Latest Advances in GPS Technology

LATEST ADVANCES IN GPS TECHNOLOGY

Presented by:

M. Gautam Raj

B.Tech, ECE.

Contents

Short review of GPS

Segments of GPS

Functioning of GPS

Applications

Current Technology

Future Technology

Glimpse of Future

Conclusion

Latest Advances in GPS Technology

Global Positioning System

GPS is satellite based Navigational system developed and operated by US department of Defense.

Constellation of 24+ satellites in Earth orbit

Global coverage, 24 hours a day, all weather conditions

Two classes of signals

– Civilian (free of direct user fees)

– Military (encrypted for US/allies)

Signal frequencies

– L1 - 1575.42 MHz (C/A and P-codes)

– L2 - 1227.60 MHz (P-code only)


Segments of GPS

• Space segment

• Control segment

• User segment


Space Segment

• 24 GPS space vehicles (SVs) placed in 6orbits.

• 6 orbital planes inclined at 55 degreeswith the equator.

• Satellites orbit the earth in 12 hrs.

• This constellation provides 5 to 8 SVsfrom any point on the earth.


Control Segment

• The control segment comprises of 5 ground stations located on equator.(4-monitor and 1-master control station)

• Monitor stations measure the distances of the overhead satellites every 1.5 seconds and sends the data to Master control.

• In Master control the satellite orbit, precise time and health of the satellite are determined and determines whether repositioning is required.

• This information is sent back to the satellites using ground antennas.Latest Advances in GPS Technology

User Segment

• It consists of receivers that decodes the signal from the satellites.

• The receiver performs following tasks:

• Selecting 3 or more satellites

• Acquiring GPS signals

• Measuring and tracking

• Acquiring navigation data


How does the GPS work?


Satellites broadcast

• Precise time

• Orbit data

• Satellite health

Receiver measures time delay from satellites, and by triangulation calculates

• Location• Elevation• Velocity

How does the GPS work?

• The GPS uses technique of "triangulation" to find location.

• To "triangulate“, a GPS receiver measures distance from the satellite using the travel timeof radio signals.

• To measure travel time, GPS needs very accurate timing, which is provided by atomicclocks used in the satellites.

• Atomic clocks are the most accurate timekeepers in the world.

• Along with distance, we need to know exactly where the satellites are in space.

• Finally we must correct for any delays


Triangulation


Triangulation


The receiver is somewhere on this sphere.

Signal From One SatelliteSignals From Two Satellites

Three Satellites (2D Positioning)

Three Dimensional (3D) Positioning

Differential GPS

• To obtain more accuratemeasurements than a single GPSunit, DGPS systems are used.

• The GPS unit in the field receivesdata from the GPS satellites andthe other GPS receiver on theground through a radio signal.

• The GPS error from the knownposition is compared to that of theGPS receiver in the unknownlocation.


Applications

• Recreation

• Navigation (Airways ,Waterways & Roadways)

• Construction

• Boundary Mapping

• Surveying

• Search and Rescue

• Precision Agriculture/Forestry


Current Technology

Machine Guidance and Automation


Guidance Systems

Unique opportunities - ability to work accurately

at night

Current Technology

Machine Guidance and Automation


Current Technology

Location of Soldier in War


Current Technology


Wireless and Touch Screens

Future Technology

Dust and Motes


Future Technology


GPS wrist Bands Portable GPS with Music Player

Future Technology


Positioning Head Gear

Autonomous Tractors

Indian Regional Navigation Satellite System

• Indian version of US GPS

-Under ISRO satellite Centre

-It would consist of a constellation of seven satellites and a support ground segment

-Hoping to have all satellites in Orbit by March 2015

• Applications

-Missile Guidance

-Navigation

-Precision Weather Forecast

-Military Applications


Glimpse of the future …

• GNSS (global navigation satellite system) =

Galileo + GPS + GLONASS

• SV constellation

– More than doubled when entire Galileo network is in place

– Improves precision and reliability of the constellation


Summary

• GPS performance is better than ever and will continue to improve

• Enhanced GPS usage

• Integration of wireless technology

• New and cheaper technology



T + 3Then distance between satellite and receiver = “3 times the speed of light”

T

Radio waves travel at the speed of light. If GPS signal leaves satellite at time “T”…

…and is picked up by the receiver at time “T + 3.”

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Latest Advances in GPS Technology

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