Is my Garmin guessing?

It's called road lock. Garmins have done this for years. It locks the unit to the line that represents the road on the map. I always felt it was a coverup for bad position or map data. It makes the track look nice on the map software.

I would have thought that the high dollar units would have a way to turn it off.

If you want a better picture of how inaccurate the device is then put it in pedestrian or off-road mode. This will turn off the snap to road feature.

Yeah, that feature is annoying especially if you're traveling on a road parallel to the one it shows you on.

Some of the units do.

Nuvis aren't "high dollar units", they are "high volume units". The 276 series 'are' (in quotes because most of the series has been discontinued) high dollar units that have the feature (and a GREAT display), but the 640 is a current unit that probbaly does it too (haven't checked). Units with portability also can run in offroad mode.

I haven't played with the 1200, 1300 & 1400 series but at least some of them support a pedestrian mode with ought to switch off the lock to road feature (and probably also breaks the routing - hard to walk on a highway - but that's another story)

Who makes the 276 or 640, and having stated the Nuvi's arn't a "high dolar" setup, are the 276 or 640 even Garmin products (outside of the Nuvi line)?

What is the price range of high dollar units?

And how much are the 276 or 640 in price?

I thought Nuvis were kinda expensive.

I had a 885T that never did that.

M y Garmin 250W does the same, but after I have past the exit for a 50 or 100 feets it will say recalculation and so on, and if I take an exit I am not suppose to it will do the same thing.....

Anything in the Nuvi 7xx and above is high dollar to me.

My unit will show me going off the highway and keeps telling me to turn to get me back on the route on the GPS?
David

I have a Lowrance Iway 250C that always knows if I am on the Interstate or the access road.

The Nuvi 265WT stays locked on the Interstate unless the access road is included in the route.

These options will not be practical for navigation for a car. The route for pedestrian is not the same as that selected for a car. It won't take you on an Interstate. Off road is straight line navigation between two points, no roads are taken into account.

I would think that Garmin would release a firmware update to fix the issue.

I wouldn't hold my breath.

Is there a way to get driving turn by turn directions, but be in pedestrian mode?

Basically, I'd like to be able to get turn by turn directions w/ out the road lock.

Any ideas?

You won't like the route that it takes or the ETA and I think you will still have road lock. I haven't tried it on the road.

The streetpilot series and specifically the c550 will lead you on and off the ramps and along service roads with no problems ever. The Nuvi's locked on a interstate like to stay locked right on the interstate even when off of it when your in eye sight.

The snap-to-road feature is an absolutely necessity for use in an automobile. Without it, the gps would show you 30 feet off the right side of the road and then 30 feet off the left side -- since the vehicle is always shown at the same point on the screen, the map would be jumping all over the place. Since you are not known to be on any particular road at that point, the unit couldn't route you.

If you always have a problem with the unit showing you on a parallel road at a specific location, I'd suspect poor map data. If it is all over, I'd ask a friend to allow you to borrow his unit alongside yours to see if you have a defective unit. If you mentioned the accuracy you are achieving, I didn't see it, but it could even be your vehicle -- coating on windshield or placement within a hybrid have been reported as causes of weak reception.

That's not true. The Lowrance Iway 250C does not have road lock and has no problem routing turn by turn. If you zoom in there are times that the track/trail is not on the line of the "road". Most times the track will be in the appropriate lane.

It doesn't have the other problems you describe.

Does the owners' manual for the 250C say, "This unit does not have a snap-to-road feature"? If not, and you are basing your assumption on the bread crumb trail, I would argue that doesn't prove the lack of snap-to-road. Without snap-to-road, how would the unit ever know whether to do a recalculation of a route -- it would see you as having left the route half the time.

Your problem is not the feature, it is inaccuracy of the unit caused by an unknown. If the unit is now snapping you to the wrong road it is because the calculated coordinates are closer to that road than the actual. What good would it be to have the vehicle icon show up half way between the two streets.

You can believe what you want to believe.

Pedestrian mode will disregard one-way streets, no left/no right turn intersections and will not take you along highways, since it thinks you are walking. That's all it really does. It still has you follow roads, since that's where the sidewalks are.

