By Tracey Logan
Go Digital presenter
Olympic security guards hope to react more quickly to emergencies thanks to an enhanced satellite location system from the European Space Agency (Esa).
Security guards will have PDAs to pinpoint their location
They are the latest users to try out a system called Egnos, the European Geostationary Navigation Overlay Service.
The system assesses the accuracy of satellite positioning signals from the US GPS and Russian Glonass systems.
Earlier trials used it as a navigation aid for blind people, and on buses.
Positioning information from GPS and Glonass satellites can be unreliable if their atomic clocks are inaccurate, their orbits are slightly off track, or if their atmospheric disturbances distort the signal.
Egnos will be able to measure any distortions to the satellite signals through ground-based receiving stations.
The security guards will carry enhanced personal digital assistants (PDAs).
It will send an assessment of their accuracy and integrity to security guards at the Olympics, via one of the system's three geostationary satellites hovering 37,000km above.
The accuracy of the positioning signals to these can now be guaranteed to within three to five metres, thanks to an on-screen reliability display.
Patrol cars at the games will also carry the system.
"The idea is to be more efficient for security and knowing exactly where are all the patrol cars is very important because you don't lose time looking for where the patrol is," Esa's Dominic Detain told the BBC programme, Go Digital.
"With the device in development, you also have the ability to send some images and some sound," he added.
In the event of an emergency at the Olympic Games, a security guard could send an alarm pinpointing his location to a central control room.
Within a second, according a spokesman for Egnos, the guard's exact location in the Olympic complex can be mapped and assistance despatched.
Egnos is the European equivalent of a system called WAAS (the Wide Area Augmentation System) which provides correction information to GPS receivers across North America.
A similar system is also being developed in Japan, the Multi-Functional Satellite Augmentation system (MSAS).
The system has been used by sailors in Greece
Although currently fine-tuning commercially-available satellite positioning receivers in the United States, these systems are ultimately destined for safety-critical applications in future.
Patrick Feuillet of Egnos in Toulouse said that commercial airlines across Europe were planning to install the system by 2005.
It would be used to assure the accuracy of the aircraft's position in the final approach to its destination airport.
For now, the system's final destination is the Olympic Games in Athens.
There, a corps of digitally-enhanced security guards could be breaking records in their rapid response to emergencies.