Presentation on global positioning system GPS

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Global Positioning System (GPS)
P r e s e n t e d B y :
C . U . S . T
< y o u r n a m e h e r e >

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Introduction and Background
• GPS is a very precise navigation and positioning system.
• It is a satellite based navigation system that can give the
user an accurate location on the earth.
• GPS (global positioning system) was originally intended
for US military use but it became available to the public
in 1980.
• GPS can measure latitude, longitude and altitude as well.

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Parts of GPS
• GPS is made up of three parts, these are
satellites(Constellation of 24 satellites),
monitor facilities and user equipment(hand
held receivers).
• All these segments makes up a system
known as GPS.

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Parts of GPS
• SATELLITE:-
1. GPS satellites fly in medium Earth orbit at around
20200km.
2. Each satellite circles the earth twice a day.
3. The satellites are arranged into a six orbital plane
so that 4 satellites are always visible.
4. Their purpose is to accurately detect the location
almost anywhere on the globe.

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Parts of GPS
• Monitor facilities:-
1. Currently there are 5 ground stations around the
world all are maintained by USA.
2. Ground stations calculates the orbital data for
each satellite which keeps them in orbit.
3. They also do any clock corrections in satellite.

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Parts of GPS
• Receivers:-
1. GPS receivers are devices used to incorporate
the signals from the satellite.
2. They can be classified into different types based
on their application.
3. All receivers are generally 12 channel
(Can receive signals from upto 12 satellite).

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How does GPS works?
• GPS uses signals to measure the distance.
I.e; Distance=time x speed of light.
• GPS needs atleast 3 satellites to acquire a
position but four are recommended for
accuracy and to get the third co ordinate
elevation.

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How does GPS works?
•Initially from the first satellite only one distance in know, this
means that we could be anywhere on the globe.
•Buy adding another satellite our position in narrowed down to
two spots which is still not sufficient enough o get us our
position.
•Now buy adding a third satellite, a unique point is obtained
which is our position.
•A fourth satellite is needed to get the elevation.

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Errors in GPS
• Multipath
It is a common error in GPS, it happens when the
signal bounces somewhere before reaching the
receiver.
• SNR
Signal to noise ratio determines the clarity of the
signal . It is uses denoted by signal bars on the
receiver.

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Errors in GPS
• PDOP
Position dilution of precision can occur when
the satellites are note in a well scattered
manner as shown in fig A.
This error can be eliminated when the
satellites are not too close to each other as
shown in fig B.
FIGURE A
FIGURE B

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Advantages of GPS
• Visibility between stations is not necessary.
• Can be used in almost any weather conditions.
• Is user friendly and simple to use.
• Has high precision and accuracy as compared to old
methods.
• Limited calculations are required hence saving time.
• Can measure three dimensional coordinates as well as
velocity.

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Disadvantages of GPS
• Direct visibility of the sky is necessary to acquire the
position. Therefore GPS will not work underground.
• GPS can only provide limited survey needs.
• Requires some skill to properly use it.
• Outdated maps can provide invalid information thus
limiting the use of GPS.
• High cost of instruments.
• Errors of +-10 meters is common

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Uses of GPS
• Data collection and mapping
GPS can be easily used to collect different points
and paths which can then be used to plot maps,
calculate areas etc.
• Navigation
Perhaps the most common use of GPS is
navigation. GPS can easily provide data for
accurate navigation.

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Uses of GPS
• Recreation
GPS can also be used in
recreation activities such as
hiking, trekking, rafting etc

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