The only thing that turns off road lock is off-road mode, but then that completely ignores the roads altogether. If you want turn by turn routing, we're stuck with road lock. In general, it's a very good thing. Annoying when it happens to lock on an adjacent road, that's for sure. This is not unique to Garmins, of course. I have had it happen with other systems, too.

if you turn on pedestrian mode will it still follow the highways? guess i could just experiment with this.

My 360 doesn't have this issue. And it's pretty accurate (within 5 feet).

Highways as in Interstates and expressways, no. Streets, yes.

I agree that snap to road is a necessity, but there should be a limit. These are really big roads, so when I'm on the right hand side of the service road, I'm the better part of 100ft or more from the right side of the freeway. It should be smart enough to figure that out, if its getting fast enough and accurate fixes.

Someone else made the comment about high dollar units, and this is not a NUVI, but a garmin built into Kenwood in dash. Although the unit is High dollar (a grand +) one would expect the NAV to be sophisticated as well, but I'm not so sure that thats the case.

Since its built in it doesn't have pedestrian mode, but it does have "Off road", so I'll try that to see just how far off the fixes are.

Do you have the same problem while using the service drive on the other side? I am just thinking you may be finding a bit of map inaccuracy.

Could just be a margin of error to take into account very wide expressways (six, seven lanes per side) and you're just within the margin of error). Otherwise it'd have you off the road when you were still on it.

Yes it has the same errors either side of the expressway. Actually it does the same on or off the service road. In other words if I exit it keeps me on the freeway, if I enter the freeway it keeps me on service road

The unit only knows where you WERE. Not so much where you are going. It also has to have an allowance for variances in accuracy (a whole different topic in it's self) which could be anywhere from 10 to 90 feet regardless of who made the device. Don't forget, the distance of the roads may be to scale, but I haven't seen a map yet where the WIDTH of the road is to scale. They all appear the same wether the road is 10 feet wide or 50 feet wide...

I think I'll take my TomTom out for a drive. I dont usualy use it on this section of freeway since its in my wife's car. I'm pretty sure its not going to suffer the same error. But lets see

I find that if I take the service road or exit ramp, the Nuvi will show me on the road. It is only after the exit ramp veers away from the road that it will begin "recalculating."

Just an observation here from my trip into the Adirondack mountains with my 765T last week-

We rented a boat one of the days and were on several lakes all day. When I first put it in the boat, it tried to show me we were on the closest road, but corrected itself after a short time away from the shore. On the first stop at a cabin dock way down the lake, I put it in pedestrian mode and it did the same thing but corrected itself more quickly (almost immediately).

Sounds like a reasonable software algorithm to me, although I could see having no "road snap" at all in ped mode or tighter tolerances in driving mode if it always shows the wrong road when they are close (I haven't seen that on my 200W or 765T w/latest firmware).

On my Garmin 350 I have WAAS (Wide Area Augmentation System) turned on. It makes a big difference in the accuracy. Might want to give that a try. It's under settings/system settings/WAAS on my unit.

It would be a nice option (from the manufacturer) to allow for the user to select from degrees of accuracy for the 'snap to road' feature, like... "low" for in town, or "high" for the freeway, for instance.

It's all to do about accuracy. The circle you see will show you the error range in some units. If you drive and turn the gps on, the unit will have a hard time to calculate your location as start point and compound the problem as it calculates your location. The only thing you can do IMO is to sit in park and turn unit on and wait until it completes calculation of your location. You can also look at how many sats the unit locked on. The more satellites, the more accurate the location. My Garmin had a hard time finding it self at the Mall Of America LOL. I find that you should use the GPS only if you are totally lost or you have coordinates of location you are looking for. Service road I can live with but when it tries to rout you in the wrong direction, way out of the way when you can see where you should be going that's my limit. I don't trust my Garmin anymore. Maybe time for different unit.

The problem does occur but it seems it is so rare that it is not a big problem

Many of us experienced a certain "Wow Factor" when we had our 1st encounter with a GPSr. This thing knew were you were, where you were going and displayed this really cool map of what's out in front of the windshield. Wow!

Then we discovered flaws and inconsistencies. Some were amusing, most not a very big deal, and rarely one that you only survived because you were paying attention to the road and not trusting the GPSr 100%.

There are many variables that determine what you see. The design of the receiver, the antenna and its placement are a big factor. The constellation of the satellites is ever changing and there are times when the calculated position will vary by 10-20 meters or more only because of the relative positions of the satellites. Some models display a circle as mentioned before, and this circle will shrink and grow to illustrate the estimated position error. The amount of clear sky from horizon to horizon is important; in a car its view through the windshield is adequate but not the best it could be. More money can fix some of this, but do you want a comma in the price tag? With continual advances, models to come can be better at an affordable price. We see this all the time.

Until a recent update to the maps, there was a town I passed through were the streets were skewed by nearly a whole block. The GPS knew where it was, the map was wrong. Maps are constantly being updated so this can also get better in the future.

In cities, the signals received from the satellites are sometimes multiplied and delayed by the reflections from large buildings and this skews the results. Other signals that would have been blocked by a building may be received after reflecting off one or more buildings. Have you been in carnival with a house of mirrors lately and realized that exit wasn't where it appeared? If you recall rabbit ears and old TVs you are familiar with ghosts. This was caused by the same multipath reflections. Software might be able to compensate for some of this, but there are limits.

If you look at Google Earth and browse around a bit you will notice that many times the street level cameras are dead-on the roadway, but sometimes they are tracking down the middle of someone's front yard! When that happens, it seems that everything in that area is off that same amount so it is possible that the patchwork of satellite images were pasted off-center. Occasionally you will see where the images were spliced and the road is offset between the two images. Other digital maps seem to have similar issues, and these issues can be fixed if the publisher wants to expend the resources to do it.

The road lock feature tries to compensate for many of these problems, but there will be times when you're on the access road while it says you're on the freeway and Jill is nagging you to get off the freeway... Is it one or more of the above problems, or do you have a GPSr that is not up to the task? Chances are good that you have a friend who will loan you theirs and then you might be able to figure out what's amiss.

When you realize that the GPSr is receiving signals from satellites each moving at 7,000 mph that are in orbit more than 12,000 miles above the earth and the GPSr has to receive, decode and measure the time difference from each signal, it is amazing that any of this works as well as it does. Along with the PC, the GPSr is probably the most complex system many of us ever touch.

On my 680, as it got older (i.e. over a year old!!!) it started routing me off the freeway, onto the ramp, then immediately told me to get back on the freeway. Very annoying. It started doing this more and more often. It was especially bad in the San Francisco area where it would have me get off the highway a couple of exits early in heavy traffic. I would work my way over, exit, thinking that it was routing me on a 'better' shortcut, then it immediately instructed me to reenter the highway... causing me to fall back 1/2 mile or so in traffic. Also, I would sometimes then need to cross 3-4 lanes of heavy traffic to get to the left-hand exit I originally was heading toward. My 765T has only done this once, but I have not been in the same places.

However, the 765T has recalculated my route a number of times saying 'severe traffic ahead, recalculating.' Most of the time I have trusted it, which has been a mistake. (Since the MSN traffic seems to have no concept of 'correct' delay times, the auto-recalculation of a route based on traffic is usually not time-saving.)

I keep my avoidances set to include traffic, so that I am made aware of the traffic situation, but I need to be more selective about whether to accept the suggested new route or simply ignore it and let the unit recalculate my route again after I ignore the 'detour.' The problem is that it is sometimes impossible to distinguish a valid exit suggestion from one based solely on traffic conditions, unless the 'severe traffic' message is given.

If anyone has any suggestions, I would greatly appreciate hearing about them.

Is there any chance you have your unit set for Shortest instead of Fastest? If it got changed, that might explain the odd routing pattern that looks for the shortest distance.

I agree. When you come up on a line of brake lights, you don't know if that line extends 1/2 mile or 20 miles. If the backup is extensive, the alternate routes may already be clogged and a route switch might be worse. With the traffic data enabled (if it's current) you have some idea of the extent of the backup and can see if it's getting better or worse as the delay value changes.

Thanks... I will have to try that too.... It is very annoying especially when you are traveling somewhere you have never been before with service roads!

