Crossing Time Zones

Best I can suggest is :

http://www.poi-factory.com/node/6652

Will tell you as you are crossing into another time zone.

Yep, the unit will not change the time zone automatically.

It's always confused me that a GPS device can't update the time automatically when crossing a time zone. The MSN feature is nice because it does change the time automatically.
Jen

The GPS unit gets it's time from the GPS satellites which report UTC. The unit then performs an offset of the time based upon the time zone that the user selects.

Based upon your explanation Motorcycle Mama, which I assume is correct, it would seem like they could then create some relatively simple algorithym that changes the time based upon a calculation at designated points on the US map.

Am I nuts here? Why can't they do that?

Are there any Garmins or GPS units on the market that change the time zone as you are driving?

Seems like a cool feature to have and market for those that travel.

Just imagine what would happen if you were traveling very near the "border" of a timezone. And suppose you crossed it and then crossed back a couple of minutes later. The unit would have to be constantly calculating and recalculating.

And then how would the route time be displayed? Suppose you were traveling from Utah to California very near the border. You leave your house in Utah at 1pm MST and 15 minutes later you are in California and it's now 12:15 PST. Would the trip be displayed show negative 45 minutes?

Then suppose you were traveling on a route from Kansas to California and the unit indicated that you would arrive at 3pm. It would potentially be confusing to the user "which" 3pm this would be. Kansas or California? And what day? Today? Tomorrow?

And since this would need to work on every road that crosses a timezone everywhere, it would require a tremendous amount of data. The timezones are not straight lines that easily follow longitude lines. They wiggle in and out all over the place. There are minor variations everywhere.

The software part is probably relatively simple, however, the real world functionality isn't. It's just easier to have it be manually set by the user. Much less confusing overall.

All the kinds (generally not specifically) of variables you mention are basic and typical factors that go into developing any technology of this kind including GPS proper. In addition, we all know the GPS maps are not even close to 100% accurate and we accept that fact as part of the complexity of the technology. Or some would say the result manufacturers choosing not to focus on a specific area/benefit

A room of four engineers (NASA or otherwise) could solve the issues you detailed in a one day session.

So are you stating that there is no GPS on the market today at any price point that will update the time while traveling?

I am just curious because I really do not know.

Thanks MM.

At least one guy has it figured out:

http://www.freepatentsonline.com/6278660.html

I will check around to see what I can find in the real world applications.

Again, the main issues are going to be user related issues not programming related issues.

How many tech support calls a day do you think Garmin would get from users who would be complaining/confused because their route was showing negative 45 minutes?

I'm not aware of any major GPS manufacturer who has this feature. I'm not saying that there aren't any (there most likely are), but I'm not aware of them.

On a side note, BlackBerry phones are specifically programmed NOT to change time zone (as other phone do once they get a signal from the cell towers) since RIM designed them as business devices and business users often prefer to stay on their "home" time rather than changing. You have to manually change the time zone on a BlackBerry.

Not many. The device would still know you're 45 minutes away from your destination. Your current time would be set back or ahead to the "local time" for your location. The ammount of time it would take to travel from point "A" to point "B" wouldn't change. Only your current time and arrival time.

Yes...it would be interesting to find the manufacturers that do have this ability (if at all) and them we could determine how they have overcome the issues you mention and what support if any is needed. I tend to agree with you that most likely this already exist. If it does exist I tend to think the issues you mentioned have been resolved so that technology is user friendly and practical in the field.

If anyone knows whether it exists let me know. In the meantime I will look around.

Thanks again.

As far as I can tell, only the time needs to change, the TOD or Time of Day needs to increment or decrement, the same for the estimated arrival time. If you go back across the time zone, the same two items need to change. There really isn't any "recalculation" needed other than updating the time display - you will still need X minutes to get to where you are going.

It would still take you just as long to get to the destination. If the estimated arrival time when you departed at 1 and it would take 78 minutes to arrive, then the travel time doesn't change unless your scoot can travel faster than time, the arrival hour just changes to match the time zone.

And why is this different than what is displayed now? My Nuvi doesn't show the day of the week as part of the estiated arrival time, it just shows the estimated hour and minute. Is yours different?

Really not such a big deal, for the most part the timezones follow geopolitical boundaries (county/state lines and sometimes city boundaries. The only real fly in the ointment is for those that "opt out" of daylight saving time. The time zone boundary hasn't changed, but the local time may or may not be the same as an adjacent city/county. Yes, it is a lot of data, but if we know where the centerline of a road is and where it intersects the timezone, then changing the clock is not difficult.

Actually, if my cell phone can keep up with the time zones, and their time is also derived from GPS satellites as well, my Nuvi should be able to do the same.

