A Dress Rehearsal for Y2K: Are You Ready?

It's serious enough to be called a "dress rehearsal" for the Y2K bug -- yet few people know about it.But if you depend on time and navigational data from the Global Positioning System, or GPS, you need to get ready for August.

GPS is a network of 24 satellites developed by the U.S.Air Force to provide precise timing and navigation information data to the military.Though begun in the 1970s for military use, GPS has become essential for countless civilian uses as well.A broadcast-only radio system, GPS can be accessed by an unlimited number of receivers.In fact, the United States Department of Commerce's Office of Telecommunication report on GPS estimates that there are 10-15 million receivers in use worldwide.And on Saturday, August 21-22, 1999, many of those receivers could be affected by a bug known as the GPS Week Number Rollover, or WNRO.

WNRO refers to the way dates are processed in GPS.GPS satellites track the date by counting the number of weeks up to a total of 1,024.Then, like a car's odometer that rolls over from 99,999 miles to zero, the GPS calendar will reset to zero.Since the GPS calendar started on January 6, 1980, it will reset for the first time starting precisely 13 seconds before midnight Coordinated Universal Time (UTC) on Saturday, Aug.21, 1999.If a GPS receiver has difficulty determining the correct date at, before, during and after this rollover, it may process data incorrectly.In fact, users who depend on GPS for geographic locations on land, at sea or in the air could face serious safety hazards.

Since GPS technology delivers easy, accurate locations and very precise timing information, modern society's use of GPS is widespread.Some GPS receivers are hidden, embedded in a host of other products from car navigation systems to timing devices for electric and telephone utilities.Daily, users devise new applications to enhance productivity in resource management, vehicle and vessel tracking, surveying, environmental protection and restoration, precision agriculture, mining and construction, and scientific research.With all of these uses, the effects of WNRO could be extensive.

GPS receiver problems could range from minor to serious.Some receivers and associated application equipment, such as electronic charting systems, could inaccurately process GPS satellite signals and produce incorrect positions, possibly unknown to the user.On the other hand, some receivers may not be able to locate the satellites and not work at all.Still other receivers may appear to be working while displaying an inaccurate date.Other receivers will be unaffected.Translated into practical terms, this could mean that dispatchers with GPS-based vehicle location systems might find their fleet tracking interrupted.In another situation, a pilot who is not prepared for WNRO might suddenly notice a heading that is off-course.Elsewhere, GPS receivers may not provide necessary information for mariners navigating their ships.These are just a few examples of the problems GPS users could face sooner than they think.

But you can prepare for WNRO.First, check with the manufacturer of your receiver.GPS receiver manufacturers have been testing their products to determine performance status.For example, Trimble of Sunnyvale, Calif.is testing its products and listing them on the company's Internet web site.This site provides a regularly updated Product Status Table that shows how individual Trimble products are anticipated to perform at WNRO and Y2K.To get contact information for other manufacturers, use the company listings below or call the U.S.Government's Y2K hotline at 1-888-USA-4-Y2K.Be prepared to give the manufacturer your receiver's model number, serial number, and the firmware version number or release date that is generally displayed on the startup screen.

Users should also assess the potential risk of having incorrect positions from their GPS receivers at WNRO and Y2K to determine if they should rely on their GPS receivers during these times.And finally, users should not rely on GPS for critical applications where there is a risk to life, critical data or property.

No one can predict precisely how GPS satellites and GPS technology will function in each and every application.Being prepared by following guidelines from GPS manufacturers can reduce the potential for problems, for both WNRO and Y2K.

GPS Manufacturers: