Cell phone glitch throws off GPS

Nextel Communications and Motorola said they are aware of what they describe as a "software issue" that affects the assisted global positioning satellite location services inside possibly hundreds of thousands of Motorola phones. A-GPS (Assisted Global Positioning System), as it's known, determines a location using a combination of software on the phone and information from satellites and the cell phone network.

One of many concerns is how the bug will affect 911 calls. Emergency calls from cell phones must be accompanied by the phone's location, which network operators determine using a number of means. Because the A-GPS fails to boot up, any features that rely on the phone's location, including some emergency calls, Nextel's fleet locating service or its real-time weather updates, are affected to various degrees.

Engineers at Nextel, Motorola and SiRF Technologies, which made the GPS chips inside the cell phones, are trying to find the root cause. Company representatives would not speculate on a possible reason for the problems and declined to comment further.

At least two vendors of software applications using GPS say Motorola i730 phones have experienced problems starting Saturday. In the case of TeleNav, a location and directions provider, the problem fixed itself. But some services offered by family tracking specialist uLocate have been sidelined, according to company co-founder Alan Phillips.

"We're telling our customers to rely on a setting other than Assisted GPS for now" and instead use a default setting that relies on earthbound cell phone base stations, Phillips said.

A prevailing theory is that a time reference used in GPS databases reached its maximum preset number Friday, then reset to zero. The Motorola models may not be able to handle the changes.

The problem is reminiscent of the Y2K glitch, also known as the millennium bug, which stems from an old programming shortcut that used only two digits to signify years, such as "76" for 1976. If computer systems do not get modified, the year 2000 could be interpreted as the year 1900 and crash the system or cause glitches.

As a precaution, Nextel said it has temporarily disabled the transmission of the A-GPS information. But 911 calls will still be accompanied by less accurate location information by using the nearest cell site. "Nextel's 911 service continues to be available throughout the country," the two companies said in a joint statement.

Motorola and Nextel said there have been no instances of problems involving 911 calls, and no examples could be found in cell phone chat rooms such as Howard Forums.

The problem seems to be limited to just cell phones and not other GPS technologies such as handheld navigation aids and package-tracking services.