  GPS satellite and earth images courtesy of NASA |
How does GPS work?
Vehicle gps tracking systems supplied by Pathfinder Vehicle Systems provides a vehicle location accuracy of between 3 and 5 metres.
The first experimental Global Positioning System satellite was launched in 1978 and GPS has now become indispensable for navigation around the world.
Atomic clocks on board the GPS satellites accurate to within one microsecond, also provide a precise time reference used in many applications including scientific study of earthquakes and synchronization of telecommunications networks.
The satellites also carry detectors as part of the United States Nuclear Detonation Detection System.
The system is named NAVSTAR GPS (Navigation Signal Timing and Ranging Global Positioning System). The satellite system is managed by the United States Air Force 50th Space Wing based at Schriever Air Force Base in California. The system is fully maintained by the USAF and it is free for public use.
At an altitude of 12,600 statute miles, each satellite passes over the same location on Earth twice a day. With 30 actively broadcasting satellites, orbits are arranged so that up to 10 satellites are within line of sight from almost anywhere on Earth.
The GPS receiver calculates its position by measuring the distance between itself and three or more GPS satellites. Measuring the time delay between transmission and reception of each GPS radio signal gives the distance to each satellite. The signals also carry information about the satellites' location. By determining the position of and distance to at least three satellites, the receiver can calculate its location.
The new European £20bn Galileo system is due to become operational in 2019 and will offer initial GPS positioning to around 1 metre.
The Galileo system will have five main services:
1, Open access navigation This will be available without charge for use by anyone with appropriate mass-market equipment; simple timing, and positioning down to 1 metre.
2, Commercial navigation (encrypted) High precision to the centimetre; guaranteed service for which service providers will charge fees.
3, Safety Of life navigation Open service; for applications where guaranteed precision is essential. Integrity messages will warn of errors. 4, Public regulated navigation (encrypted) Continuous availability even if other services are disabled in time of crisis; Government agencies will be main users.
5, Search and rescue system will pick up distress beacon locations; feasible to send feedback, e.g. confirming help is on its way.
Ongoing improvements in GPS accuracy will enable the use of automatic and semi automatic vehicle driving systems that are already being developed by vehicle manufacturers.
The first experimental Global Positioning System satellite was launched in 1978 and GPS has now become indispensable for navigation around the world.
Atomic clocks on board the GPS satellites accurate to within one microsecond, also provide a precise time reference used in many applications including scientific study of earthquakes and synchronization of telecommunications networks.
The satellites also carry detectors as part of the United States Nuclear Detonation Detection System.
The system is named NAVSTAR GPS (Navigation Signal Timing and Ranging Global Positioning System). The satellite system is managed by the United States Air Force 50th Space Wing based at Schriever Air Force Base in California. The system is fully maintained by the USAF and it is free for public use.
At an altitude of 12,600 statute miles, each satellite passes over the same location on Earth twice a day. With 30 actively broadcasting satellites, orbits are arranged so that up to 10 satellites are within line of sight from almost anywhere on Earth.
The GPS receiver calculates its position by measuring the distance between itself and three or more GPS satellites. Measuring the time delay between transmission and reception of each GPS radio signal gives the distance to each satellite. The signals also carry information about the satellites' location. By determining the position of and distance to at least three satellites, the receiver can calculate its location.
The new European £20bn Galileo system is due to become operational in 2019 and will offer initial GPS positioning to around 1 metre.
The Galileo system will have five main services:
1, Open access navigation This will be available without charge for use by anyone with appropriate mass-market equipment; simple timing, and positioning down to 1 metre.
2, Commercial navigation (encrypted) High precision to the centimetre; guaranteed service for which service providers will charge fees.
3, Safety Of life navigation Open service; for applications where guaranteed precision is essential. Integrity messages will warn of errors. 4, Public regulated navigation (encrypted) Continuous availability even if other services are disabled in time of crisis; Government agencies will be main users.
5, Search and rescue system will pick up distress beacon locations; feasible to send feedback, e.g. confirming help is on its way.
Ongoing improvements in GPS accuracy will enable the use of automatic and semi automatic vehicle driving systems that are already being developed by vehicle manufacturers.
 GPS satellite on public display at San Diego Aerospace Museum, California, USA |
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