OK, so what does this "recalibration" feature on the Nav Sys do exactly?

e9999

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the other day, I was skimming the owner's manual for the NavSys when I came across a brief mention of there being a recalibration feature built in that you can use when you change tires. Anybody knows exactly what that does? I would imagine it could introduce a GPS-derived correction factor for mileage on the NavSys side of things, although, that does not seem obvious to do. Conversely, I would doubt it would affect the odo and speedometer on the dash, those probably are kept separate.
So anybody with bigger tires has ever tried to see what that does and figure it out?
 
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It's suppose to calibrate the vehicle position on the screen. Recently I noticed my position was off and did the calibration along with the position calibration. Now it is very accurate when approaching intersections and such. Although, I don't know if it was the tire calibration or the position calibration because I did them both at the same time.

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Well, maybe not entirely. CrusrDug is absolutely correct. All GPS devices has to be calibrated/reset once in a while in order to "find" its accurate location. I'd assume the LX/LC NAV is no different.

Same goes if you turn off a GPS in LA, jump on a flight and turn it back on in London. It might not be accurate at all on the get go.

And a follow up question;
Anyone knows what data (how much) the NAV system is loaded with. On a U.S. spec LC/LX, does the NAV system contain the data for Europe/Middle East (on most portable units, the data is there, but you have to purchase an unlock code in order to get to it).

Actually two;
Anyone knows if the U.S. data can be upgraded? For anyone who bought i.e. a 2000 LX with NAV, there's been a lot of changes since (new streets/roads/subdivisions).

(sort of reasons I prefer the "stand-alone units; easier to upgrade and can be used in several vehicles).
 
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The calibration is pretty similar to what I've done with electronic compassas.

I'd guess that there's an electronic compass that is used in colaboration with the GPS as a way to increase accuracy, and that it's the electronic compass that is being calibrated.
 

e9999

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the manual says specifically that it is for "new" tires.
so must have something to do with distance.

anybody?
 

uHu

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That means the Nav is doing some Dead Reckoning to improve the accuracy, which would come into play particularly when aproaching intersections, and also otherwise between satellite fixes.
Tunnels & when high buildings etc are (partially) blocking signals.
This is a feature that aftermarket units normally don't have. I.e. connection to the speedo.
 

e9999

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That means the Nav is doing some Dead Reckoning to improve the accuracy, which would come into play particularly when aproaching intersections, and also otherwise between satellite fixes.
Tunnels & when high buildings etc are (partially) blocking signals.
This is a feature that aftermarket units normally don't have. I.e. connection to the speedo.


yes, that could be it or part of it, but the effect of a "new" tire (I don't think they mean upsized tires) would be so small for your average dead reckoning very short issue that it seems odd they would have to worry about that.

anybody has big tires and wants to do an experiment (before and after "recalibration" as far as range, speed etc on the NavSys and (but likely not) odo?
 
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GPS never has to calibrated at the device level. The calibration is done at the GPS satellite.

For the LX Nav system, the calibration function is done for the dead reckening system, which ties into the wheel speed sensor and reverse sensor.

The map data can alway be upgraded. Inquire from your local Lexus dealer for the new updated map on DVD. Get ready for sticker shock :eek:

The map data on the US LX/LC will not contain anything outside of US/NA.
 
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I was under the impression the auto calibration for new tires was assuming the tires are a certain size, and that they'll decrease in diameter over miles. As 97FZJ80 says, I think this is only useful when the GPS loses satellites and has to estimate your position. Sometimes I'll be driving in a rural area and the nav will show me driving off the road. When it receives an update, it gives a voice command ("proceed on highway xxxx"). Otherwise, GPS signals come in at 1 Hz, so you should always know your position correctly (within a few meters) regardless of tire size as long as you're receiving 4 or more satellites.
 

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