GPS

GPS

What is GPS?What is GPS?

GPS is a space based all weather radio navigation system.

GPS

Provides

Position (geographic), Velocity & Time (PVT) Quickly, Economically And

Precisely 24 hours a day, anywhere in the world under the sky

Components of GPSComponents of GPS

Space segmentSpace segment

Control segmentControl segment

User segmentUser segment

Salient stepsSalient stepsSalient stepsSalient steps

1.1. The receiver picks up the signals from the The receiver picks up the signals from the

satellites;satellites;

2.2. Uses signal travel time to calculate distance Uses signal travel time to calculate distance to the satellitesto the satellites

3.3. Using Analytical Principle, position of the Using Analytical Principle, position of the receiver gets calculated.receiver gets calculated.

Space segmentSpace segment

24 satellites 24 satellites

Orbit every 12 hours at 20,200 kmsOrbit every 12 hours at 20,200 kms

4 satellites in each of 6 orbital planes4 satellites in each of 6 orbital planes

Transmit a uniquely coded radio signalTransmit a uniquely coded radio signal

Equipped with onboard atomic standardEquipped with onboard atomic standard

What is so special about an 20200 km orbit?

• ‘Orbits’ twice per day

• Large ‘viewable’ area

Positioning With Satellite

• Satellites are reference points to locations on earth (their location are known)

• A location of a point on earth is identified by “triangulation”

• Travel time of each signal is determined• Signals travel at Speed of light• Distance = Travel Time * Speed of Light

Principle of working using GPS Principle of working using GPS

• The basis of GPS technology is precise measurement of time;

• Use of orbiting satellite position to find location of receiver by method of resection

Pseudoranging

d

One-way ranging in GPS* Sattellite clock generates a signal* Receiver clock detects the signal arrival* The two clocks must keep the same time

Travel time: t=d/c (one way)Distance: d=ct

SS11(x(x11,y,y11,z,z11))

SS22(x(x22,y,y22,z,z22))

SS33(x(x33,y,y33,z,z33)) SS44(x(x44,y,y44,z,z44))

GPS Receiver

1 1 = = {(x{(x11-x)-x)22+(y+(y11-y)-y)22+(z+(z11-z)-z)22} + c.} + c.ΔΔtt

2 2 = = {(x{(x22-x)-x)22+(y+(y22-y)-y)22+(z+(z22-z)-z)22} + c.} + c.ΔΔtt

3 3 = = {(x{(x33-x)-x)22+(y+(y33-y)-y)22+(z+(z33-z)-z)22} + c.} + c.ΔΔtt

44 = = {(x{(x44-x)-x)22+(y+(y44-y)-y)22+(z+(z44-z)-z)22} + c.} + c.ΔΔtt

Principle of GPS PositioningPrinciple of GPS Positioning

(X,Y,Z)(X,Y,Z)

Control segmentControl segment

Ground-based monitoring and upload Ground-based monitoring and upload stationsstations

Control orbit and timing informationControl orbit and timing information

USER

It includes all GPS users. User can receive the GPS signals through antenna connected to the receiver and can determine its position on the surface of the earth

User segmentUser segmentUser segmentUser segment

GPS Receivers;GPS Receivers;

Compatible software for Planning, Compatible software for Planning, Downloading and Processing of GPS Downloading and Processing of GPS receiver data;receiver data;

Some Applications of GPS

Some Applications of GPS

Some Applications of GPS

Some Applications of GPS

GPS Receivers (contd.)GPS Receivers (contd.)

NavigationNavigation capable of about 12 capable of about 12

meter accuracy meter accuracy

light-weight, light-weight, cheap!cheap!

navigation navigation applicationsapplications

GPS data processing software

• Real time

• Post-processing

GPS Coordinate system

• World Geodetic System, 1984 (WGS84)

GPS receivers Positioning Techniques

– Absolute

– Relative

• Real Time

• Post-processing

LIMITATIONS

• Ionospheric delay correction is not possible to compute

• Weak signal – not available under canopy or under shed

• Susceptible to interference

GPS is getting popularas a means for collection

of data

GPS DATA

• Reliable

• Accurate

• Real-time

GPS

Can be used in any conceivable situation

Under the sky

Where the exact position of any object or phenomena involved.

Thank You