GPS uses 24 satellites that orbit the Earth twice a day to transmit navigation signals. GPS receivers triangulate their position by measuring the time delay of signals from multiple satellites. This allows the receiver to calculate distances to the satellites and determine its position on Earth through trilateration. Differential correction improves accuracy by comparing mobile receiver data to that of a fixed base station. GPS has many applications including vehicle navigation systems, tracking devices, and intelligent transportation systems.

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GPS AND ITS APPLICATIONS
SHAHID BASHIR MALIK (1RV19CV410)
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INTRODUCTION
 Geographic information system (GIS) A system that deals with all types of geographically referenced data(i.e. data
storage, representation and manipulation
GPS, which stands for Global Positioning System, is the only system today able to show you your exact position on
the Earth anytime, in any weather, anywhere.
The three parts of GPS are:
Satellites
Receivers
Software

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SATELLITES
There are quite a number of satellites out there in
space. They are used for a wide range of purposes:
satellite TV, cellular phones, military purposes and
etc. Satellites can also be used by GPS receivers.

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GPS SATELLITES
The GPS Operational Constellation consists of 24 satellites that orbit the Earth in very
precise orbits twice a day. GPS satellites emit continuous navigation signals.

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RECEIVERS AND SATELLITES
GPS units are made to communicate with GPS
satellites (which have a much better view of the Earth)
to find out exactly where they are on the global scale
of things.

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GPS SIGNALES
Each GPS satellite transmits data that
indicates its location and the current
time. All GPS satellites synchronize
operations so that these repeating
signals are transmitted at the same
instant.
Physically the signal is just a
complicated digital code, or in
other words, a complicated
sequence of “on” and “off”
pulses.

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TIME DIFFERENCE
The GPS receiver compares the time a
signal was transmitted by a satellite
with the time it was received. The time
difference tells the GPS receiver how
far away the satellite is.

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CALCULATING DISTANCE
Velocity x Time = Distance
Radio waves travel at the speed of light, roughly 186,000
miles per second (mps)
If it took 0.06 seconds to receive a signal transmitted by a satellite
floating directly overhead, use this formula to find your distance
from the satellite.
186,000 mps x 0.06 seconds = 11,160 miles

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Triangulation
Geometric Principle:
You can find one location if you
know its distance from other,
already-known locations.

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Triangulation

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Triangulation

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3-D Trilateration
1 Satellite 2 Satellites
3 Satellites

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Atomic Clocks
GPS satellites use Atomic Clocks for accuracy, but because of the
expense, most GPS receivers do not.

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Line of Sight Transmissions
Line of sight is the ability to draw a straight
line between two objects without any other
objects getting in the way. GPS transmission
are line-of-sight transmissions.
Obstructions such as trees, buildings, or natural
formations may prevent clear line of sight.

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Light Refraction
Sometimes the GPS signal from the
satellite doesn’t follow a straight line.
Refraction is the bending of light as it
travels through one media to another.

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Signal Refraction
Signals from satellites can be like light. When they hit some interference (air patterns in the
atmosphere, uneven geography, etc.) they sometimes bend a little.

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Signal Interference
Sometimes the signals bounce off
things before they hit the receivers.

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Satellite Distribution
When the satellites are all in the same part of the sky, readings will be less
accurate.

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PDOP
All of this combines to make the
signal less accurate, and gives it
what we call a high “PDOP.”
PDOP = Positional Dilution of Precision
11,000 miles
11,000 miles
11,000 miles
11,000 miles
•A PDOP of <4 is excellent
•A PDOP of 4-8 is good
•A PDOP of >8 is poor

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Differential Correction
Differential correction is a
technique that greatly
increases the accuracy of the
collected GPS data. It
involves using a receiver at a
known location - the "base
station“- and comparing that
data with GPS positions
collected from unknown
locations with "roving
receivers."
ISU Base Station - http://134.50.65.125/

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Postprocessing / Real-time
Before
After

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APPLICATIONS
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PUBLIC SAFETY
ENVIRONMENTAL RESOURCES
AVAITION
MILITARY
LOCAL PLANNING
SURVEYING
BUSINESS
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 TRACKING DEVICES
 ONE OF THE EASIEST APPLICATION TO CONSIDER IS TRECKNG DEVICE
 USING “GOTO” FUNCTION THE GPS WILL GUIDE YOU TO A PEDEFINED WAY POINT
USING COMPAS & POINTER
 NAVIGATION
 SPEED :- GPS CLCULATE YOUR GROUND SPED AS YOU RUN DRIVE OR WALK
 ELEVATION:- IN ADDITION TO PROVIDE YOU WITH YOU LATITUDE AND LONITUDE
GPS PROVIDE YOU ALTITUDE INFORMATION
 ITELLIGENT VEHCILE HIGHWAY SYSTEM (IVHS):- IVHS WILL COMBINE GPS
TECHNOLOGY WITH COMMUNICATION ,CONTROL , INFORMATION & NAVIGATION
SYSTEM TO IMPROVE HIGHWAY SAFETY EASE TRACE CONGESTION & REDUCE
HARMFUL ENVIROMENTAL EFFECTS
 CAR NAVIGATION SYSTEM:- A CAR NAVIGATION SYSTEM USES A SPECIALIZED
COMPUTERS THAT USES THE CAR SIGNALS SATELITTES TO TRACK THE DRIVERS
PROGRESS ON A DIGITAL MAP . IT MAY PROVIDE SERVICES LIKE THE SHORTEST
ROUTE ETC.
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The cri cal path is 1 → 3 → 5 → 9
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