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Discussion Starter · #1 ·
Hi,
I have had my 05 Prius for two months and have been trying to get answers from my dealer and Toyota's customer services (over 4 phone calls and email) what kind of nav system is in my Prius and it's accuracy?
The manual states "occasional error of 300 ft" . I always get an error of at least 300 ft. Once it was about 100 ft,never closer. Tried to find a place at night and never did,"you have arrived at your destination" IT said,no way... I was lost, punched in home and got me back to my road where I live. I asked the Toyota experts and told them my house was half mile from what the nav system showed. They said to take it back to the dealer and have it calibrated. I did and no luck same errors.
I don't know what to do,maybe buy a Garmin and put it in another new car. :(
Anybody else have this problem with there nav system??
Thanks, and this is a very nice and helpful forum.
...Norm
 

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I guess the location must have a lot to do with it. I've had my '05 since September and the Nav system has been exceptional! We do "Meals on Wheels" and the system has proven invaluable to find some of our clients. I have probably used it to find over a hundred addresses and only 2 were "off". Both of these were in new subdivisions that hadn't been mapped. Make sure that your nav is in the proper "area". Don't give up.
 

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If 2 months old, I doubt that it would be covered under the SSC 40J for the updated Navigation maps...

So, how does places like Mapquest or Mapsonline or Yahoo!Maps do for the same address? They pretty much all use the same map database as the Prius. Usually it's not the GPS reception, but faulty maps...

Information on the Prius' navigation system is found in the separate Navigation System Owner's Manual that should've come with your car.
(unit is made by Denso, maps depend on the version of the DVD you have...)
 

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It's also worth noting that the navi system (and, indeed, most navi systems in cars) *intentionally* stops guidance quite a ways before you get to your destination. This is because the designers recognize the possibility of error, not so much in the GPS as in the address data, and therefore want to get you looking for your destination before the system thinks you're actually there.

If you look at the right-hand split panel, it will show the distance the system thinks you are from your destination, even after you have "arrived". It usually starts somewhere around 3-500 feet in my experience, even when the "distance to target" is dead on.

I would tend to attribute most of the error to the map data, actually. GPSs have gotten really good and really cheap over the last several years, and should be able to do <100 feet easily, and <50 feet most of the time.
 

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I compared the Nav system's GPS to a military PLGR unit, and it was accurate within about 85 feet in pure GPS mode. THis was with a clear southern sky view, and after averaging for several minutes. This is about as good as pure civilian GPS gets, claims to the contrary.

Coupled with maps, wheel turn sensor, and the rate gyro, it can do much better than that. The maps (other than the address estimations) are more accurate than the GPS, so the more snapping is done, the better the accuracy. In urban areas that have provided data, the "75 foot" mode shows outlines of buildings that includes accuracy measured in single digits (feet). The more you turn, the better it can map-match, and the more accurately the system can place you on the maps.

Blocked GPS signals, close parallel roads, long stretches without turns all can degrade both location and direction accuracy. And as noted, the address-estimation is not very good, expecially in non-urban areas. However, using GPS to get a fix and enter a memo point, it will rely on the GPS coordinates, not the address estimation, next time it guides you there.
 

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Discussion Starter · #6 ·
Nav system

mrv said:
If 2 months old, I doubt that it would be covered under the SSC 40J for the updated Navigation maps...

So, how does places like Mapquest or Mapsonline or Yahoo!Maps do for the same address? They pretty much all use the same map database as the Prius. Usually it's not the GPS reception, but faulty maps...

Information on the Prius' navigation system is found in the separate Navigation System Owner's Manual that should've come with your car.
(unit is made by Denso, maps depend on the version of the DVD you have...)
It looks like you are correct. I checked the same data on Microsoft Streets 2005 and it showed the exact same distance and error.
Microsoft gets there data from GDC and NAVTEQ.
It seems that DENSO received incorrect data from GDC. Thanks to everyone for your time and information. I am going to let Toyota's customer service know what is wrong,at least, where I live it is incorrect.
Norm
 

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I have the nav update, and my accuracy has improved. I also see more accurate representations of new lakes, streams, roads, and other landmarks.

Yes, in my part of Florida we have new lakes and streams. Many are man-made, and are relatively new. And most of them seem to show up accurately.

Occasionally, the "you have arrived" sounds off too early, but it's rarely more then a block or two off in this part of the country.

One other thing: When they did my NAV update, the service guy neglected to reset my "location." I checked it and corrected it.
 

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Navigation errors with GPS using POI icons

Has anybody else experienced wacky errors using the POI icons? In (desperate) search of coffee the other day, my husband and I located the nearest coffee POI, followed the directions to the location, which turned out to be a private home in a subdivision--and I mean clearly a private home--identical to neighboring houses, toys in the yard, etc. Should I have knocked on the door and inquired about the coffee or called the number the GPS provided?
 

