GPS Problem

[boden36]

I have just fired up an old JLR 4510 GPS which has not been used for about 8 years. Was working fine when mothballed. Put a new battery in, performed a master reset and entered correct data in set up.
It took hours to produce a correct position. In the process lots of the info that I had put in during setup was changed. Eg. it is now indicating 11th day of 7th month 1990.
Did these units have a problem with the change of centuries?
Is there something else that can be done to make it work properly?
Does it matter that the settings are incorrect, if the position readings are OK or should I junk it and get a new one?
Regards, Richard.

[ConradG]

Ahh, y2k finally got ya!
Seriously, go to the manufacturer's website and see if they have anything to say. I had to update a glitch in a gps once. It was date specific but wasn't y2k...

[hellosailor]

Some units needed an ephemeris update a while back...maybe that was in 2002? 2000? you should be able to look up this issue and get a better picture of it. And see if your unit suffers from it. VERY FEW were "killed" by this, but "JLR" is a brand I've never heard of, so I'd expect it to be more problematic. If they are still in business, you might try contacting them first.

[scotte]

Here you go: JRC Information 4 September 2007: Notice about Date Data of GPS Receivers

To JRC Global Positioning System (GPS) users:

Customers who utilise GPS date data from the GPS navigator, receiver and plotter, and also GPS receiver installed in the JRC JUE-75A Inmarsat-C models will experience the following phenomena on 17 August 2008 as the date data will output and display 1 January 1989.

The maximum possible duration of the date data from the GPS is 19.6 year. As a result, at 0:00AM (UTC), 17 August 2008, the date data will automatically relapse to the initial commencement date 1 January 1989.

The actual date will be incorrect. The time display and output will not be affected, and the positioning function should operate normally, though may temporarily be interrupted, taking a longer time or fail to fix the position after the date reverts.

Find below list of affected equipment and appropriate countermeasures per model. Contact our service agent or sales representative to arrange countermeasures. Due to age of GPS model concerned, costs for any modifications will be at the customer's expense.

[boden36]

Thanks very much Scotte - that is the information I needed , but really did not want to hear! Looks like the operative word is 'retrofit' , which I guess is company speak for "Our product will fail, and you'll just have to throw the B thing out!"
At least it gives us an excuse to buy a chart plotter.
Regards, Richard.

[scotte]

Or you can just use it and know the date is wrong!

[ConradG]

The only problem may arise from the fact that it may take a long time to initialize and also may find periods where it has trouble finding and intererating the signals that are there because it thinks that the satalites are where they should be based on some previous years data. These are compuers that rely on information or "tables" (if thought of as computerised sextants which the basically are) programmed in. Yes, they do get "live" information from the satalites, but it is possible for them to get confused. With mine, when it no longer had the right "tables", it took forever to 'fix' and would loose it's "fix" sometimes. A download cured the problem.

[steve_hendry]

It really is a sort of Y2K problem. The GPS time is in weeks, where the week number is a 10-bit integer. At week number 1024 (a bit less than 20 years), it rolls over to zero.