Navigation ETA Incorrect

There's an on-off setting for Daylight Saving Time under Setup > Clock. Moreover, the time zone can be changed on this same screen.

 

Why would you need to tell a GPS your time zone? Oh, I suppose if you live right near a timezone boundary, you might not want the clock to change every time you go to the grocery store. Is that why?

 

When you set up your Navi, you can tell it what speeds you drive. It automatically sets those speeds (fairly accurately for me), but maybe your driving conditions are far different from the ones they pre-programed.

You can check your owner's manual for more information about setting up your navigation system.

 

GPS transmits UTC time. All GPS units need the ability to convert to local time.

 

I have found out that during the trip, the Nav will adjust the ETA based on your actual speed versus the programmed speed.

 

Really? I've found the opposite - for example, a road that had apparently been misclassified as a "main street" instead of a "freeway" in the system (or perhaps the speed limit had increased – HA! – since their data was collected). As I continued down that road, I would tick off about 3 minutes from the ETA for every 2 minutes of driving, or something in that range.

In any case, the nav is way more accurate than my off-the-cuff estimates, even if I happen to know the driving distance. Usually.

 

Aren't we saying the same thing? When the ETA ticked off 3 minutes for every 2 minutes of driving, isn't this the Nav adjusting the ETA based on actual speed ?

 

I'd say it's not adjusting the ETA based on actual speed at all, other than the secondary effect of recalculating based on the current distance to the destination; say I'm going 60 mph, my destination is 60 miles away, and the Nav thinks the speed limit is 30 mph. It thinks the ETA is 2:00 (instead of 1:00). In one minute, I'm now 59 miles away, and it thinks the ETA is 1:58 (instead of 0:59). In 30 minutes, I'm 30 miles away, and it thinks the ETA is 1:00 (instead of 0:30). It obviously still thinks that the speed limit is 30 mph. It's not doing anything at all with your current speed; it's just that it recalculates continuously based on the distance remaining. It doesn't set the ETA when you start driving and just tick off minutes one-by-one.

If it adjusted the ETA based on actual speed (and not just distance remaining), I'd expect it to figure out that I'm going 60 mph on this road instead of 30, and eventually chop off that extra hour all at once. I don't really expect this intelligence from a GPS, though, perhaps at least partly because there would be too many opportunities to get such an adjustment wrong.

 

I agree that yours is a better explanation in that it is recalculating distances and not adjusting on speed. Either way it is adjusting ETA as you travel.

 

The Toyota Nav system is just not as sophisticated as a Garmin, Tom Tom or Magellan - after all, it only costs 4 times as much. The answer is, of course to manually (there is no other way) turn the Daylight Savings Time off in the winter and on in the Summer, making sure the Time Zone is correct.