Hormazd

Does anyone know if the GPS system can be honed to accuracy by the dealer in SW updates. I used to get pinpoint directions when I was in Europe but ever since US delivery and subsequent SW updates, I get the "You have arrived" either 300ft early or I have to drive 300ft past my destination.

beewang

My experince w/ BMW nav system is that it can't be done. BTW, it may not be a GPS issue, rather it was a Navteq mapping data issue.

Keep in mind that the Nav's accuracy is inversely effected by the Homeland Security alert level.

Hormazd

My experince w/ BMW nav system is that it can't be done. BTW, it may not be a GPS issue, rather it was a Navteq mapping data issue.

Keep in mind that the Nav's accuracy is inversely effected by the Homeland Security alert level.
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Thanks Bee, Good point, The US DVD is one variable I forgot to factor in.

robg

Don't know if this applies or not, but I have read elsewhere in connection with handheld units (used for hiking or other outdoor activities) that all civilian GPS is intentionally inaccuate by some % as a "security" measure. Only the military gets 100% accuracy.

browellm

The intentional degradation of civilian GPS was removed on May 1 2000.

beewang

..

drjochen

Yes, 8 months later, (After 9-11) the U.S. reinstitited the "intentional degradetion of civilian GPS" and the range various based on the DHS' alert level (as stated previously, "inverse" relation to accuracy)
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Mine is off, too. I also have a Garmin handheld GPS, which I had with me in the car and it was NOT off. The BMW NAV had me on another (parallel) street, while the Garmin had it right. So it must be the BMW hardware or the map software.

browellm

Ah right. My understanding is also that the US Government can regionalise that degradation, which would explain why it is pretty much "bang on" here.

TBell

Actually, I don't believe that "regionalizing" the deliberate degradation of the GPS signals' accuracies is possible (although localized jamming during war is possible). GPS accuracy will vary with user location on the Earth because the accuracy depends on the number and geometry of the satellites in view, which in turn, depend on user location. To that extent, there is a location dependence, but this dependence changes slowly as the satellites move through their 12-hour orbits. Therefore, a 300-foot error (which, statistically, should be very rare) will slowly evolve over several hours. This degradation was turned off several years ago (as you pointed out in a previous post).

Since the position information that Hormazd got was correct before shipping to the US from Europe, I'd agree that the likely cause is map-related and not GPS-related.

cobradav

The intentional degradation of civilian GPS was removed on May 1 2000.
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Even though there is no intentional degradation now, the military still has encrypted and higher resolution codes not available to the civilian world. Weapons targeting requires far more accuracy than what we get in the commercial world. However, starting with GPS IIR-14 (M), scheduled for launch on 20 May 2005, the civilians will get an additional code/frequency to help resolve ionospheric errors and improve accuracy. The Military gets new codes, anti-jamming and enhanced encryption. Both get an increase in power which should help those in marginal coverage areas. However, just the launch of this satellite will not enable these improvements. It will take many more satellites to enable all these enhancements to be utilized as you need at least three in view at all times at any given receiver. That will take a few years. We'll probably only get three up this year at best.

As far as accuracy now is concerned, it is based on how much processing power the ground receiver has. Some are capable of processing more satellites that others. As you increase the number of satellites in view and are capable of processing their data you can obtain greater accuracy. The GPS Program Office produces a map showing the number of satellites in view over the earth and the expected accuracies that can be achieved. It is something I might be able to download at work.