Modern Vespa

I should know this, but I don't. Everyone here is pretty smart so, hope you can help. I have a Garmin GPS. Why does it not take the same route from your destination as the one it picked up for the trip there. Granted, the roads, exits will be different but basic route still the same. Today, my GPS took me through back roads and all over the place. The trip back was four land all the way from our destination to home. I did not make any changes in the GPS and maps are fairly up-dated. thanks.

I have no idea why, and I know nothing of the algorithms used by the routing engines.

It's happened to me, too. I recently made an out-of-state trip and later, when I was leaving to return home, was surprised to hear the GPS direct me to turn left out of the parking lot when I had arrived from the other direction.

I did, but out of sheer curiosity, I went down the street a bit, turned around and found that after a very short distance, Samantha (my GPS) was just as happy if I went that way...and didn't tell me to turn around.

I'm guessing that my destination was in the very center of two equally good, but different options.

Of course, if the two choices were radically different time-wise, then...

I dunno.

Mine likes to take me around the block to get to destination .instead of a simple left turn in.haha

The GPS uses a "logic" to figure a route. Typically, it's the shortest time, based upon the map data base's speed limit info, as long as you have not entered "modifiers", usch as "avoid freeways", "scenic route", etc. It then executes this logic starting from your current position, which may show Road A more readily evident to go in a given direction than in the reverse. Thus, the common phenomenon of the GPS recalculating a route you more commonly expect if you ignore the original instruction and start off in the direction you think is preferable. The incredible accuracy of the current GPS units leads them to "split hairs" more finely than we do in our heads.

If you were to compare the estimated time/distance between the outbound and return routes, they probably would be very similar.

Our GPS likes to drag us through downtown Denver every time.

We don't live in Denver!!!

Both of mine do this, but I see it as a perk. It's a reason to spend more time riding/driving, aswell as a chance to see some new sites which you may never of seen if you wasn't to use a sat-nav.

I'm just too dependent on GPS. Since my work involves travel, I can't count how many times it's steered me so wrong. Sort of missing the good old days when I carried an atlas. Picked up the rental car, proceeded to town and stopped at a gas station and would ask for directions or buy a 6' x 6' street map and unfold it on the hood. If that didn't work, the a pay phone would

On my automobiles, you can choose between shortest route,avoid tolls, quickest route etc. if your GPS has traffic, icould be avoiding traffic back ups? I've never owned a handheld because I always get it navigation in my cars.

Don't you have options of which route it prefers?

All too often, a driver with a GPS really doesn't know where they are. The GPS is simply telling them where to go.

As was said, the algorithms are pretty complex. Image what it takes for a computer to pick the shortest or fastest path. It makes you appreciate how amazing the human mind is.

Other than the "avoid" or setting issues even a single one way street can set it off. Remember, it's "doing it's best" when it pics a route. That's tough for us to think about with a a machine. Often it sets a limit on how long it will try to optimize a route and give you it's best guess. Over the years as the SW geeks continue to play with the algorithms they get better, but sometimes a bit more eccentric. The new ones are really just amazing!

Also, user error is a big cause of misdirection. We tend not to admit that we've selected "W 7th st" vs "E 7th st"!

If I decide to go a different way and do not reset the GPS it insists on taking the shortest way back to its original route. If I cancel the trip and re-enter it, the GPS is quite happy with the new route.

I read somewhere that the GPS draws a straight line between waypoints and then finds the best-fit roads to that line, subject to the 'avoids'.


Don't you just love it when you take a newly-built road that is not in the maps? "Recalculating". "Please drive to highlighted route". I swear its voice rises an octave the longer I am in the middle of nowhere.

GPS with attitude!

Check your units settings under "navigation". If it's set for "fastest time" that may explain it taking traffic, time of day, and left turn count into the calculation it makes.