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IMHO, the worst direction problem is when it calculates that you need a left turn at an intersection when in reality that address is to the right. More an algorithmic error than a GPS one. When the NAV is wrong, the reason varies.

Worst data problem: storing street names as (for example) xxxxx ST in some cases, and STREET in others.

Not always worth relying on, but usually worth consulting...
 

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I've bee using GPS systems for years. I usually find accuracy problems arise in two situations:

1) Not enough satellites connected (3 connections work, but not well).
2) Maps.

The worst case of (2) I found was on vacation in NM. The map seemed to be off by 100-200 feet. I kept passing turns before the GPS flagged them. It was a real nusiance.

Interestingly, my portable GPS was accurate enough to flag a speedometer error of almost 5 MPH on one of my cars. It was confirmed by one of those radar warning stations along one of the road.

Gary
 

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When looking for coffee, did the POI's address match the house, or were you relying on Lat/long. position?

What some have theorized is that the map system has address ranges within certain points which could be miles apart, then if you are midpoint between the ranges, then the address should be exactly between the ranges, but in reality this is not the case. Map Info, an old map program I had access to in early 90's did this, but address ranges were between intersections.
 

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I have ver 3.2 which is GDT data. Address enpoints at intersections has not been my experience. If it were true, it would not have me turn left when I should turn righ because of the address desired.

It did suprise me about one thing. At my friend's condo building, NAV lady says her building is no the left, but actually it is on the right. That is really unusual for the NAV system, it usually gets odds and evens right.
 

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None of the Maps online or on GPS can find my house correctly. This is probably because my street is in the shape of a J with me at the end of the hook. Instead of 17, I have to put 97 in for the house number (which doesn't even exist). If I use 17, it puts me near the beginning of the street (a couple of 100 yards off).

This error is common to every mapping program I've tried (mapquest, yahoo, MS Streets & Trips, Mapopolis, Garmin, etc.).
 

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The GPS itself is VERY accurate. Only when it loses contact is the error noticible and then the system just does a linear extrapolation while it is reacquiring.

The map database is variable, but typically excellent. In urban LA it even knows about the left freeway exits, which is a big help if you aren't familiar with the area. It also performed amazingly well in Napa. Yesterday in Santa Ynez we found a few wineries where the tasting room just wasn't at all where the system thought the "winery" was. We also tried to find the "Hitching Post" restaurant (can you tell we watched "Sideways" too recently) and it turned out that the database had only the street and not the street number for it, so it stuck it at the intersection of that street and
the nearest major highway in the town. Be nice if it had a warning for that! We figured it out by closely studying the "info".

OTOH, it got us very close to a very obscure address out in the middle of nowhere in Paicines, CA. The town of Paicines consists of a country store with attached bar and dance hall. It wasn't perfect, the nav system announced the destination maybe a quarter mile before the driveway, but I actually thought it was pretty impressive. I suspect it does some form of interpolation or extrapolation to get street addresses in remote areas.

The one thing it did do that was mysterious was to insist on routing us to the I5 after we were pretty sure we'd chosen a route up the 101 from the 3 route choices. We did confuse it by missing some turnings and choosing a route back other than what it was suggesting, causing it to recalculate the route several times. We eventually forced it off that course by setting a preferred road, but we were never sure if we did something we didn't mean to, or if it somehow reverted to "Quick1" during the recalculation process. By the time we did that, the time estimates for the route it was trying to force us on was almost twice the time estimate for the corrected route once we input the preferred road (5 hours vs 7.5). Maybe we just annoyed the "Nav Lady" by ignoring her, and she wanted some revenge?
 

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incorrect map data

Both Navteq and Tele Atlas (who bought GDT) have places on their web sites to correct map data. However, correcting the data means it will (maybe) get into some future revision of the nav database.

My Prius shows the street I live on continuing on to the north from my house, while, in fact, I am the northern most house on this section of my street. The road does start again, after several fields and woods.

I complained to Navteq and they politely informed me that their data was correct and gave me a URL to a map of my house showing the street as interrupted. I checked on the Tele Atlas site before complaining to them and their map is correct too, almost; they show the road continuing several feet beyond my house before stopping.

So both companies have correct mapping data for my house, but it isn't on my DVD. By the way, Tele Atlas charges $90,000 per year for the US map database. I guess we're driving real bargains...

The POI data comes from infoUSA for those of us in the USA, and their site provides no way of updating their information that I could find. They misspelled the name of one of my favorite restaurants, so I couldn't find it with the nav. Luckily, I remembered the way....
 

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Just went on Navteq's website, they don't list Toyota as a vehicle manufacturer that they support, and you have to select one to give them an update.

How do you check if they have the current data if you can't see their maps?
 
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