Global Positionning System (G.P.S) M2 ISTRe Feth-Allah DEHMANI Oral Presentation

Global Positionning System  Presentation (When ?, Where ?, Why ?...)  How it works ?  Applications  Limits, competition SUMMARY

Presentation  Invented in 1978 by USA’s defence department  Civilian using allowed in 1985  Can position every place in Earth every time Global Positionning System

Presentation  24 satellites  Elevation = 20,200 Km  Send orbital position and the exact time of emission GPS Transmitters Global Positionning System

Presentation GPS Receptor Electronic card Data treatment Radio transmission NMEA norm Antenna Global Positionning System

How it works How to localize ? For each satellite …  The receptor chooses the maximum visible satellites.  Calculates distance D = S / T  Calculates T = TOR – TOS Global Positionning System  It saves time of sending (TOS) and time of reception of data (TOR).

 1 satellite  somewhere on a sphere. How to localize ?  2 satellites  somewhere on a cercle.  3 satellites  latitude and longitude.  4 satellites  latitude, longitude and altitude. Global Positionning System How it works

NMEA norm  Encryption which allow data processing by a computer.  Datas are sending to the computer with sentences form called frame. Exemple RMC sentence LatitudeLongitude Global Positionning System How it works

Applications Global Positionning System Civilian use  How to reach a place ?  To locate yourself on a map (mountains, deserts…)  Agriculture

Applications Global Positionning System Military use  To guide missiles.  To chase someone.

Limits, competitions Global Positionning System  Impresisions due to the receptor intern clock. (1nS = 30 m)  USA monopoly on this systeme  they can introduce errors on datas emited by satellites.  New GPS satellite have problems with data emitted  It is not consistent with data from the other generation of satellite

Limits, competitions Global Positionning System  Since 1999 : European Positionning system named Galileo - Better accuracy : < 1m - Inform the user within seconds of a failure of any satellite - Ready in 2010

Thank you ! Global Positionning System