How Far Off


I've been using GPS technology for about 3 years, and in that time, I've noticed a couple of addresses entered into the unit don't always send me to the place where the actual place turns out to be. Most of these glitches can be attributed to the GPS reversing the direction of the street numbers. Up until now, these discrepencies have only been minor inconveniences, but last week, on the Blue Ridge Parkway, near Fancy Gap VA, the address of the B&B we were looking for ended up being 3.7 miles away from the actual inn. I've subsquently re-entered the address, and discovered there are not one, not two, but three listings for the same address on the same road, one being the correct location within .1 mile, one about one mile off, and another (the one we chose, because it was first on the list) almost 4 miles away (all of these locations were on the correct road, just at different points along it).

My questions are: Why does the GPS give multiple locations for an address (Garmin 350) and: Is there anyone who can beat 3.7 miles?



I've seen multiple listings for the same place.

This is part of a response I got from Garmin Cartography when I reported an error in my area.
(The entire response may be too long to post here).

"...In "other" areas outside these driven metropolitan areas, the
detail from NavTeq is usually good, but it is not always quite as good.
You may find that roads are more likely to be missing or are slightly
off from their true position. You may also find that addresses are not
available or the address ranges may be on the opposite side of the
street from what they truly are. These roads have not been field
verified by NavTeq but have been put together in other ways. But
overall the quality of these areas is pretty comparable to the data
from other vendors in this market...overall being the key word.
NavTeq is the premium data vendor in this business by most regard..."

........Garmin StreetPilot c550 / Nüvi 765...........

Accuracy Assistance

To help with accuracy, I normally Google Earth my destination and get the actually long. and lat. co-ordinates before leaving for the trip.

It's more work but it's worth the hassle to limit frustrations when trying to find your destination in a strange neighbourhood.

For example, last Sunday I was traveling to my wife's grand mother's house and decided to use my GPS to determine the accuracy.

Before leaving I entered her address in Google Earth and low and behold the location displayed was up the street from her actual residence. This occurred because her P.O. Box is actually registered and physically located .25 miles away from her house.

To fix this issue, I got the actual long. and lat. information by placing the Google Earth cross hairs at the beginning of her drive way.


Address and locations

On "another site" I read response from Garmin on this same subject. That response explained basically that if a road is two miles long, for example, NavTek knows the range of addresses along that particular two miles, and assumes those addresses are evenly distributed along the stretch of road. If the houses/businesses are actually closer together in some areas than in others, the uneven distribution will screw up the locations. Hard to believe that could add up to a 3.7-mile error - but does explain why my Dad's address is always displayed about 1/4 mile too far north - on Yahoo Maps, Google Earth, Mapquest, Nuvi - you name it. Just out of curiosity, I'd like to see where TomTom's map vendor displays it.

TomTom falls short in US

rajones19 wrote:

...I'd like to see where TomTom's map vendor displays it.

I bet it'll be no better than NAVTEQ (supplier of Garmin). TomTom uses Tele Atlas.

From what I gather, NAVTEQ's map is strong in US and weaker in Europe. Tele Atlas, on the other hand, is the opposite. This is the main reason why I immediately crossed out TomTom from my list when I went on a quest to find my GPS.

Garmin nüvi® 660, iPhone 8gb (Technology is not the solution. It's only a tool to help you achieve it.)