old gps

[Jedi Knight Obi-Wan]

I got an old gps 45xl and i cant get it to work.

[+TOMTEC]

Nice, that's a classic unit. Perhaps you can give us a better idea of what the problem is.

Does the unit power up?

Can it see any satellites?

Do you have current firmware installed?

Do you have a data cable to do this?

If you can give a rough idea of your location, I'm sure a local cacher would be more than willing to give you a hand!

Also, if you don't have one, here is a pdf copy of the owners manual for the Garmin GPS45XL

 

Cheers,

TOMTEC

 

I got an old gps 45xl and i cant get it to work.

[+Couparangus]

I remember that unit. The receiver is deaf as a post. Not trying to be funny, but have you tried it outside? My friend has one of these and its basically useless without the external antenna.

[+ZoomZoom]

Jump start it off your car battery.

[+whitecrow]

You may have to adjust it with your light saber.

[+park2]

I seem to remember there was an issue about the GPS clocks rolling over past 1024 weeks or something like that? There was new firmware available for them that fixed that. I don't remember the specifics, it was years ago.

 

Does this ring any bells for anyone else?

[+EraSeek]

I have one. I don't use it anymore but I think it still works. Yes, there was a clock issue. Y2K? I forget. But you had to do a unit reset to get it to pick up the sats again. I forget which buttons you have to push at once to reset it, but Garmin can tell you.

[+Keeper of Maps]

I seem to remember there was an issue about the GPS clocks rolling over past 1024 weeks or something like that? There was new firmware available for them that fixed that. I don't remember the specifics, it was years ago.

 

Does this ring any bells for anyone else?

This was the Epoch problem, and was unrelated to Y2K (though it did happen in 1999). Basically, the GPS system transmits the number of weeks since a certain reference date as part of the time code. This number is held in 10 bits, giving it a maximum value of (2^10)-1 or 1023 (The epoch starts at week 0). At 00:00:00 GPS Time on August 22, 1999, the GPS week number was incremented by 1 from 1111111111 to 10000000000, but because the number is represented by 10 bits only, the leading 1 was dropped, resulting in 0000000000, or week 0 of the 2nd GPS epoch. (The rollover moment took place on August 21 at 23:59:47 UTC because at the time GPS time was leading UTC by 13 seconds.)

 

Early GPS receivers were not designed to account for the roll-over, which is understandable given that a GPS epoch is 19.7 years long. Thus, in August 1999, many receivers suddenly thought it was 00:00:00 UTC on January 6, 1980. This is a problem because the receivers calculate their location in space based on the location of the satellites which are changing in a predictable manner as time marches on.

 

Once the epoch problem was identified, GPS receiver manufacturers came up with various methods of dealing with this ranging from asking the user for the date to storing the date in non-volatile memory to dealing with it in software (e.g. a date cannot be earlier than the release date of the software and if it is then the GPS epoch has changed and is compensated for).

 

For those keeping track, the current GPS epoch ends on April 7, 2019, which is week 2048 (2^11 weeks).

 

When I worked at the Canada Centre for Remote Sensing, GPS receivers were used as time sources at the satellite receiving stations. At least one GPS-based time source had to be replaced because it was not going to handle the rollover properly and Bad Things would happen if the systems thought it was 1980.

 

There's a fairly comprehensive write-up about this problem at http://www.colorado.edu/geography/gcraft/n.../gps/gpseow.htm

[+fizbot]

Yep, great summary Keeper...

Not a Y2K problem, a Y1024K problem :-)

 

I had that problem with my original Micrologic GPS which I describe in my geocache "Accuracy, who needs it?" GCG141

GCG141 Accuracy, Who needs it?

 

As for the original posters problem... as Tomtec said, need more info to troubleshoot.