Global Positioning System (GPS) ppt

7/28/2019 Global Positioning System (GPS) ppt

1/21

1

Global Positioning System (GPS)


2/21

2

defination The Global Positioning System, usually called GPS, is

the only fully-functional satellite navigation

system(allow small electronic devices to determine their

location (Longitude, Latitude, and Altitude) in within a

few meters using time signals transmitted along a line ofsight by radio from satellites. Receivers on the ground

with a fixed position can also be used to calculate the

precise time as a reference for scientific experiments.)


3/21

3

History Feasibility studies begun in 1960s.

Pentagon appropriates funding in 1973.

First satellite launched in 1978.

System declared fully operational in April, 1995


4/21

4

NAVSTAR:-The United States Department of Defensedeveloped the system, officially named

NAVSTAR GPS (Navigation SignalTiming and Ranging Global PositioningSystem), and launched the firstexperimental satellite in 1978.


5/21

5

GPS NOWADAYS ..? GPS has become a vital global utility, indispensable for

modern navigation on land, sea, and air around the

world, as well as an important tool for map-making and

land surveying. GPS also provides an extremely precise

time reference, required for telecommunications andsome scientific research, including the study of

earthquakes. GPS receivers can also gauge altitude

and speed with a very high degree of accuracy.


6/21

6

Three Parts Space segment

Control segment

User segment


7/21

Space satellite


8/21

8

Space Segment The Air force insures that at least 24

satellites are operational at all times. There are six orbital planes (with

nominally four space vehicles (SVs) ineach), equally spaced (60 degreesapart), and inclined at about fifty-fivedegrees with respect to the equatorial

plane. The satellite orbits are controlled so that

at least six should be available,unobstructed location, at all times.

Each satellite circles the earth twice aday.

Each satellite broadcasts a unique signal that tells the receiver itslocation and the exact time.


9/21

9

Control Segment

The Master Control facility is located at Schriever Air Force Base

(formerly Falcon AFB) in Colorado.

The monitoring stations compute

precise orbital data (ephemeris) andSV clock corrections for each satellite

and update each satellite.

Originally Schriever AFB

and four other stations

monitored and controlled

satellite positions.

During August andSeptember 2005, six more

monitor stations of the NGA

(National Geospatial-

Intelligence Agency) were

added to the grid.

Now, every satellite can be

seen from at least two

monitor stations.


10/21

10

User Segment The primary use of

GPS is navigation.

Navigation receivers

are made for aircraft,ships, ground vehicles,

surveying, and for

hand carrying by

individuals

.


11/21

11

User Segment--cont. The GPS User Segment consists of all GPS

receivers.

Surveying

Recreation

Navigation GPS receivers convert satellite signals into

position, velocity, and time estimates.

Four satellites are required to compute thefour dimensions of X, Y, Z (position) and

Time.


12/21

12


13/21

13

GPS works like this:A minimum of 24 GPS satellites are in orbit at 20,200kilometers (12,600 miles) above the Earth. The satellitesare spaced so that from any point on Earth, at least foursatellites will be above the horizon.Each satellite contains a simple computer, atomic clocks,

and various radios. With an understanding of its own

orbit and the clock, the satellite continually broadcasts itschanging position and time. The satellites use their on-

board atomic clocks to keep precise time, but areotherwise very simple and unsophisticated whencompared to other modern spacecraft.


14/21

14

ApplicationSMilitary

Navigation

Mobile satellite communication

Location based services

Surveying

agriculture


15/21

Military:

GPS allows accurate targeting of various military weapons including cruisemissiles and precision-guided munitions, as well as improved command andcontrol of forces through improved locational awareness. The satellites alsocarry nuclear detonation detectors, which form a major portion of the UnitedStates Nuclear Detonation Detection System. Civilian GPS receivers arerequired to have limits on the velocities and altitudes at which they willreport coordinates.


16/21

16

This taxi in Kyoto

equipped with GPS navigation, isan example of how GPS

technology can be applied in

routine activities.

This is a great little GPS receiverthat lets you know where you are,and where you need to go. It's

Bluetooth so you can use it in yourpocket, with your iPAQ or laptop,and with whichever software yourchoose.

EXAMPLE
http://linuxbrit.co.uk/gadgets/lg/ipaq_gps.jpghttp://linuxbrit.co.uk/gadgets/


17/21

17

GPSErrors Noise

Clock

Biases

Blunder


18/21

18

Noise ErrorNoise errors are the combined effect of :-

Code noise (around 1 meter)

Noise within the receiver noise (around 1meter).


19/21

19

Bias Error Selective Availability (SA)

SA is the intentional degradation of the SPS signals by a time varying

bias. SA is controlled by the DOD to limit accuracy for non-U. S. military

and government users.

Ephemeris data errors: 1 meter

Satellite orbits are constantly changing. Any error in satellite position will

result in an error for the receiver position.

SV clock errors uncorrected by Control Segment can result in one

meter errors.

Tropospheric delays: 1 meter.

The troposphere is the lower part (ground level to from 8 to 13 km) of the

atmosphere that experiences the changes in temperature, pressure, and

humidity associated with weather changes.


20/21

20

Blunder

Blunders can result in errors of hundred ofkilometers.

Control segment mistakes due to computer or

human error can cause errors from one meter to

hundreds of kilometers.

Receiver errors from software or hardware failures

can cause blunder errors of any size.


21/21

21

Global Positioning System (GPS) ppt

Documents