GPS time

[neil_s]

My Furuno GP-30 thinks it's August 1997. I noticed this on first switch-on this year and thought that the keep-alive battery had gone flat. I have had the GPS for about twelve years and it wasn't new when I got it - so I ordered a new battery without thinking any more about it. I have installed the new battery now, but the date problem hasn't gone away - and if I'd read the manual I'd have known that a flat bat triggers a text error message on the screen. Any ideas? The instrument still seems to give an accurate position and the only sign of upset is a small ! next to the incorrect date. Maybe a software problem since it's now 2017?

 

[laika]

My Furuno GP-30 thinks it's August 1997.

It's a GPS rollover issue by the sounds of it: It's 2 years before the next rollover and your display says 2 years before the last rollover. If the manual doesn't mention any date set-up try asking Furuno?

Edit: A little googling turned up some stuff in Finnish and Norwegian. Obviously I speak fluent Finnish (with some help from Mr. Google):
https://translate.google.co.uk/translate?hl=en&sl=fi&u=https://www.furuno.fi/fin/yritys/tiedotteet/2015/06/gps-vastaanottimien-gp-30-ja-gp-35-gps-roll-over/&prev=search

 

[Porthandbuoy]

My Garmin 45 thinks it's August 1997. It might not know when it is, but it does know where it is. There is no 'fix'.
I have it permanently fed from Ladybirds 12Vdc supply and the NMEA 0183 output goes to my DSC VHF.
Other than the date, all the other functions still work fine.

 

[lw395]

What happens if you turn it off, remove the memory battery, then go through a cold start somewhere where the signal is poor?
Does it allow you to enter a time and date to aid acquisition?
And does that date 'stick' or get overwritten?

 

[robmcg]

Laila is indeed correct as it seems to be a rollover issue very similar to ours. I contacted Furunp and their response is detailed below :-

Many thanks for your email help request and I have been tasked with trying to assist you with your recent enquiry.

I am afraid that the unit has suffered from what is known as GPS roll over and is potentially at the end of its life, I have tried to explain this in greater detail below which you will hopefully understand.

The GPS week number count is reset every 1024 weeks which roughly equates to 19.6 years. Time of the week count and GPS week number count make up a total of 29-bits, 19 of the least significant bits are for the TOW (time of week) count and the remaining 10 bits are for the week number count. The 10 bits for the week in number format count up as 1,2,4,8,16,32,64,128,256,512, *10 bits can only count to 1023 before rolling over, adding all the previous numbers listed (1-512) will add to 1023 and at this point the chip will roll over and reset. After rolling over depending on programming the unit may suffer consequences but never really sure until they happen, have placed some examples below:

• It may revert back to a date programmed into its memory (EEPROM) or simply revert back 19.6 years in time to the start all over again from the beginning.
• It may sense an error and refuse to calculate a position all together.
• It may display incorrect positions as they incorrectly determine the position of the satellites from the ephemeris transmitted inside the navigation message, ephemeris = a table or data file giving the calculated positions of a celestial object at regular intervals throughout a period of time.

In this instance it looks like the unit has wound itself back 19.6 years to original program date/time, you can wait a couple of weeks to see if this sorts itself out but I don’t think it will and unfortunately there is no fix other than to purchase a new unit such as the GP-32.

If you decide to live with the date being incorrect then I would however check the positional accuracy of the equipment now just in case it is calculating an incorrect position.

Please see the link below for a list of UK dealers so you can find the one relevant/closest to your location should you wish to enquire about purchasing a new unit, The GP39 is the same physical size as your GP-30 with the addition of a colour display:

 

[laika]

The somewhat annoying thing in this is that given that the rollover for this device is not the actual gps rollover date it must have some logic in there which says something like "if the gps week number is less than 885, the week must have rolled over so add 1024 weeks to the number" implying that (a) they designed it in 1996, (b) they were well aware of the gps rollover but (c) they decided not to care about what would happen in 2016.

You can't *expect* a piece of electronics to still be working after 20 years but I rather think that if the manufacturer knows for a fact that it *won't* work after a certain date, they should declare that when the product is sold. What do the panel thinK?

 

[neil_s]

Thank you all for your info and comments. Indeed, it does seem to be the problem robmcg describes, since my unit has reverted to August 1997, that is 19.6 years back, approximately. There is no feature that allows you to enter date/time from the front panel. I suppose I'm lucky in that the unit is still calculating accurate positions that it feeds on to my Yeoman plotter, although future reliability might be an issue, here. It is a shame, since Furuno stuff is very well built and my GP-30 and it's external antenna are in pristine condition despite their age, as, I'm sure, many others are. I guess I need a new GPS with a simple position display and an output that the Yeoman can read.
Thanks again all!

 

[Orion Jim]

You can't *expect* a piece of electronics to still be working after 20 years but I rather think that if the manufacturer knows for a fact that it *won't* work after a certain date, they should declare that when the product is sold. What do the panel thinK?

I agree, built in obsolescence should be declared at the time of purchase. As a practical matter I hope I have the same problem twelve years from now :encouragement:

 

[Porthandbuoy]

Something I forgot to mention. When I resurrected my old Garmin GPS 45 it had been in storage, sans batteries, for about 4 years. It took longer than a set of AA batteries could last before it calculated a position. It spent the better part of a day 'searching the sky' before it found a date that matched the actual constellation of satellites visible (I presume). I hooked it up to a car battery to achieve this.
Once it had sorted itself out it can now be switched off and on without any problem, other than the date issue. It boots up and locks on in seconds.
So don't assume your old GPS is completely knackered, it might just be lost in time, not space.

 

[neil_s]

I remember that the GPS mouse I got for use with the laptop needed a good morning left out on the grass before it orientated itself. I'll keep the GP-30 this season and see how it gets on. The laptop and Seaclear provide GPS back-up. Switching on regularly seems like a good idea - although, come to think of it, I have moved the boat! Now on the mooring half a mile away!

 

[Supine Being]

I realize that I'm a bit late to this thread, but I am also suffering the same problem with my GP-30. it's great that so many are still going strong, the built in obsolescence doesn't fill me with joy. It's interesting that they don't even seem to know exactly how the problem will manifest itself. Clearly they weren't too worried about ironing this particular kink out - wonder why?

 

[neil_s]

My GP-30 seems to have settled down, now. The little '!' warning at the top-right of the screen no longer appears and the time is correct. The displayed date is steadily moving through August 1997. The lat-long position is accurate. Start up time is unchanged. I guess I can live with it!
I hope your instrument continues to work too!

 

[DaiB]

My Furuno GP80 has had a similar problem for the last couple of years, just date and time wrong but all other functions are fine. I will carry on and live with it but its nice to know what has gone wrong!!