time zone anomaly
17 years
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We just did a trip from NC to MN. While still in NC, I used Mapsource to input into my Garmin 765t, the route I wanted to take. The Garmin came up with 1201 miles in 17hrs 42 minutes. Using 14 waypoints to peg the route so it isnt recalculated when sent to the unit. While here in Cottage Grove, MN, I used Mapsource to config the same route back to NC. It showed 1209 miles in 19hrs 55 minutes. I dont think I overlooked anything. I sratched my head for a while before coming to the conclusion it must be the timezone change that made the difference. Has anyone else had timezone issues? Crossing time zones is the only reason I can think of for the almost 2 hour difference in travel times. Am I correct in my analysis? Or could I have overlooked a terrible flub up? We been so buzy, I havent had the time to critique it that closely.
Time Zone Difference
I shouldn't think that time zones would have anything to do with it. Mapsource should be calculating driving time - not clock times. We know that the Garmins don't change time when crossing into other time zones, so ETA should be on Eastern Time, even though you were travelling into the Central Time Zone. I've seen differences in the drive times between going and coming back in Mapsource, but only a few minutes either way - never as much as two hours. Are you sure the waypoints were exactly the same both ways? Very strange, if so.
Waypoints on divided lane roads?
Did you use the exact same waypoints when you reversed your route? If so were any of them on the wrong lane of divided highways causing some backtracking? Still, it doesn't seem like that would cause a 2 hour difference.
@spullis - some Garmins change time when crossing zones ... my 755T does.
Alan - Android Auto, DriveLuxe 51LMT-S, DriveLuxe 50LMTHD, Nuvi 3597LMTHD, Oregon 550T, Nuvi 855, Nuvi 755T, Lowrance Endura Sierra, Bosch Nyon
highway lanes
Yes, I was very careful about traffic lanes. I looked at the Garmin route back to NC. It looked like the same route coing back as coming up. This is strange, the differnece in time travels. If time zone has nothing to do with it. I do wonder what is going wrong. I did not use the same exact waypoints. Just enough, and in the right places to keep the gps from recalculating a different route. At any rate, thank God, I have the paper maps too!
Unless you are the lead sled dog, the view never changes. I is retard... every day is Saturday! I still use the Garmin 3590 LMT even tho I upgraded to the Garmin 61 LMT. Bigger screen is not always better in my opinion.
765t did change time
We know that the Garmins don't change time when crossing into other time zones, so ETA should be on Eastern Time, even though you were travelling into the Central Time Zone.
My Garmin did change time when we crossed into Wisconsin. Or maybe it was Illinois. Not sure which state, but it did change the time back an hour just as we crossed the border.
Unless you are the lead sled dog, the view never changes. I is retard... every day is Saturday! I still use the Garmin 3590 LMT even tho I upgraded to the Garmin 61 LMT. Bigger screen is not always better in my opinion.
Units with auto time zone change...
@spullis - some Garmins change time when crossing zones ... my 755T does.
Yes, the newer nuvis (beginning I believe with the 2x5 series) automatically sets the unit's time according to which timezone you're currently in. These units use a time zone boundary map specifically meant for this purpose. The timezone map (~582kb depending on the version) is in the x:\Garmin folder on the nuvi drive and is named gmaptz.img.
nuvi 760, nuvi 765T, nuvi 855, nuvi 3790LMT, nuvi 3490LMT - SoCal area
Oh, Okay
Yes, the newer nuvis (beginning I believe with the 2x5 series) automatically sets the unit's time according to which timezone you're currently in. These units use a time zone boundary map specifically meant for this purpose. The timezone map (~582kb depending on the version) is in the x:\Garmin folder on the nuvi drive and is named gmaptz.img.
Well that would make sense then. So the actual travel time calculated by the garmin was about 18 hours and 50 minutes. Going from NC to MN it subtracted an hour for the time change, and from MN to NC it added an hour. That is how you got the two hour variance.
My unit (nuvi 760) doesn't do that, so I am just taking a stab at the math.
=== Even a broken clock is right twice a day.
That's exactly right
Well that would make sense then. So the actual travel time calculated by the garmin was about 18 hours and 50 minutes. Going from NC to MN it subtracted an hour for the time change, and from MN to NC it added an hour. That is how you got the two hour variance.
My unit (nuvi 760) doesn't do that, so I am just taking a stab at the math.
Your math is correct. The duration of travel each way would be the same, but the calculated ETA would be +1 hour going one way and -1 hour going the other, thus the 2 hour difference.
"There's no substitute for local knowledge" nüvi 750, nüvi 3597
timezone change
I do hope that the timezone crossing created the difference in travel time. Sounds logical, anyways. Cant see any other reason for it. I havent seen it documented anywhere. Guess it depends on which gps you have. I witnessed the arrival time hour roll back when we crossed over into Illinois. I thought the Garmin would be smart enough to take the timezone time change into account.
Unless you are the lead sled dog, the view never changes. I is retard... every day is Saturday! I still use the Garmin 3590 LMT even tho I upgraded to the Garmin 61 LMT. Bigger screen is not always better in my opinion.
Why not just use "Invert Route"?
... It looked like the same route coing back as coming up. This is strange, the differnece in time travels. If time zone has nothing to do with it. I do wonder what is going wrong. I did not use the same exact waypoints. Just enough, and in the right places to keep the gps from recalculating a different route. At any rate, thank God, I have the paper maps too!
What happens if you select your route in MapSource and then select Invert Route? This should give you the exact same route with the identical waypoints, just reversed.
I didnt know
... It looked like the same route coing back as coming up. This is strange, the differnece in time travels. If time zone has nothing to do with it. I do wonder what is going wrong. I did not use the same exact waypoints. Just enough, and in the right places to keep the gps from recalculating a different route. At any rate, thank God, I have the paper maps too!
What happens if you select your route in MapSource and then select Invert Route? This should give you the exact same route with the identical waypoints, just reversed.
I didnt know you could invert the route. I will go looking for that option and do that. Just started using Mapsource about 3 weeks ago. Thanks for the tip!
Unless you are the lead sled dog, the view never changes. I is retard... every day is Saturday! I still use the Garmin 3590 LMT even tho I upgraded to the Garmin 61 LMT. Bigger screen is not always better in my opinion.
While taking time zone
While taking time zone changes into account is nice to determine one's local ETA, shouldn't the GPSr tell you how long the actual travel time is? That would be like saying that it takes 3 hours to fly from NYC to LA and 9 hours to fly from LA to NYC: what I really want to know is how long the actual flight is (6 hours, although the LA-NYC actually about an hour SHORTER than NYC-LA due to prevailing winds).
-Dave
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Airlines always display arrival times in the destination's time zone. It just makes sense to do it that way.
If you are speaking with a party at the destination and tell them the navigator says you'll be there at 12:00, it would be wrong.
For whatever reason, Garmin chooses to display ETA based on the current time zone. Very confusing, the first time you encounter it.
The ETA will change as you cross the line between the zones.
I've wondered why . . . and also wondered whether whether there should be an asterix or something (perhaps posting the time zone after the time or flipping between the current zime zone and the destination time zone?) to indicate that there is a minor issue for consideration when this happens.
Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T