[Rickanns]

Here is a question for someone who is a lot smarter than me and several other folks.

I have a 2007 Touareg with Nav and also a new Lexus ES350 with Nav. When I first tested the Lexus Nav driving home, the system ended before I made the last turn to my house. When parked side by side in my driveway, the long/lat readings on the two systems are different. When I checked the readings with my Magellan handheld gps, it agreed perfectly with the Touareg Nav, indicating to me that the Lexus Nav was off. The long/lat readings were as follows:

Lexus N33 30 21 W101 53 42
VW N33 30 36 W101 53 71
Mag. N33 30 363 W101 53 711

As you can see, the Lexus is several seconds off both North and West from the other two. Also, on a trip to our daughters house in Dallas, the Lexus Nav again ended well before the last turn and was at least a block off.

The Lexus has a display which shows the address of your current location. This display shows the address of 9773 when in my driveway, but the actual address is 9709. The last address on our street is 9713, so the 9773 address is totally fictitious.

On a test trip to my pharmacy, the Lexus Nav told me that the store was on the south side of a major artery when in fact, the store is on the north side of the street. Again, the system is off a couple of hundred feet at least.

Here's a kicker. When I took the Lexus in for the 1k checkup, I was given a new RX with Nav as a loaner(that's a whole "nother" story). In my driveway, the RX showed exactly the same readings and address as my Lexus ES. So, if there is an inherent problem, it is not with my particular car. I asked the dealer to check my Nav for this problem, and their answer was,, of course, that everything was working correctly and it might well be.

Both the Lexus and the Touareg systems are Navtech's.

Several of us on two Lexus forums are discussing this, but no one has a clue as to the answer.

Can anyone over here offer any insight???:confused2::confused2::confused2:

Rick

 

[spockcat]

Impossible that a VW is better/more accurate than a Lexus. Oh the irony. :lol:

 

[Rickanns]

Needless to say, one of my first thoughts, too.

Totally worthless if you are geocaching around town.

Rick

 

[Vegas Matt]

Impossible that a VW is better/more accurate than a Lexus. Oh the irony. :lol:

Nice

I wonder if there is some GPS calibration that needs to be done on the Lexus? I recall some compasses that require you to turn in a circle to calibrate it, maybe there is something similar to calibrate the Nav system?

I'm certainly far from an expert on this stuff, but it's an idea. My Garmin handheld GPS simply autolocates itself when you turn it on, and it (probably much like your Magellan) seems very accurate. To me, this doesn't sound like a Navteq problem, but the GPS software/hardware being inaccurate in the Lexus system.

I'll write back if I think of anything else. Good luck Rick!
Matt

 

[Rickanns]

This guy on CLubLexus offers some interesting insight. I am still mulling things over is my slow, old mind.

My two cents worth regarding mapping location/address number issues:

Re: address number accuracy--try this...plug in an address for a specific location you know does not exist but is within the range of valid block numbers--e.g., tell the nav to give you directions to 101 Main St. if you know for a fact that 101 Main St. does not exist at all, but is within the valid range of 100-200; if it is able to calculate a route to that "exact" location, then that shows that it is extrapolating the street number based on the block range for that street (and perhaps on any existing locations it may have stored in its database), rather than because there is an exact match for that address in its database. For the nav to accurately display the exact location of any given address, it would have to reference a database that cross-references the latitude/longitude for every single valid street address/number--by all means not impossible, but would be painstaking to create/maintain since any specific street address would need to be visually/physically confirmed as to its actual location.

