GPS recalculating

Would be nice to know why NUVIs recalculate.

Perhaps the road was new and the NUVI had an older stretch of road on which it was navigating.

Simulation might be a way to find out what the map had. If you could identify a spot not too far from where the problem occurred and then start at that location using the "simulation" feature ("go"ing on to your destination), you might see that I75N was not really straight at that point, but might have had a detour around an under-construction improvement to I75.

If you try this, please report back to us.

Does your unit have a traffic reciever? When I was driving on a long stretch of HWY 401 this past summer my 265WT kept routing me off the HWY. The route on the HWY was perfectly clear, yet my GPS kept telling me to route through small towns. I suspect this had something to do with some traffic alert that was in the recent past, and it was getting me to avoid it. (Strange)

I'm not sure if this is the case here but there have been times when the GPSr snapped me to a parallel road to the one I was on and tried to reroute me back to the thoroughfare I was already traveling on. Sometimes the signal improves enough that in the course of recalculating and recalculating that it figures out that I am on the roadway it originally expected. This happens every now and then on the New Jersey Turnpike (I-95) and in the valleys of Manhattan.

My 265WT does this every time I go home. I turn left onto a road that has a driveway for a cemetery next to it and the 256WT will show me in the cemetery every time. The cemetery drive curves away after about 1/4 of a mile and I will magically jump onto the road. This happens even if I am at twelve to fifteen feet accuracy and these roads are more than twenty feet apart except right when I turn onto the road. It doesn't seem to matter if I drive on the left side of the road so they are a good forty feet between me and the cemetery drive. It will always show me on the drive until it curves away. I have a similar problem in town when I drive on some alleyways that my Garmin doesn’t know exist. It will jump me from the street on the left to the one on the right and back again.

It's possible that the map is off a bit to the actual road and the GPS feels that you have gone slightly astray.

The other possibility is a gap in the map.

I had a case where the a particular ramp was shown on the GPS map, but the GPS did not recognize the ramp until I got about 1/3 of the way around. I contacted Garmin and advised them of the problem and it was corrected in the next map update.

In your case, the gap might only be a few feet long, but it's enough for the GPS to think you went off route. I would get the coordinates as accurately as possible and report this to Garmin.

Does this highway have a toll? If so, the problem you describe can be caused if you have the avoidance set on for toll roads.

I still belive this had something to do with the traffic reciever. (strange)

No the road was I75 north from Dayton,Ohio, it was a long straight stretch and nothing going on except the two times it recalculated to the same road , mileage and arrival times changed very fast ten started where it left off as if it had never happened,and no it does not have traffic capabilities.Thanks for all of your insight.

I have had my GPS recaculate and try to route me through a small town more than once. The new highway/bypass I was on did not even show up on the GPS. The GPS thought I was in the middle of a field. Once I passed the small town and merged back onto the old highway the attempts to recalculate stopped.

Don't think I've ever seen mine say "Recalculating" without me taking a different turn or doing something like that.

My NUVI 350 will tell me there is a better route and then put me on the same route I was going on.
This is in a place where there is no other route near by, not even a small farm road.

if you keep maps up to date then probably that's why. i am driving now with 1yr old maps on my Garmin NUVI 265T and I often see Recalculating, especially on ramps, new redesigned intersections and so on.

oh ... BTW, in June/July we did a road trip to Pittsburgh, PA geeez, this city is one huge construction yard
my GPS got lost completely close to downtown (across the river that was) to the point it told me to drive into the Bridge leading to Downtown and then couldn't even properly position my car on correct street (like map or GPS signal was off). In the end it couldn't find a way out of there

need to get lifetime map updates finally I guess hehe

There have been creeping 'map registration errors' in my area . . or else the GPS constellation has shifted.

Major highways which haven't moved are now several 10s of meters offset to the point where the damned navigators (plural) put me on the wrong road and try to reroute me to the 'correct' one if I'm navigating - it just shows me offset (though locked to road) if I'm not.

Where this REALLY blows is that if it doesn't think I'm on the highway (most often it manifests itself by me being reported as on the collector road next to the highway) it won't report traffic issues and I've been stung by that a number of times, because they aren't on the road that the nav thinks I'm travelling on.

With the release of the 2009 mapping sets my house changed sides of the road (actually, it now has my street (which hasn't changed in 20 years) apparently in my across-the-street neighbor's back yard - so I had to manually create my Home waypoint so that it doesn't take me to the next street over.

Garmin is losing it.

You might be losing satellite signals cause my Garmin does the same thing. Sometimes it thinks its driving on the frontage road and I check the GPS signals and the accuracy is between 80-100 feet when its usually 15-20.

I am sorry to say that I agree, Garmin is going backwards. Thought I was doing the right thing upgrading the firmware, then buying lifetime maps and loading the newest map, but I truly feel my Garmin worked better BEFORE all the updates. It is really disappointing, to find the rural roads in the county next to me now have the road names less accurate after the update I paid $80 +/- to get.

We are in a period of increased sunspot activity now and for the next several years. There has been a solar storm going on since early August. All this interferes with satellite reception and it will be more difficult to maintain an accurate position at all times as you drive.

http://www.almanac.com/sunspotupdate

This could account for the poor performance described in this thread.

See also a similar thread on this site:

http://www.poi-factory.com/node/30254

dobs108

I had thought that it was just new stretches of road/inaccurate mapping but sunspot activity could certainly be partly responsible too.

Just went through Ooltewah on way to Chattanooga and was getting back on I75. This area has had massive highway work done over the last three years and what I encountered was one of the last things done.

I was traveling perpendicular to I75. It used to be that one got on I75 South by going under the freeway and making a left turn onto an on ramp. The last work done was to have you stay right and then get on the circular ramp that led up to the freeway.

765T if course was "lost" and recalculating several times until I reached the point where the old ramp merged with I75. At that point "jill" was happy again.

Probably the road had been altered.

The solar cycle that is upcoming is predicted to be a very active and strong one. Yes it will affect communications and satellites....etc. You can keep an eye on it's activity at these websites.

http://www.solarcycle24.com/

http://solarscience.msfc.nasa.gov/predict.shtml