gps

[Loosehead]

A friend of mine insists that the the GPS system that we more and more rely on is totally at the whim of the USA and they could in time of war for example scramble the signal and effectively nutralise any deivice using GPS. Does anyone know the full story here? Is it true? and if so would they do it? If they did would it cause more problems that it solves? Also is it true that the Russians have their own completely independant equivalent? Can a GPS expert explain, thanks

[kempie]

This pretty much covers it (especially the sections Selective availability and GPS jamming)...

http://en.wikipedia.org/wiki/GPS

The EU is developing its own GPS system Galileo.

http://en.wikipedia.org/wiki/Galileo_positioni ng_system

[Clanad]

We use the system extensively in commercail aviation and it is owned by the U.S. Originally, it was to be the exclusive domain of the Department of Defense but wiser heads prevailed and now the oversight is provided by a mulit-agency. Interestingly, there are tow modes of accurlacy, if you will. One called SPS (Standard Positioning Service) available to anyone provides an accuracy of around of 100m in the horizontal plane and 156m in the vertical plane. These equate to about 95% to 97% accuracy, whereas Precise Positioning Service (PPS) displays 22m in the horizontal plane and 27m in the vertical plane. The refresh rate is higher, obviously, in the PPS mode. By the way, PPS is available, under treaty with most of our allies. The system currently has about 32 satellites, with more planned... To my knowledge, Russia (nor any other country) has an operational GPS system, however it does have limited capability in a pseudo-GPS system called GLONASS and Europe is planning Galileo and, of course, as usual, they've been able to completey and amicably agree on it's design and sharing of costs...
China is considering the cost of thier own system as well...

[kempie]

China officially joined the development of the Galileo Project in 2004.

[jake-the-peg]

Following the September 11, 2001 attacks, the United States Government wrote to the European Union opposing the project, arguing that it would end the ability of the U.S. to shut down GPS in times of military operations.

Nice to know who your friends are isn't it?

[alvin100]

These days it would be virtually impossible to shut down the GPS system anyway, The potential for loss of life and general chaos would be huge, Thousands of ships and small vessels at sea could be lost, as well as aircraft and other machines

[kempie]

The "potential for loss of life" forms part of the risk assessment when military operations are being planned and executed.

In December 2004, President George W. Bush updated the US policy on the management of GPS as a national asset. This saw the Interagency GPS Executive Board being replaced by the National Space-Based Positioning, Navigation, and Timing Executive Committee to advise and coordinate those who implement the directive.

In the name of US national and homeland security this directive instructs The Secretary of Defense to maintain the capability to "Deny to adversaries position, navigation, and timing services from the Global Positioning System... without unduly disrupting civil, commercial, and scientific uses of these services outside an area of military operations, or for homeland security purposes".

http://pnt.gov/policy/

[Toureman]

They would not turn off the GPS system in wartime because it would reduce the efficiency of their own military forces more than the enemy as they could not use it either. They could selectively jam part of it though.