: Accuracy of factory Installed GPS



Taylor R
10-23-07, 10:36 PM
I've had a heck of a time with my Factory Installed GPS not taking me to the addresses I've programmed into the unit. First I wanted to see if others have had this same problem, and Second if you have, I wanted to know what experience you've had with GM to try to correct the problem.

Thanks for your input

dkozloski
10-23-07, 10:57 PM
Rather than have every street address in America stored in the unit. It calculates where a particular number would be on an average block. In the case of my address, the city blocks in my area are very small so it's off by fifty numbers. The map data and GPS system is inherently very accurate as witnessed by the little arrow going right down the center of the road even on the most sensitive setting. If my theory is correct there should be some areas of the country where the numbering scheme is a lot closer than others.

Heavy_Metal
10-24-07, 10:45 AM
The map data and GPS system is inherently very accurate as witnessed by the little arrow going right down the center of the road even on the most sensitive setting.

I think the system uses the map itself to help locate the vehicle when it comes to the last 20 few feet. When I drive off of the road and then come back onto a marked road, the arrow will follow along side of the road for a few seconds and then it snaps to the road (exactly on the road). Also when there are two parallel roads 20 feet apart it has a hard time telling which road to select. In that case it seems to go by the path you have taken to the road rather than the GPS signal.

I use the navigation a lot and find it really helpful. I agree that it does not always tell you the exact location of the driveway, but it is almost always very close. For street turns it is usually within 20 feel, and for address locations you just need to start looking for the numbers when you get close.

dhemrick
10-24-07, 05:03 PM
Rather than have every street address in America stored in the unit. It calculates where a particular number would be on an average block. In the case of my address, the city blocks in my area are very small so it's off by fifty numbers. The map data and GPS system is inherently very accurate as witnessed by the little arrow going right down the center of the road even on the most sensitive setting. If my theory is correct there should be some areas of the country where the numbering scheme is a lot closer than others.

Same experience here. In my town, most neighborhoods are very new and are numbered (presumably) based on some sort of standard to which the GPS appears to also adhere to. I have very good luck with almost all addresses.

However, my neighborhood was built 23 years ago by an independent developer. It was out in the country at the time, so he just numbered the houses sequentially starting at 101 with odd numbers on the left and even on the right. I'm the fourth house on the left, I got number 107. However, the lots are much larger than your standard suburban lot, so the GPS tries to tell me that 107 is much closer to the beginning of my street based on it's algorithm.

Interestingly, when I use google maps to locate my address, it puts me at exactly the same wrong point two houses away as my car GPS, so they must be using the same algorighms.

Conversely, when I set my home location while parked in my own driveway, it actually thinks that it is at address 137 which doesn't even exist on this street.

Skibanker
10-24-07, 10:38 PM
Taylor, I'm guessing that when you say the unit won't "take" an address input, what is really happening is that the unit wants to see abbreviations differently from your input. Sometimes, it wants "N" Main St instead of "North" Main St, for example. Other times its the other way around. Sometimes, its 1st Street and other times, its First Street. There's just no way to tell in advance what it wants to see. So, my only advice is to vary the abbreviations until it sees what it wants.

Heavy_Metal
10-25-07, 07:05 PM
Taylor, I'm guessing that when you say the unit won't "take" an address input, what is really happening is that the unit wants to see abbreviations differently from your input. Sometimes, it wants "N" Main St instead of "North" Main St, for example. Other times its the other way around. Sometimes, its 1st Street and other times, its First Street. There's just no way to tell in advance what it wants to see. So, my only advice is to vary the abbreviations until it sees what it wants.

I agree, there is a lot of inconsistency in the way abbreviation are stored. It often helps to enter the city name first so you only need to try the first few letters of each way they may have spelled the street and then push the list button. People that can't spell learn these tricks faster, haha. This also helps when it can't find the house number for some reason.

gunner13
11-24-07, 06:20 PM
Same experience here. In my town, most neighborhoods are very new and are numbered (presumably) based on some sort of standard to which the GPS appears to also adhere to. I have very good luck with almost all addresses.

There is a "standard" and the USPS is making a real effort to impose it on us- the national manager of the program is both a neighbor of ours and a member of a couple of the same Corvette clubs to which I belong. Even those bureaucrats are aware it's a very long term process - there's a LOT of understandable resistance to changing an address whether it's residential or business. The "grid" they want to use will, when finally established, work to the benefit of not only the USPS but also for public safety and private package delivery services. As you noted new construction fits the program without a problem, it's the existing structure owners/tenents that will slow things down.

-= Gunner =-
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-= www.tail-gunner.net =-
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