GPS accuracy

[John Costella]

I'm wondering if anyone else has had this experience. We've found that the GPS in our new 740xi in the area around our home (downtown Washington DC) is often inaccurate by tens to hundreds of feet. This not only makes navigation and related functionality (speed limits, etc.) wrong, but also makes activation points for automated windows and the panoramic front camera as well as recorded paths essentially impossible to use. We generally have to drive half a mile to a mile away from our home before the GPS is accurate enough to actually place the vehicle on the road it is on, rather than driving through buildings or diagonally through random nearby parts of the city.

I understand that GPS signals are affected by buildings (in my previous job I did extensive data science on GPS data from vehicles), but not only are DC's buildings all only 12–13 stories high, we've never (and still don't) have any similar GPS inaccuracy with our iPhones (Google Maps, Apple Maps, other Location Services) nor the TomTom Go 620 device that I had until recently.

Given that the car has a much better antenna than our phones or the TomTom, and hopefully just as much processing power, I'm guessing that the GPS software or firmware in the car is just not as well-written and robust as it could be. (Again, I know that these algorithms are not trivial, but they're table stakes for anything relying on GPS.)

I asked for help on this from the Geniuses at our dealership, who referred me to the BMW USA Genius email channel. The latter basically didn't answer the question other than "Please stay tuned to possible future software updates for your BMW, which may include your requested updates and changes." I'm guessing that that might mean that they're fixing bugs in this system (and a couple of other bugs that I reported), but I don't have any experience in knowing whether that means it will be fixed in weeks, months, or years.

[skrontz]

GPS modules are typically OEM components that almost all car manufacturers share, and they all output the raw coordinates into a vendor specific system. Perhaps BMW is using a newer/buggier GPS module or there’s a problem with processing the coordinates within their own code, but I had personally experienced this myself last week when the nav suddenly placed the car way off the current position while driving. It fixed itself in about a minute, but that already caused me to take the wrong exit.