[APGoldman]

First of all, I have found this sight very useful. My T-reg (as others owners have called their Touaregs) is going in for its 5k and I have noticed several problems that other owners have found i.e. the time is 7-10 min fast a week, and the air bag fault light if on. I am using this to prepare for a fight if my dealer if he will not fix the problems.

Anyway back to my current problem... I am noticing that the NAV is always a few feet behind my current position, even when I'm zoomed in all the way. What I mean is, once I pass a road the NAV has not passed that same road (like it is 30 feet behind me....) I know that GPS is accurate to 5-10 foot, but 30 feet there has to be a problem..

The funny thing is that when the NAV is giving me directions it is right on the money.

I have seen and used NAV's in other cars BMW, MB, Lexus and they all seem to be fine

Anyone else notice this, I want to mention it at my 5k... is it just a software thing??

Thanks you

 

[Tahoe]

GPS at its best, with WAAS (Wide Area Augmentation System) provides a position accuracy of better than three meters 95 percent of the time.

I am not sure if VW's nav uses the new WAAS, given that WAAS satellite coverage is only available in North America.

With that said, with out WAAS it is not uncommon to have a GPS error on average of 45 ft.

You may still have a problem with your GPS system but I just wanted people to know that GPS is still not perfect. Another source of your problem could be the Navtech's maps, which I have found to be quite inaccurate at times, or a receiver clock error. Good luck getting it worked out.

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Sources of GPS signal errors


Factors that can degrade the GPS signal and thus affect accuracy include the following:


Ionosphere and troposphere delays — The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error.

Signal multipath — This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.

Receiver clock errors — A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors.

Orbital errors — Also known as ephemeris errors, these are inaccuracies of the satellite's reported location.

Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.

Satellite geometry/shading — This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping.

Intentional degradation of the satellite signal — Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers.

 

[spockcat]

Either the speed of nav system isn't high enough to keep up with your rate of travel or your nav system needs to be recalibrated. Check this my 1:38 PM 8-11-2004 post in this link: http://forums.vwvortex.com/zerothread?id=1519732&postid=15308462#15308462

 

[APGoldman]

Hey Spock can you help me out with that calibration thing you refer to..

I am in the map tap zoomed in all the way (0.05)... Which one is the setup soft key... the last one on the bottom right?? in that menu I only have three choices for my POM and i not see any softkeys on the right....

What am I doing wrong