A minor thing - as long as you know where you are it isn't an issue.

BTW - I like your quote at the bottom of your post.

I look to economic GPS units to get me from point A to B. Although high end units appeal to me, I can't justify the cost for what I need and intend to use. I recently moved from a 3100 Maestro to Nuvi 255WT. Yes, I did say economic units. I really like the Nuvi, but I miss alot of the suttle differences in the Maestro.

Back to the thread, the Maestro did "snap to road" but not as agressively as the Nuvi. I have noticed that the Nuvi, on some interstate exits/ramps, will stay on the current road for a bit longer before snapping to the ramp. Often some distance after the start of the ramp, on the screen. The Maestro would almost immediately start showing the icon at the start of the ramp.

I guess it can be for cosmetic purposes, to show the car icon nicely on the road. But I think it's more to hide the faults in mapping and GPS unit coordinate lock. The earlier Garmin III+ units with MapSource often showed track logs always in the same place after multiple passes on the same road indicating a very accurate and consistant lat/long; but the "bread crumb" trail was not on the road. Just proving to me that not all maps are driven tested, but improvised with drawings.

Honestly speaking, some Product Manager probably had the decision to either spend millions getting the MAP/unit fixed right - or spend a few thousand and internal development hours dumbing down the unit's firmware. The consumer feels they are being served with updated firmware with enhancements like "improved onscreen mapping"; and the ProductManager takes many KUDOs for saving the company tons of money. Besides, the manufacturer needs to keep some distance between higher priced models.

Anyway, having a GPS unit in the cockpit with me is better than a GoogleMap and directions printout; or nothing at all. Having an up2date map with POI db just adds icing to the cake. Always keep a sense of where you want to go, and use the GPS to aid you. GPS are not full proof, only put 100% faith in them when you absolutely have no idea "How to get back to the interstate".

Well I finally remembered to take my TomTom out for a drive on the same freeway that I use to work. What a difference, It picked up exactly where I was, and even showed me on the on or off ramp. So I guess it just comes down to the accuracy of the unit, or the sampling rate.

I'm not sure how it is on other Garmins but on my nuvi 205, it entirely depends on what mode the GPS is in as to whether it snaps to road (route) or not.

When I have it giving directions to a location, it does the snap to route thing but when I am just viewing the map, it doesn't snap to any route and will show exactly where I am.

I actually like it functioning in this way and here is why... if it calculated a route along a given road and you encountered a highway that was under reconstruction with all traffic shifted to what used to be an access road, then the GPS would constantly "recalculate" thinking you had taken an offramp and were now off of the route that it wanted you to be on. This could continue for miles as it keeps recalculating and telling you to take the next on ramp (which may also be closed). Once you reach the end of construction and return to the actual highway, it will recalculate yet again. All of that is completely unnecessary. The assumption is that if you don't know where you are going, you are going to be following the calculated route, even if certain roads no longer match up exactly with what is in the map. The Garmin provides this leeway (which I think is somewhere between 50-100 feet off of the mapped road) to keep from recalculating all the time.

If you know where you are going, then the assumption is that you aren't going to have the Garmin telling you what route to take. In this case, the Garmin will track where you actually are and will be a lot more precise in showing where you are on the map (what exit ramp, etc).

I like it working like this because I don't want constant recalculation when I'm trying to follow a route through an unfamiliar area that may have changed slightly from the last map update, but when I know where I am and am not using a route, I want it to show me exactly where I am...and it does.

Jeff

Jeff(jeff92k7),

Good points. I noticed that too, when driving with my 255w without a route active it will hug the actual road or ramp more. I also read about changing the navigation mode(car, pedestrian, bike, etc) - haven't actually done it. And I here you on the recalculating. Not all roads are perfectly mapped either, and the Garmin(vs. the Maestro3100) is more strict on going off route.

The GPS is a great driving aid. I would recommend to anyone to have one in the car - even ones like my economy versions .

Sometime the feature is useful, like going through tunnel or going under long bridge, or sometime going between high rise buildings. The GPS lock is lost, but it still keeps 'guessing' and when you are at the other end of tunne; it had guessed your position quite acurately all this while.

Yea i can get annoying.

That's pretty cool!