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2010 2011 BMW 5 Series Forum F10 BMW 5-Series Gran Turismo GT (F07) Forums General 5-Series GT (Gran Turismo) (F07) Forum Nav out by 30-40 yards
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      07-30-2011, 05:45 AM   #1
Noodles23
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Nav out by 30-40 yards

As I approach a junction the Nav display will ay 30-40 yards to go as I miss the turning. If i have spoken instructions enabled I'll be told to turn at the exact point when its too late to do so.

Anybody else seen this problem? Any fix, software update?
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      07-30-2011, 09:47 AM   #2
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um, I think you will find that commercial GPS systems are just not that accurate, especially when there is interference from builidngs, etc
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      07-30-2011, 12:23 PM   #3
Noodles23
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"um, I think you will find that commercial GPS systems are just not that accurate, especially when there is interference from builidngs, etc"

That's probably the response I'll get from BMW service but after 30 years in the space industry I'm happy to go through the workings to show that 10 meters is the usual worst case accuracy of commercial GPS receivers. This also happens in open country rather than urban canyons where not much sky is available.

If that fails it's a simple job to pop a TomTom in the car and ask BMW to justify the difference in co-ordinates (which should be the 1.5m between the recovers rather than 40m).
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      07-30-2011, 03:01 PM   #4
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I have the heads-up display, and while the numerical distance readout is often overstated, the bargraph (not sure this is available without the heads-up display) seems to be more accurate. Also, the voice and the display update rate are not entirely in sync - when the display may read 100M, the voice may say 50M, implying less resolution or update rate on the display. Last, it seems to measure to the center of the intersection, and not the stop lines, which can affect the distance to the turn.
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      07-31-2011, 05:27 AM   #5
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"Last, it seems to measure to the center of the intersection, and not the stop lines, which can affect the distance to the turn."

That's still a long way from being 40yds on English junctions But I don't remember ever having this rather annoying problem with TomToms.
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      08-01-2011, 07:50 AM   #6
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Hmmm ...Have not noticed this much of an error on mine, will have a closer look on the way out of London this evening and let you know.
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      10-08-2011, 08:52 AM   #7
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Yes, you made a good observation as I found my 2011 750li xdrive also measures to the center of the intersection.

This seems to have changed when BMW switched map data vendors.

The older and much more accurate navtech data were based on the "stop lines" as you call them.





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Originally Posted by Noodles23 View Post
"Last, it seems to measure to the center of the intersection, and not the stop lines, which can affect the distance to the turn."

That's still a long way from being 40yds on English junctions But I don't remember ever having this rather annoying problem with TomToms.
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      10-11-2011, 09:33 PM   #8
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I wonder if the maps supplied and the GPS programming have the spheroid and datums matching? Depending on what the maps were drawn to, this can easily make errors anywhere from zero to multiple kilometers, depending on where you are. The US military is trying to standardize theirs to WGS84 (last I heard), but many of the older ones are NAD27 for North America, and I don't know what they use in Germany or the rest of Europe. There are probably over 100 different datums in use, and the map must match the setting of the GPS configuration, or your reported position will not be as accurate as it should be. There isn't any easy way for the user to tell with what we have that I know of.
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      10-12-2011, 08:11 PM   #9
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I'm on vacation in the Upper Penninsula of Michigan, and in one section, the vehicle icon was at least 800' from the road while I was driving. I'm not sure if the map was wrong, or the datum, or spheroid, or a momentary gps anomaly (these are VERY rare)...I wasn't in heavy trees, and it had a good line of sight to multiple satellites. There appears to be some 'lock to road' logic, as eventually, when the location icon got closer to the road, it jumped sideways and then 'latched' to the road. I may call BMW when I get home. I actually had two other gps units with me, I guess I should have stopped and tried them to see what they thought of the situation...might have made for an interesting comparison.
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      12-01-2011, 03:33 AM   #10
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Scotthall BMW in Leeds said they found a fault and recalibrated the GPS, so there was an issue. I'll keep an eye on it.
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