GPS reception errors

[sgoldste01]

I have two TomTom One units (one is a 3rd Edition, and one is an LE from Best Buy). Both units behave as described below, so I don't believe this is caused by an individual unit defect.

When I'm driving in Silver Spring, MD (on Georgia Ave, specifically), the GPS intermittently can't determine where it is accurately. When this problem happens, the error might be off by approximately 50 to 100 yards--enough that it thinks it's off the road, and constantly tries to recalculate a way to get back onto the road. When this happens, I power the unit off then on, and this usually fixes the problem. Sometimes it gets confused again, forcing me to power cycle the unit again.

If I was driving in a metropolitan area with tall buildings, I'd understand this behavior due to signal reflection. But there are no tall buildings in the area where this happens, so I can't understand it.

Has anyone else experienced this behavior, either in Silver Spring, MD or elsewhere? Do you know what causes it?

 

[GAW]

You may be driving on roads that are not mapped correctly on your current maps. Which map versions do you have (tap on lower right corner of the units unit, and then tap on the small icon that comes up showing your application version - it should then give all the information on you unit including the map version).

When I am on new sections of roads, mine acts like this also, and since it is both units - I think it is the maps.

if you have/use Mapshare, you might want to send in the beginning and ending points on Georgia Ave where this occurs.

 

[sgoldste01]

I don't think so

You may be driving on roads that are not mapped correctly on your current maps. Which map versions do you have (tap on lower right corner of the units unit, and then tap on the small icon that comes up showing your application version - it should then give all the information on you unit including the map version).

When I am on new sections of roads, mine acts like this also, and since it is both units - I think it is the maps.

if you have/use Mapshare, you might want to send in the beginning and ending points on Georgia Ave where this occurs.

I don't think this explains it. If you were right, then powering the GPS off and on wouldn't make any difference. The fact that power cycling the GPS fixes it means that something is confusing the unit, and it must be rebooted before it can figure out what's going on.

Also, Georgia Ave. is a big, old, well-established road that has been there, unchanged, for decades. It's not a road that's new or newly modified.

 

[Tim25]

I looked at a map of Georgia Ave going through Silver Spring...Does the problem happen to be in the area just south of the Beltway? The area that looked odd to me is at:

http://maps.google.com/maps?f=q&hl=....041385&spn=0.001574,0.003085&z=19&iwloc=addr

(Assuming maps.google.com is still showing TeleAtlas maps which it seemed to just start doing within the last 24 hours or so...)

At the Beltway, Georgia Ave is shown as 2 lines, one in each direction. At the point I referenced, the 2 lines collapse into one...and the line is placed on the northbound side of Georgia Ave. As you travel southbound, you can be as far as 4 lanes off "the line" and you cut across all sorts of other roads at each intersection....I could see where this could drive Tom crazy. Does it behave any better if you are on the "inside" lane headed southbound? Does it perform correctly as you travel the inside lane headed northbound (right along the line)? If my guess at what is causing this action is right, I'd suggest you report the erratic behavior to TeleAtlas and suggest they maintain the "dual line" approach along this very wide road.

 

[The Spook]

Multipath effects

Hi sgoldste01,

My guess is that you are experiencing multi-path errors. This may be due to ghosted signals being reflected from a nearby building (it need not be tall), or someone in one of those buildings may be operating a re-radiating antennae.

If this were the case, you might receive a stronger repeated signal from them than from the sky. This can cause the symptoms you are experiencing. Are any of the companies along that road involved in aerospace development or research?

To test my hypothesis you could just observe the GPS position coordinates as you pass that area (preferably record them using tripmaster). If the coordinates jump wildly, then the problem is with the received signal, not the map. If the coordinates map as a straight line (plot them using GEarth or similar), then the issue is with the map data. My money is on the former.

 

[VinMan91]

I have read on other forums that it is indeed a poorly made map! I live in Canada and travel through 4 provinces and my TT bounces off course quite often. I have just learned to live with it! Now I do own a One v2, just wondering if I upgrade to a 700 or 900 is this problem still going to be there? I do know that they use a better map than the One!