Re: location accuracy of car nav vs. handheld--it is important to note that many/most in-car nav systems rely on a combination of GPS and wheel sensors/gyros in order to best accurately display your vehicle's current location on the map screen, while almost all handheld/portable GPS units rely solely on GPS to display (as accurately as possible) location. While the streets shown on the map are assumed to be depicted as accurately as possible, relative to other streets/landmarks...one has to keep in mind that GPS-based positioning is not done by determining what street you're on, but rather, what latitude/longitude you're at. I mention this because some portable GPS units (like my Garmin iQue 3600) allow you to display your current location either based on the nearest street you're on (if you're on a road, that is) or according to your current GPS-calculated position; this option clearly implies the possibility that the street map data currently in use may not always correspond to GPS-based coordinates--e.g., you can visually confirm out your car window that you're exactly at the intersection of two streets but GPS shows your location on the map display as being a dozen feet short of it--but at a GPS-calculated latitude/longitude coordinate that is assumed to be fairly accurate. IOW--if a GPS-based nav unit is indicating that you're at latitude X/longitude Y, while showing on the map that you're at the intersection of two cross-streets...which of the two data points would be considered more accurate?

Also, I believe quite a few portable GPS units allow you to select/enable WAAS (Wide Area Augmentation System) in order to increase GPS accuracy to as little as 3 meters; dunno if car navs implement WAAS...it might be a bit overkill for vehicles that use speed sensors to aid in plotting vehicle location on the map display.

Now that I've bored you all w/ this long post, I will concede in that it's one thing if the vehicle nav is showing your location to be off by say 100 feet or more--that's one thing...but IMHO nav accuracy isn't that big a deal if we're talking only about a dozen feet or so.
__________________
Tony


Rick

 

[Vegas Matt]

It sounds to me like there is some misinterpretation of the map location in regards to the GPS longitude/latitude data, in addition to the misread of the longitude/latitude by the Lexus. I think pretty much all handhelds (and possibly the VW) are WAAS-enabled, yielding the long/lat numbers that are more accurate to each other. Maybe the Lex doesn't have WAAS, or there is just something else at play.

In regards to this:

if a GPS-based nav unit is indicating that you're at latitude X/longitude Y, while showing on the map that you're at the intersection of two cross-streets...which of the two data points would be considered more accurate?

I think that in a vehicle, generally the map should be the most accurate item over the long/lat, since when we are driving, we're generally more concerned with streets and addresses, not long/lat locations. Some instances (ie geocaching) need the long/lat accuracy, but (and I may be wrong) most Lexus consumers are probably more interested in finding the nearest stores or coffee houses, not the can behind the rock on the mountaintop.

As far as using the vehicle sensors to aid in navigation, I could see this being done in "dead-reckoning" situations where the GPS signal may be obscured, like in a tunnel. In my opinion, using this input otherwise might just confuse the system.

But, I personally still think that long/lat should be the basis for location, then the map applied to that data. If the foundation (long/lat data) is bad, anything you build on top of it (map data) is possibly inaccurate. It seems to me that this foundation data is inaccurate in the Lexus, yielding inaccurate navigation info.

My way of fixing it: Trade it in on a VW

Matt

 

[briscowings]

Heck you live in Lubbock can't you get anywhere by just jumping on the loop or Slide?

Thanks
Ken

 

[Rickanns]

Heck you live in Lubbock can't you get anywhere by just jumping on the loop or Slide?

Thanks
Ken

:razz::razz::razz::mrgreen::mrgreen::mrgreen:

82nd St is now developed all the way to Wolfforth.....Milwaukee is developed from 98th to 4th. Besides, at our age, we might forget where we live!!!!

Actually, the !%%$%$&#&^ thing ought to work right and I don't think Lexus is grasping the problem.

Rick

 

[MarkTTU]

I know I'm bring to life an old thread, but Rickanns I thought it might interest you to know that the map data for Lubbock is off in a couple of GPS databases so its possible that the Lexus map data is from a different core database...

Essentially there are a couple of GPS map databases out there that have all the streets in Lubb shifted a few feet. I found this little tid-bit out from a buddy who works for the city; apparently it causes no end of trouble for them in keeping their database up to date with where every cable, wire, and pipe are under the streets.

 

[nltomba]

Get an 04 nav system. According to it my town of 150000 people is still largely undeveloped with hardly any roads:shock: