Computers used anywhere near a GPS receiver can knock your sat-nav system out. Many Intel processors disturb the frequency signals used in GPS systems, a study by the Swedish Defence Research Agency has found.
Using a computer in a car, plane, boat, or anywhere a GPS system is used, can mean that the sat-nav device starts working incorrectly. Many modern processors with high clock frequencies - such as those from Intel with frequencies of 1.7GHz, 2.992GHz and 3.2GHz - have been highlighted as possible sources of interference.
"But these are only examples of processors we have chosen to study. I don't think there would be any difference if we were to pick other types [or processors] since it is the clock frequency of the processor that decides on what frequency the interference occurs," said Peter Stenumgaard at the Swedish Defence Research Agency.
The study showed that modern computers produce interfering signals that reach as far as the frequency bandwidths used for GPS systems (between 1GHz and 2GHz).
It's not that strange that processors using high frequencies can interfere with other equipment. "All electronic devices emit electromagnetic radiation to a certain extent, but some systems are worse than others," Stenumgaard said.
You should be suspicious if your GPS device starts playing up for no apparent reason. "If this happens, try to turn off all near-by electronic systems, such as computers, and see if that stops the problem," he continued.
"If not, you should increase the distance between the GPS receiver and the electronic systems that you think may be interfering."
In the US, the Coast Guard has warned boat owners that certain types of TV antennas can interfere with GPS systems after a number of incidents in which this occured.
These interferences have been measured as far away as 700 metres from the source. They have caused GPS systems to display incorrect position information, or to stop working entirely.
Mobile phones have also been mentioned as possible sources of interference. On one flight, all GPS receivers on a plane stopped working after someone had used their mobile handset mid-air.