GPS uses trilateration to determine a receiver's location based on distance measurements to multiple satellites. The receiver uses signal transit times to calculate distances to at least four satellites. Each distance defines a sphere around the satellite, and the intersection of these spheres pinpoints the receiver's location. GPS consists of three segments - space, control, and user. The space segment consists of 32+ satellites. The control segment monitors and controls the satellites. Users can access GPS for civilian and military navigation, tracking, and timing applications.

2. CONTENTS
• WHAT IS NAVIGATION?
• WHAT IS GPS?
• METHOD
• CALCULATION
• ERROR IN CALCULATION
• THE RESULT
• STRUCTURE
• APPLICATION
• BIBLOGRAPHY

4. The earliest mariners followed the
coast closely to keep from getting
lost. When navigators first sailed into
the open ocean, they discovered that
they could chart their course by
following the stars.
Cavemen probably used stones and
twigs to mark a trail when they set
out hunting for food.

11. trilateration is the process of
determinating absolute or relative
locations of points by measurement of
distances,
using the geometry of circles, spheres or
triangles.

12. Suppose we measure our distance from a satellite and find it to be
10,000 miles.
Knowing that we're 10,000 miles from a particular satellite narrows
down all the possible locations we could be in the whole universe to
the surface of a sphere that is centered on this satellite and has a
radius of 10,000 miles
Next, say we measure our distance to a second satellite and find out
that it's 11,000 miles away.
That tells us that we're not only on the first sphere but we're also on
a sphere that's 11,000 miles from the second satellite. Or in other
words, we're somewhere on the circle where these two spheres
intersect.

13. If we then make a measurement from a third
satellite and find that we're 12,000 miles from that
one, that narrows our position down even
further, to the two points where the 12,000 mile
sphere cuts through the circle that's the
intersection of the first two spheres.
To decide which one is our true location we could make
a fourth measurement

14. In three-dimensional geometry, when it is
known that a point
lies on three surfaces such as the surfaces of
three spheres then
the centers of the three spheres along with
their radii provide
sufficient information to narrow the possible
locations down to no more than two.
If it is known that the point lies on the surface
of a fourth sphere
then knowledge of this sphere's center along
with its radius is sufficient
to determine the one unique location

16. •The receiver uses the messages it receives to determine the
transit
time of each message and computes the distance to each
satellite
using the speed of light.
•Each of these distances and satellites' locations define a
sphere.
The receiver is on the surface of each of these
spheres when the distances and the satellites' locations are
correct.
•These distances and satellites' locations are used to compute
the location
of the receiver using the navigation equations.

17. The x, y, and z components of satellite position and the
time sent are designated as [xi, yi, zi, ti] where the
subscript i denotes the satellite and has the value
1, 2, ..., n, where n>=4. b is receiver's clock bias. The
receiver has four unknowns, the three components of
GPS receiver position and the clock bias [x, y, z, b].

25. CONTROL
SEGMNET
SPACE
SEGMENT
USER
SEGMENT
The current
GPS consists
of three
major
segments.

26. (SS)

28. As of December 2012,there are 32
satellites in the GPS constellation.
The additional satellites improve
the precision of GPS receiver
calculations by providing
redundant measurements. With
the increased number of
satellites, the constellation was
changed to a non uniform
arrangement. Such an
arrangement was shown to
improve reliability and availability
of the system, relative to a uniform
system, when multiple satellites
fail.About nine satellites are visible
from any point on the ground at
any one time

30. (CS)

31. The control segment is composed
of
 a master control station (MCS),
 an alternate master control station,
 four dedicated ground antennas and
 six dedicated monitor stations
The Operation Control
Segment(OCS) currently serves
as the control segment of record.
It provides the operational
capability that supports global
GPS users and keeps the GPS
system operational and
performing within specification

32. in September 2007. After installation, the system helped enable upgrades
and provide a foundation for a new security architecture that supported
the U.S. armed forces. OCS will continue to be the ground control system
of record until the new segment, Next Generation GPS Operation Control
System[2] (OCX), is fully developed and functional. The GPS OCX program
also will reduce cost, schedule and technical risk. It is designed to provide
50%[56] sustainment cost savings through efficient software architecture
and Performance-Based Logistics. In addition, GPS OCX expected to cost
millions less than the cost to upgrade OCS while providing four times the
capability.

33. (US)

36. While originally a military project, GPS is
considered a dual-use technology, meaning
it has significant military and civilian
applications.
GPS has become a widely deployed and
useful tool for commerce, scientific
uses, tracking, and surveillance. GPS's
accurate time facilitates everyday activities
such as banking, mobile phone operations

37. (the study and practice of making MAPS.)
Both civilian and military cartographers use GPS
extensively.
Depend upon GPS for location and timing capabilities.
( )
systems use GPS to locate a vehicle, person, or pet. These devices are
attached to the vehicle, person, or the pet collar.

38. aircraft tracking are systems installed on aircraft to give position reports over
a satellite and/or cellular network.
GPS enables direct fault motion measurement in
earthquakes.
GPS technology integrated with computers and mobile communications
technology in automotive navigation system.

39. Self-navigating, autonomous robots using a GPS sensors, which
calculate latitude, longitude, time, speed, and heading.
Surveyors use absolute locations to make maps and determine
property boundaries.

40. GPS allows soldiers to find objectives, even in the dark or in unfamiliar
territory, and to coordinate troop and supply movement.
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

41. GPS allows accurate targeting of various military weapons including
MISSILES.
Downed pilots can be located faster if their position is known.

42. Wikipedia.