Global Positioning System - GPS referat

Global Positioning System - How does it work?

Topic: GPS / Gallileo:

GPS is also known as Global Positioning System

Since 1960 GPS is developed by US Navy and US Air Force. In 1978 first satellite in spce. In 1983 the US government decided to open the system for civil usage. 1995: Full Operational Capability, FOC. In 2000 the formally integrated deterioration is disabled and within the exactness for civil users is increased from 100 m to 20m.

On the other hand the EU is planning an alternative system. Galileo is the first project of the European Union and the ESA( European Space Agency) and a part of TEN (Trans-European Network). The financing is organized by both organisations.

Galileo will be an alternative Positioning System against the US controlled GPS.

All system specific devices and earth stations will have been created by 2005. In 2004 Galileo wants to start the prototypes. In 2007 all satellites for Galileo will be in orbit.

Finally in 2008, it will be ready for use.

There will be 30 Galileo satellites in the altitude of 24 km. The exactness will be around 1 m.

Structure/functions of GPS:

Space segment:

24 satellites on 6 different orbits

angle of inclination

per orbit 4 satellites

flight altitude 20200 km

control segment:

- 5 worldwide spread earth stations for controlling und observing

Master Control Station in USA

How does GPS work?

The measuring of an precise position takes place through distancemeasures of several satellites on known orbits. The terms of these radio signals is countable throughthese distance measures. To get the precise time the satellites transmit theexact time to the receiver.

3 distance measures are sufficient to get the currentposition.

Method of distance measuring – one waymeasures

We are able to measure the position, the moving direction, the speed andthe altitude.

The following information will be calculated by the GPSreceiver:

distance and direction to the next waypoint, changes of courses, expectedarrival, maximum speed, average speed and many more.

At least 4satellites are needed for a three-dimensional measuring of position (longitude,latitude and altitude)

3 satellites to measure the current position with thex-axis, y-axis and z-axis and one satellite for thetime.

Precision of thesystem

The exactness of the position ranges from 10 to 15 m.Since the 2,May 2000, it can be used by everybodyworldwide.

In excellent conditions the precision increases to3m.

The American military can totally block civil use or canlimit it in crisis zones!

The reason for that is the earth’s atmosphere, becauseradio signals are being refracted.

These are technical and economic conditions for surfacecovering of GPS use in mobile phones, PDAs and clocks. It is possible tointegrate a satellite detection system in nearly each electroniccomponent.

‘The chances fordevelopment are tremendous. We aren’table to foresee all possible kinds of application like the development of computers 20 years ago, of the internet 10 yearsago.‘

L3 -frequency (1381.05 MHz) for the NDS(Nuclear detonation Detection system)

In the last two years various block IIF satellites werelaunched to their proper position in orbit. They were planned to be launched in1998. They are able to broadcast the new L3-frequency. The DoD plans to completethe system till 2009. Every year the administration plans to position 3 newsatellites. 

However, it is to consider that the replacement of theexisting satellites represents only a financial, not a technical problem. If thenew system is a great use to individual users (e.g. aviation, navigation etc..),it is possible that these users contribute to thefinancing.

2004:IIR-M block satellites

-M-code: military use on L1 and L2

-L2C: civil use on L2

availability of the second signaland higher accuracy

2006beginning: IIF block satellite

-new carriersL3: only civil use

third civilsignal, availability, accuracy

Future prospect GALILEO

30satellites, world-wide

1meter exactly


-Developmentphase 2002-2005

-Establishment phase 2006-2007

-startingfrom 2008

*according to news of the day reports American armedforces will be able to switch off likewise in crisis and conflicts the Europeansatellite navigation system GALILEO, like it already happens with the Americanglobal positioning system (GPS).

Safety political reasons andadvantages of GALILEO


smaller susceptibility to interference





(military) efficiency


higher security of the overall system (GPS + GALILEO)              

higher accuracy and breakdown resistance (integrity)

equalsay and control on the part of the European Union

satellite navigation as a billion-market of the future

GALILEOas an element in the total strategy of the European Unio


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