Last post on Dec 06, 2013 at 1:02 PM
You are in the Toyota Avalon
What is this discussion about?
Toyota Avalon, Sedan
#10033 of 14965 Re: Stonewalled re Navi system [n0v8or]
Nov 10, 2005 (12:44 pm)
You're correct is saying that mapping programs use some sort of formula to estimate the location of a street address. Not only do NAV systems work that way, so do programs like Microsoft's Streets & Trips. The best they can do is get you close to the actual address.
That being said, you shouldn't be shown to be on a street other than the one you are really on. When I got my 2004 Solara with NAV, it said that the street I live on was called by the name of a street nearby. Toyota issued a recall for the NAV system which fixed that problem and probably a lot of others I never knew about. I suspect if enough people are dissatisfied with the accuracy of their Avalon NAV and complain directly to Toyota, a recall might be in the future.
#10034 of 14965 Re: engine knock [3puttmax]
Nov 10, 2005 (12:49 pm)
I forgot to mention that these are not "lifters" in the conventional sense. They are not located directly in the serial path between the camshaft lobes and the valves. A fulcrum is interposed between the camshaft and cam follower. The pivot point (ground symbol in a statics drawing) of the fulcrum is semi-compliant to take up the lash. The fulcrum pivot rests on top of the hydraulic adjuster plunger, while the cylinder (body)is fixed in cylindrical cavity in the head. Only the plunger moves.
Much easier to draw than to describe.
#10035 of 14965 Some Words Regarding GPS
Nov 10, 2005 (1:12 pm)
I've noticed a lot of discussion regarding GPS accuracy, and I just thought I'd chip in my two cents.
Fact 1: The common GPS systems that are commercially available are accurate within 65' of true position. Various techniques and error-corrections can reduce this to 4" (but obviously, this is not available on most passenger vehicles).
Fact 2: The system used by Toyota (Denso) automatically places the car on the nearest street going in the same direction. This means that if GPS places the car 5' to the right of a freeway, but there is no road there, the system would show the car as going on the freeway. This is done only up to an unknown (but probably small) range (i.e. if you're driving in the middle of nowhere and the DVD doesn't contain any road information there, you're not gonna be placed on some random road 200 miles away going in parallel). This error-correction algorithm is very much necessary since, due to the relatively large margin of error on the common GPS system, the system would almost always see the car as being off any real road. Only by guessing which road the car is nearest can the system provide direction on where to turn next.
Now, with these two facts in mind, let's talk about the accuracy of the system.
Most of the complains are regarding the placement of the vehicle on a parallel street. Now, I believe what is happening underneath is that the GPS signal is off (perhaps right in the middle of two adjacent streets), and the system's error correction algorithm (see Fact 2) automatically places the car on a street that goes in the same direction. This should be okay in a sparsely populated suburb, but in a dense city, the (up to) 65' of error and the error correction may result in placement of the vehicle on an adjacent parallel street. This is not exactly Toyota's fault, since the mapping system was given inaccurate information to begin with, and I'm sure most of us know that working with inaccurate information can be difficult, or down right impossible.
The other class of frustration seems to originate from the system reporting the arrival at a destination when in fact the car is still tens of yards away. What I've observed is that the system actually reports you have arrived a little distance before the car arrow icon and the red target destination icon overlap. I'm guessing that this is by design so that the driver would be signaled just before actually arriving at the destination to allow time for reaction (e.g. turning into a plaza).
So in the end, most of the frustrations experienced by Avalon GPS owners are caused by the combination of GPS error margin and the error-correction algorithm. Realistically, there isn't much any of us can do (not even Toyota) until more precise GPS systems are widely available.
Just my two cents
#10036 of 14965 Re: engine knock [n0v8or]
Nov 10, 2005 (1:50 pm)
"Much easier to draw than to describe."
Perchance is there a drawing among all those pages that you downloaded, that you might be able to pass along here?
#10037 of 14965 Re: engine knock [gws]
Nov 10, 2005 (2:07 pm)
Posting it here would run afoul of Toyota's copyright. I don't want to get the Edmund's folks in trouble, particularly as thay have been so kind as to host this forum at no charge to readers. See message #9420 or #8655 for instructions how to send me a private communication.
#10038 of 14965 Re: Stonewalled re Navi system [lbs1]
Nov 10, 2005 (2:15 pm)
Actually that's very possible (talking about the difference in accuracy between low and high street addresses) because the geocoding process (way of mapping addresses to lat/long) works with blocks of addresses of a time. That is, every address is not individually mapped to a lat/long location. Only start/end points (or specific intervals) are mapped and everything in between is calculated. So it sounds like the map data in your area is not as accurate as it could be.
As the other poster said, you may need to set your destination by adjusting the location via the map if you need to be more exact.
As for being shown on a different street that is 100-150 yards away, how far is the correct street from your physical location?
For more info about geocoding, see
#10039 of 14965 Re: Adding iPod [05avforum]
Nov 10, 2005 (2:35 pm)
Thanks much. I'll try this evening and let you know.
#10040 of 14965 Re: Toyota Dealer [fragmire]
Nov 10, 2005 (2:59 pm)
Not off-topic at all, I hope someone can suggest a place for you.
#10042 of 14965 Re: Some Words Regarding GPS [fragmire]
Nov 10, 2005 (3:29 pm)
Your description of the "parallel streets" GPS anomaly is probably incorrect.
I was quite puzzled about what was causing this since it is often the GPS system "itself" that put me on, guided me too, the street I am currently on when it decides I'm on a parallel street.
But then I happened to be driving in one of our mountainous areas and the system kept repeating, again and again, the same directions.
I now think that what is actually happening is that the system is momentarily losing contact with one of the three GPS satellites it requires for operation. Once it regains contact it completely resets its past memory and recomputes your location. Since it now has no past history you may end up anywhere within the system's accuracy tolerance.