How to determine my 680's accuracy?

To find accuracy, touch the signal strength (the bars) icon on the main menu.

I had the same issue with my 'car' being on the wrong road for a bit, it was either because of sun flairs (i am not joking) or the refresh rate was really bad (and I had to return the unit)

I've seen the same problem on 680 once or twice or roads that are close and parallel to each other. The GPS had me on the highway while I was driving on the feeder road. The accuracy of the GPS varies depending on the number of satellites it's locked on to and their position in the sky. The more satellites it sees and the more distributed they are, the better the accuracy. Your location on earth (what the GPS determines) and the road your driving on (GPS mapping software) don't always match. This can cause problems when your driving on two roads close to each other. The real world position the GPS detects (with errors) could have your car closer to the other parallel road your car is not driving on. So as not to show your car driving down the median (what good is a auto GPS if it doesn't show you driving on the road), the GPS snaps your car's visual position on the GPS display to the nearest road that matches your direction of travel. When accuracy improves, you could see your GPS map suddenly change and show your back on the right road. That's just the way GPS software works.

Is that San Francisco style "flair" or flare as in "road flare".

Fine a GPS Geodetic benchmark near you as reference.

http://www.ngs.noaa.gov/GEOID/GPSonBM99/gpsbm99.html

See told you that I was an idiot, didn't even catch that!

No problemo... Just funnin' with ya.

But, I do have to comment on your avatar.

[big gay al] That's a thooper color shirt you have on there! [/big gay al]

When I checked the accuracy per the instructions to touch the signal strength bar, I got readings that seemed darn good compared to others that I've seen posted. As close as 12 feet up to 19 feet.

This seems very accurate to me, based on what I've read, so what would account for the ongoing problem of seeing myself being shown on a parallel road that was at least eight traffic lanes plus another 20-30 feet away from my position???

As I said before, this never happened with the 660 that I bought in early October.

Any ideas what I should do next? I'm wondering what Garmin tech support will tell me when I call on Monday. Suggestions on how to approach them?

Thanks again for your thoughts,

GeneL

Can you elaborate a little on this, please?

Well if it isn't the receiver it only seems to reason that it is the map image isn't calibrated correctly for the proper lat-lon data. Personally I wouldn't worry about it since it is only for a short distance. I see the same issue with a feeder road especially when the route it wants me to take say is the freeway and I jump off on the feeder.

Had a similar thing happen on a business trip up to Nova Scotia. In the middle of BFE, my 2720 had me a few hundred feet to the right of the highway. Lasted about 10 minutes. I read somewhere that in rural areas the mapping companies often don't actually drive the roads to collect GPS data points. Sometimes, they use a touch screen computer and trace the roads from satellite imagery. I figure somebody's pen/stylus just slipped.

Any fix for a map calibration problem?

My obsession with this "small" accuracy problem is based on my previous 660's not having this issue??? This makes me wonder if it's a model to model issue or, perhaps, due to different production runs. I purchased the 660 in mid October and the 660 a couple of weeks ago.

Once again, thanks for your thoughts.

GeneL

I noticed this a fair bit on the Nuvi 250W & Nuvi 200. This usually happens when I do not have a destination set and just have "view map" displayed. I take an exit off the highway and am about 100-200 meters from the highway moving away in a diagonal (not parallel) fashion before the unit snaps me from the highway onto the exit road that I actually am on.

I think this is a software quirk from Garmin as the unit is pretty accurate (4 m accuracy on this highway).

I also noticed that the unit is very accurate and can actually place your car on the actual side of a the street it is on. I tested this briefly by turning the navigation to off road. My car snapped to the right side of the street I was parked on. Changed it back to fastest router and my car snapped to the middle of the road. So it has something to do with the way Garmin has programmed fastest route and off road behavior.

