U.S. Coast Guard warns on upcoming GPS changes

By Tim Dobbyn

WASHINGTON, Aug 18 (Reuters) - The U.S. Coast Guard on Wednesday urged boaters and other civilian users of the global positioning system to play it safe over the next few days and make sure alternative navigation methods are available.

In a final appeal to private citizens and businesses to check their equipment, the Coast Guard warned that some initial problems for older GPS receivers could begin Thursday although the weekend loomed as the most likely time for units made more than five years ago to shut down or give wrong information.

"Don't rely totally on GPS. You should have some alternative means of navigation," said Capt. Tom Rice, Commander of the U.S. Coast Guard Navigation Center, in Alexandria, Va.

This coming weekend, the 1,024-week time clock in the satellite-based GPS system turns over to zero after nearly 20 years, creating difficulties for some receivers.

Complicating the matter is a major update of time and position data that starts being uploaded to the satellites Thursday. That may confuse some older receivers as the time information will assume the weekend clock rollover.

Designed for the military, the constellation of 27 satellites orbiting 11,000 miles (17,700 kms) above the earth plays an increasingly important role in civilian life.

GPS applications include airline operations, truck fleet tracking and computer maps in cars in addition to allowing boaters to find favorite fishing holes in an otherwise featureless sea.

A less well-known but extremely important use of GPS involves using the precise time signals from the system to coordinate telecommunications networks.

Coast Guard officials told reporters that users needed to be aware of possible problems but not be alarmed. The majority of users were expected to have no problems but the owners of older units were urged to check with manufacturers.

Many makers have developed software patches or new chips to allow older receivers to cope. A list of manufactures and contacts is available on the Internet at

www.navcen.uscg.mil/gps/geninfo/y2k/default.htm.

Rice and other Coast Guard officials at first said the weekend rollover coming up on Aug. 21 at 8.00 p.m. on the U.S. east coast (midnight GMT) was the key time to focus on.

But later they agreed it was impossible to predict how the older GPS units would react to the "almanac" updates to the satellites that begins Thursday at 6.00 p.m. EDT (2200 GMT).

"If it sees something that it just doesn't understand, we are going into an area where anything can happen," said Commander Gary Shank, chief of GPS planning for the Coast Guard.

The U.S. Air Force, which manages the GPS system, told Reuters on Tuesday that the same receiver software bugs that cause problems coping with 20-year clock rollover could trip up the unit on the five-year almanac changes.

In an ironic twist Wednesday, while the Coast Guard was holding its news conference, government scientists were using GPS to measure the height of the Washington Monument. Answer: 555 feet (169 metres), five and nine-tenths inches above the ground.

===================================== End

Ray

-- Ray (ray@totacc.com), August 18, 1999

Answers

Here's the link: Link

Ray

-- Ray (ray@tottacc.com), August 18, 1999.

This link should work:

Link

Ray

-- Ray (ray@tottacc.com), August 18, 1999.

"The U.S. Air Force, which manages the GPS system, told Reuters on Tuesday that the same receiver software bugs that cause problems coping with 20-year clock rollover could trip up the unit on the five-year almanac changes".

This is the frist I've heard about this almanac problem, anyone up on t

-- Anyone (Know@aboutthis.com), August 18, 1999.

Also see this new and quite thorough article about the GPS rollover by Lane Core Jr....

http://www.y2ktimebomb.com/Computech/Issues/lcore9933.htm

"The August 21-22 GPS Rollover: What It Is, And What It Is Not"

-- Linkmeister (link@librarian.edu), August 18, 1999.