next, let’s take
another measurement from a second
satellite i.e. Satellite B
Now our position is narrowed down to the
intersection of these two sphere.
• Taking another measurement from a 3rd
satellite narrows our position down even
further, to the two points. These points
are located where the 3rd sphere cuts
through the intersection of first two sphere. So by ranging
from 3 satellites we can narrow our position to just two
points in space. We could make a 4th
measurement from
another satellite to determine the true point.

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The GPS calculation in the receiver uses four equations in the
four unknowns x, y, z, tc , where x, y, z are the receiver's
coordinates, and c is the time correction for the GPS
receiver's clock. The four equations are:
Where c = speed of light (3 x 108
m/s)
tt,1 , tt,2 , tt,3 = times that GPS satellites 1, 2, 3, and 4,
respectively, transmited their signals (these times are
provided to the receiver as part of the information that is
transmitted).

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tr,1 , tr,2 , tr,3 = times that the signals from " GPS satellites 1,
2, 3, and 4, respectively are received (according to the
inaccurate GPS receiver's clock)
x1, y1, z1 = coordinates of GPS satellite 1 (these coordinates
are provided to the receiver as part. or the information that
is transmitted); similar meaning for x2, y2, z2 etc.
The receiver solves these equations simultaneously to
determine x, y, z, and tc.
METHODS OF POSITIONING
I) Autonomous (10m - 20m)
II) Differential (02m- 05m)
III) Phase-differential (Centimetre)

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SOURCES OF ERROR
1. MULTIPATH
When GPS signals arrive at
the receiver having traveled
different paths.
2. PDOP
PDOP describes error caused by the relative position of the
GPS satellites. 3.SNR (Signal-to-Noise Ratio)
•SNR determines the
signal strength relative to
noise. GPS position is
degraded if the SNR of
one or more satellites in
the constellation falls
below certain range.

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Position of an object located by Satellite 1 only Position of object located by both Satellite 1 & 2
Position of the same object located by three satellites 1,2 & 3 for better accuracy and precision
Position of the same object located by all four satellites for best and accurate cum precised location

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1.Raster Map
A raster map is basically a ‘dumb’ electronic map image
made up of a set number of pixels. You can’t manipulate the
information, move a place name around for example, and
when you zoom into the map, it quickly becomes pixelated
and unreadable, just like a photo taken on a digital camera.
This extract from an OS Land ranger Map is an example of
raster mapping – full of detail and great if all you want to do
is navigate or perhaps overlay some other information, like a
walking route or flood plain.

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2. Vector Map
A vector map, like OS Master Map, is basically a database of
points, lines and polygons which collectively make up all the
features on the map. It’s possible to assign each of these
features extra information – perhaps demographic data and
the age of the buildings for example. Using a Geographic
Information System, or GIS, it’s then possible to do all kinds
of analysis. For instance, you could ask the GIS to highlight
only the buildings older than 50 years, with inhabitants aged
between 30 and 40 living within 10 miles of a certain point.
It’s the ability to do this kind of analysis that makes vector
mapping such a powerful decision making tool.
3. Android Map
i) Street Map
ii) Topographic Map
iii) Aerial Photography

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Applications
GPS has two types of applications i.e.
 Civilian Applications :-
1. Agriculture-
This technology has the potential for providing farmers with
a sophisticated tool to measure yield on much smaller scales
& precise determination and automatic storing of variables
such as field time, working area, machine travel distance and
speed, fuel consumption and yield information.
2. Astronomy-
Both positional and clock synchronization data is used
in astrometry and celestial mechanics. GPS is also used in
both amateur astronomy with small telescopes as well as by
professional observatories for finding extrasolar planets.
3. Disaster relief time & Automated vehicle
Many emergency services depend upon GPS for location and
timing capabilities. Applying location and routes for cars and
trucks to function without a human driver.
4. GPS for mining & Recreation
The use of RTK GPS has significantly improved several mining
operations such as drilling, shovelling, vehicle tracking, and
surveying. RTK GPS provides centimetre-level positioning

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accuracy Geocaching, Geodashing, GPS drawing, way
marking, and other kinds of location based mobile games.
5. Robotics, Sport & Telematics
Self-navigating, autonomous robots using a GPS
sensors, which calculate latitude, longitude, time,
speed, and heading. It is used in computers and Mobile
phones for types of communications.
 Military Applications :-
1. Navigation-
Soldiers use GPS to find objectives, even in the dark or in
unfamiliar territory, and to coordinate troop and supply
movement. In the United States armed forces, commanders
use the Commander's Digital Assistant and lower ranks use
the Soldier Digital Assistant.
2. Target tracking-
Various military weapons systems use GPS to track potential
ground and air targets before flagging them as hostile. These
weapon systems pass target coordinates to precision-guided
munitions to allow them to engage targets accurately.
Military aircraft, particularly in air-to-ground roles, use GPS
to find targets.

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3. Missile and projectile guidance-
GPS allows accurate targeting of various military weapons
including ICBMs, cruise missiles, precision-guided
munitions and artillery shells. Embedded GPS receivers able
to withstand accelerations of 12,000 g or about
118 km/s2
have been developed for use in 155-millimeter
(6.1 in) howitzer shells.
4. Search and Rescue & Reconnaissance-
Patrol movement can be managed more closely.
5. GPS satellites carry a set of nuclear detonation detectors
consisting of an optical sensor called a bhang meter, an X-
ray sensor, a dosimeter, and an electromagnetic pulse (EMP)
sensor (W-sensor), that form a major portion of the United
States Nuclear Detonation Detection System. General
William Shelton has stated that future satellites may drop
this feature to save money.

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Advantages
i. Relatively high positioning accuracies, from tens of meters
level to millimetre level.
ii. Capability of determining velocity and time to an accuracy
commensurate with position.
iii.Signal availability to users anywhere on the globe; in air, on
the ground or at sea.
iv.It is a positioning system with no user charges and uses
relatively low cost hardware.
v. It is an all-weather system available round the clock.
vi.The position information is in three dimension i.e. vertical
and horizontal information is provided. GPS works even if
the points are not intervisible.
Disadvantages
i. Cellular device can track other device users
ii. It is not very cheap
iii. People focus on GPS more than road = accidents
iv.It should be used as back up match but not as 1st
resource
v. It needs good care and handling
vi.It is an external power & It needs batteries (handheld ones)

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BIBLIOGRAPHY
 Linked-in Slideshare. net web
 GPS The movie (2007)
 www.Google.com/wikipedia
 GPS : Theory, algorithms and applications by Guochang Xu
 GPS : Track it , an article in Indian Express , Feb 13,2008

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