Another quirk I noticed was when I drive to this particular destination on a dead end street. I am told "arriving at destination on left". I head to the dead end of the street, make a U-turn and come up to the destination. The unit AGAIN repeats "arriving at destination on LEFT" instead of RIGHT. Anyone else notice this kind of behavior?

I cannot view buffettck's profile to see how long he has been a member. Does that mean his post caused his suspension?

Those are reference points to use if one decided to see how accurate their GPSr is. Find one of those locations and if it is within 3 meters with your GPS then your receiver is working as advertised.

It's easier to use a mapping GPS than an auto GPs. Because a mapping GPS can tell you how far you are from a coordinate in feet or meter.

This community is built on common respect for each other, if you continually show that you are not able to conduct yourself in a respectful manor, you will be shown the door. I have no tolerance for this type of conduct in a society that is built on respect, civility and honor amongst ourselves. He is not here any more for a reason.

Miss POI

Very well said Miss POI

My 660 looses me, once in a while, but it gets back on track in a very short period of time. It doesn't happen very often. I just chalk it up to the lag time needed for triangulation.

There have been times when I would start up the gps in my car and if I’m standing still the gps would show me on the wrong side of the street. But this is something that always cleared up for me once I started to move.

GeneL have you tried to update the unit at all via the Webupdater? Also, have you tried to reset the unit?

Bravo!

I wondered what happened to him, will reserve my comments tho.

While all GPSr units will exhibit a degree of inaccuracy that can be estimated by an "accuracy" indicator, it does not take into effect software decisions made by the routing software. To account for accuracy fluctuations, most if not all GPSr units have a "snap to road" decision feature in their software. Meaning that if the calculations show you as driving 20 feet off but parallel to a road, the software routing logic will assume that you are actually ON the road and that it's reception calculations are off by 20 feet. When two roads are close to and parallel to each other, it is not uncommon to have the unit occasionally make the wrong decision about which road you are actually driving on. And once that "decision" is made, how easily the unit will give up and decide that you are actually on the other road is dependent on the programming logic, as well as the accuracy of the unit. Keep in mind that the map data may actually show the roads as being closer than they really are. This same decision logic is applied when it decides you are off-route and it needs to recalculate.

Well said and well executed, Miss POI. Intolerance of protected class or otherwise should never be tolerated in a public forum.

Johnc thanks for the explanation. I did understand part of the underlying logic and your explanation makes it even clearer. From a more detailed discussion on another forum it seems that these "problems" do NOT exist on some of the earlier Garmin models. So it would be nice to have the accuracy of the old units in the newer ones without losing something else.

I do find it disconcerting when I am driving downtown (not an urban canyon here) that it thinks I am on its mapped route when I am actually on a parallel street. With the number of one way streets here it would be foolish to follow the GPS instructions blindly - but then again what if you are in an unfamiliar city and the unit goofs up this way?

My own experience is that my Nuvi is more accurate in this regard than an older unit that I had several years ago. This was a pre SiRF-III GPSr which at times showed my pointer as being 50-100 feet from where I actually was. Obviously, that older unit did not have as accurate a receiver and the software was not as aggressive at "snapping" my pointer to the nearest road.

I found it to be very disconcerting to watch my pointer "wander" off the road at times. But I have to agree that it is even more disconcerting to have it suddenly decide you have left the route and it begins issuing re-routing directions. I have had less of this with my Nuvi than with that older system. Fortunately, in both cases it is/was pretty rare.

My first GPSr so I have nothing to compare with - only complain! But I see your point and understand where the trade off is being made.

If I notice I am not being shown on the correct street and I am not comfortable with it, I STOP the route and set my destination again. It takes 6 quick clicks to stop my current routing get my destination set up again.

It seems from some comparisons that the Magellan's don't exhibit this behavior. So maybe they're not as aggressive in "snap to road" as the Nuvi is.

Small quirks on the Nuvi that show up occasionally and can live with them. Just hoping there could be a combination of settings or solution to overcome this. Maybe an update from Garmin as more people bring it to their notice.