GPS uses 24 satellites orbiting Earth to allow GPS receivers to determine their precise location by calculating the time delay of signals received from multiple satellites. It provides location, velocity, direction of travel, and accurate time anywhere in the world, 24 hours a day in all weather conditions. GPS involves calculating the distance from the receiver to at least 3 satellites through trilateration to determine a 2D position, or 4 satellites for a 3D position. Its applications include vehicle navigation systems, tracking ship locations, precision agriculture, and scientific data collection.

1. GPS Overview
Presented By: Sakib, Md. Sadman
ID: 13-23482-1

2. What is GPS?
❑ GPS(Global Positioning System) is a type of
GNSS(Global Nevegation Satellite system).
❑ It allows small electronic receivers to determine
the latitude,longitude and altitude of a point.
❑ It uses time signals transmitted along a line of
sight by radio from satellites.
❑ Receivers calculate the precise time as well as
position, which can be used as a reference for
scientific experiments.
❑ GPS uses 24 Medium Earth Orbit satellites (
altitude of about 20,000 kms above the surface of
the earth.

3. What is GPS?
❑ Radio-based navigation system developed by
✓ Initial operation in 1993
✓ Fully operational in 1995
❑ System is called NAVSTAR
✓ NAVigation with Satellite Timing And Ranging
✓ Referred to as GPS
❑ Series of 24 satellites, 6 orbital planes, 4 satellite
vehicles (SV) on each plane
❑ Works anywhere in the world, 24 hours a day, in all
weather conditions and provides:
✓ Location or positional fix
✓ Velocity
✓ Direction of travel
✓ Accurate time

4. Global Navigation Satellite Systems
(GNSS)
❑ NAVSTAR
✓ USA
❑ GLONASS
✓ Russians
❑ Galileo
✓ Europeans

5. Segments Of GPS

6. ❑ Trilateration
✓ Intersection of spheres
❑ SV Ranging
✓ Determining distance from SV
❑ Timing
✓ Why consistent, accurate clocks are required
❑ Positioning
✓ Knowing where SV is in space
❑ Correction of errors
✓ Correcting for ionospheric and tropospheric
delays
GPS involves 5 Basic Steps

7. How GPS works?
❑ Range from each satellite calculated
range = time delay X speed of light
❑ Technique called trilateration is used to
determine your position or “fix”
✓ Intersection of spheres
❑ At least 3 satellites required for 2D fix
❑ However, 4 satellites should always be used
✓ The 4th satellite used to compensate for
inaccurate clock in GPS receivers
✓ Yields much better accuracy and provides 3D
fix

8. HOW TO GET A POSITION
(autonomous positioning = 1 GPS receiver)
❑ Need signal from at least
four SVs for 3D position
❑ One SV provides a time
reference
❑ Distance to three
remaining SVs is
determined by observing
the GPS signal travel time
from SV to the receiver
❑ With three known points,
and distances to each, we
can determine the GPS
receiver’s position
(trilateration)

11. Application Of GPS
Engineering applications
❑ Avionic navigation( autopilot
system) including precision
landing and route correction.
❑ Navigation for ships and boats.
Used by drivers to locate
shipwrecks.
❑ Land and hydrographic
surveying, including topological
surveying, seismic surveys and
rig positioning.
❑ Precise positioning including
bridge section, mining machinery
, construction .
❑ Used in ADC (Anti Collision
Device) in local train system.
Others applications
❑ Vehicle tracking , including in-
car navigation , fleet tracking,
fishing vessel tracking.
❑ Moving maps in automobiles.
❑ Used for trekking , hiking , and
in sports ( to measure exact
speed , distance , time and
altitude ).
❑ Tracking the migratory patterns
of birds , fishes , and animals.
❑ Personal traker. Also used in
security operations.

12. Advantages and Disadvatages of GPS
Advantages
❑ Ease of use.
❑ Accurate , efficient and
absolute recording of position.
❑ High accuracy from remote
location.
❑ A portable and handy tracking
device. Can be used in watches
and hand held devices.
❑ Can be integrated easily with
other communication devices like
mobiles and laptops.
❑ No set up charges.
Disadvantages
❑ Heavy reliance on GPS system.
❑ Ambiguity : GPS signals are not
always accurate. Signals are
affected by reflection from
buildings.
❑ Large cost of maintaining the
satellites.
❑ Geomagnetic storms caused by
solar activity.
❑ The devices are not affordable
to all. Also there is additional
noise and interference in
environment .
❑ Terrorism.

13. Future Scope
❑ The cell phones are increasingly
incorporating GPS technology.
❑ GPS devices in cars will soon be a
commonplace.
❑ 3-D modeling technology in GPS for
anticipating vehicular traffic.
❑ Controlling other devices using your
cell phone.