Consider the fact that not even vertical map lines would be enough to determine this. For instance, if I'm in southern Utah at 3pm, then drive south to Arizona, it's now 4pm, as AZ doesn't use DST.

There's also the fact that DST rules change from time to time, which means a forced software update.

What this means to me (a 30 yr software developer) is that it CAN be done, but the effort to keep it updated is NOT worth the user-experience gain.

Well look what I found in no time at all. In the review of the new Garmin 785T I found this sentence:

"With the patented auto time zone feature, these nuvis will automatically adjust your time zone while navigating."

Here is the entire review:

http://gizmodo.com/5042547/garmin-785t-gps-and-friends-free-...

I guess it may not be as difficult in practice after all and Garmin figured it out. It had to be a feature that was always asked about. I am curious to see how it works.

My wife's Acura TSX relies on the factory navigation system to automatically adjust the clock when we cross time zones. Usually it is within 100 yds or so of us passing the "Welcome to " sign. The clock, and the gps, automatically adjust with the time zone change.

I guess someone should asked Honda/Acura how they did it, because I've seen it with my own eyes

I heard the nuvi 7X5T will have this feature.

For me and other truck drivers the way it works is perfict. We have to use the time zone from are home state. So if we need to know the time of wear we are we just look at our cell phones. And for someone on vaction if time is that important then it's not a vaction to me ?????????? Not tring to make anyone mad but??????? Like someone else said here if you leave at 12:00 noon and it says you will get there at 3:00 you know it will take you about 3 hrs. If it took into acount for time chang it might take you 4 hrs and some people may not realize that because of the time change.

Sigh! The very first post in this thread indicated that the time DID change, just not right at the "border". So, it would appear that there is at least one Garmin that does that.

My Magellan does it too. It displays the arrival time in local time for the destination point AND changes time zones.....but not necessarily right at the transition point.

Oh, really?? How did you come to that conclusion?
Mine comes from the cell tower(s). Much simpler to sync that way.

Also it get more complex driving in Indiana where the time changes from county to county depending on whether they use DST or not (IMO, maybe the silliest system ever).

It just isn't that hard to load up the Time Zones POI with a 1 mile alert so you know when you've crossed the line, and can take the 10 seconds to change it at the next opportunity. Are people really in such a huge rush that 10 seconds is an inconvenience to them?

Yup, and that Nav system is a $2000 option, or at least it was in 2003 when I bought my Accord Coupe. My Nuvi cost $300.... I rest my case.

I will have toy grab a 785T toy to go with the 880 and test out all the new features.

The timing for the cell site radios is derived from a GPS antenna. If a site is near a time zone boundary, then the antennae handling your call will determine the time displayed. The GPS timing is what drives not only the clock on the phone, but also keeps track of the time on a call. A time stamp is received when a call is initiated and another when the call terminates. The difference between the two stamps is call duration while the location of the phone and tower determines the time zone.

What leads you to believe that?

It is MUCH cheaper and just as reliable for the cell towers to get their time from the switching host. That IS the way it was done when the cellular network first went up.

And.....since the tower is stationary, what other possible use would there be for a GPS receiver?? The cell site has a built-in clock that is MORE than accurate enough for call duration timing.

I'm sorry but it doesn't make sense to me.

I agree with you. I'm a bus driver and do tours all over the country. It doesn't matter what time as long as I have my starting time of where I started. It would be nice to tell a tour escort what ime but it's easy to figure. I don't know about a lot of features but the lane assist would be nice in cities that I don't drive in a lot. The tour guide feature I could use in very few situations due to tour guides who do that for a living. Bluetooth feature would work for me.

By having the radios sync to a GPS signal, the control timing for handoff is maintained which is extremely important for digital systems. When the original AMPS or analog service was used, timing wasn't that critical, but with the number of units exploding and having to carry many more connections across the same bandwidth, digitizing the signal stream and synchronization between the tower sites and the handsets becomes much more critical.

Most TDMA systems usually carried about 3 to 4 conversations on the same channel through time division multiplexing. Digital systems such as CDMA can carry up to 8 connections across the same channel while iDEN packed up to 12. Since more bandwidth has been made available, the packing has gone down resulting in improved voice quality, but most of the additional bandwidth is used for data services.

Getting all your timing from a central point such as the control point causes more problems due to signal jitter and distortion from the links used to connect the sites. You introduce a microsecond of delay for each mile a signal covers in free space, and the best copper lines only run about 87% of the speed of light, so even more delay is injected depending on the length of the line. Let's not get started on the delay introduced by the connectors.

And GPS antennas are not that expensive. Good low-noise inline amplifiers are the expensive piece.