How does TT know which day it is?

navtrav

I have Go 730, latest maps & software.

The IQ route planning is highly trumpeted as a way to avoid rush-hour blackspots etc.

But, as there is no calendar in the thing, how does it know when I set off whether it's a sleepy Sunday morning or a hectic Monday morning?

Yes, it can see the time, although my internal clock seems to keep re-setting itself to 12am (another topic!).

So I try 'advance planning'. And yes, you can eventually menu your way to choosing a day. But up pops this ludicrous calendar that only shows 1970-71. While I'd really like to time travel back to then, it is totally irrelevant to my journey today.

So my conclusion is that the IQ planner has a very low IQ. Please tell me I'm wrong and show me the error of my ways. Advice gratefully received.

Tim

PS I did a search in TT forums on IQ but found nothing noting this glaring TT con.

norm2002 · Posted: Mon Dec 01, 2008 11:49 am Post subject:

I believe it is just that, when the TT gets a full GPS fix, it gets the time AND DATE from the satellites.

After a hard reset you may have to tell it the offset from the standard time it uses. Not sure what this is as it seems to be something like PST on mine.

navtrav · Posted: Mon Dec 01, 2008 11:59 am Post subject:

Thanks norm2002. So I guess the satellites know which time zone (eg Paris/London?) that I'm in by the fix on my position and thus correct my clock? Is TT software this sophisticated?

garcor · Posted: Mon Dec 01, 2008 12:04 pm Post subject:

Anita

navtrav · Posted: Mon Dec 01, 2008 12:31 pm Post subject:

Thank you Anita. It seems I'll have to phone TT. (Help lines are my worst nightmare.) Even with a satellite fix I still get the 1970 calendar,

Mind you, having to get a gps fix does negate the value of advance planning as one is very likely to be doing that in a building before setting off.

norm2002 · Posted: Mon Dec 01, 2008 12:35 pm Post subject:

matthewj · Frequent Visitor Joined: Apr 03, 2006 Posts: 751

navtrav · Posted: Mon Dec 01, 2008 2:19 pm Post subject:

Thank you everyone. Sorry for late response - blame Virgin Media loss of signal!

Yes, I take it back. Ten minutes after getting the gps fix I was able to get an up-to-date calendar up.

So what you're saying Matthewj, is you still need to reset the clock to get the right 'offset' if you change time zone, which I guess for us Europeans isn't too hard a chore!

I think my TT's reverting to 12am is due to the battery going flat, which I find with this newer model it does very quickly if it's not used for a week or so. My old Go lasted for ages.

mattcu · Occasional Visitor Joined: Apr 11, 2008 Posts: 25

If it's any consolation, I think the time zone offset is likely to be simply a cosmetic measure for your benefit. I'd bet that all IQ2 data would be referenced according to the UTC time, regardless of the country about which that data is stored.

This is certainly how aviation and nautical GPS-derived guidance systems work. Especially so because the two GPS constellations (Navstar, the American one and the one which most western 'GPS' systems reference, and GLONASS, the Russian one) emit their time signal in UTC format.

I'd bet that TomTom performs its calculations based on UTC - the time the satellites emit, and the time that IQ2 data is (in my speculative opinion) likely referenced to.

For our purposes, UTC is essentially Greenwich Mean Time.

This does, however, introduce one hypothetical questions how does IQ2 adjust the various IQ2 route costs at the start and end of British Summer Time? I'd wager that it probably doesn't...

I also suspect that Advanced Planning tool is somewhat limited. To be perfect, it would rely on the user having the correct time offset entered (for adjusting the 'start journey at...' time to UTC) or will have to approximate the time zone based on the longitude of the start position. Roughly, time zones change every 15° of longitude but this is only an approximation.

As with many areas, I'd love to know how TT actually do it, and how (or even if) they solve these problems.

Calomax · Posted: Tue Dec 02, 2008 9:55 am Post subject:

navtrav wrote

Skippy

MrT · Posted: Thu Mar 12, 2009 12:41 pm Post subject:

This morning I updated the 530 from Home and it reset the clock and calendar (with a full battery) until it received a satellite signal. The updates were only the usual Cameras, Mapshare and GPS Quickfix.
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DennisN · Posted: Fri Mar 13, 2009 1:37 am Post subject:

What a load of cobblers!

Question - How does TT know which day it is? Answer - TT doesn't know which day it is! TT doesn't know its xx from its yy (substitute your own ideas)!

TT doesn't know an awful lot of stuff, like how to make my two devices do what TT tells me to expect of them.
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Dennis

If it tastes good - it's fattening.

Two of them are obesiting!!

GerryC · Posted: Fri Mar 13, 2009 11:57 am Post subject:

It's OK Dennis, the TomTom doesn't have a clue what date/time it is or even where it is until the satellites tell it.

Of course, if your devices show different times when sitting next to each other, then [insert own imagination here].
Out of here

Seriously, if I leave mine without a signal for a few days, even when charged, it reset the time to 12:00. I believe this is due to a timeout to prevent the device holding potentially inaccurate data. Once you get a signal lock, it's back to normal.
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