[Chris Brynner]

If you take it off CarPlay and look at Maps, it should show the cellular circle if it's not using GPS. But, if you take it off CarPlay, it corrects, doesn't it? I think something's weird about the reception in the car and its communication to the phone.

Correct, if I take it out of CarPlay it corrects. I agree that it’s definitely something wrong with the comms between the i4 and the phone. Hard to know if it’s a bug in iOS or the car though.

 

[Chris Brynner]

This happened to me again last night. Turning off CarPlay and back on from the i4 devices screen didn't work. Instead, what happened was:

1. Turn CarPlay back on, wait a bit for it to connect
2. Once music starts playing again, switch to the CarPlay screen and open Maps
3. See that the position is correct on GPS
4. Watch the position suddenly migrate to nearly 1km south from my location

Interestingly, the location it moved to was the approximate location of a cell tower. The last time this happened, the offset (at the end of my commute) was 1km north, and there's also a cell tower just about 1km north of my driveway. Theory: the initial positioning data being provided by wireless CarPlay is garbage and it's falling back to the location of the cell tower it's connected to.

 

[Chris Brynner]

That sounds like interference to me.

Please note: it must be something in the GPS signal reception. There’s literally nothing else it could be.

I disagree... it might be signal interference, but there are a number of other options.

For one, I believe wireless CarPlay receives its GPS data from the car (i.e., not with a GPS signal booster but with data over the wireless connection). Since the BMW app displays the correct position, unless there's a second GPS antenna, it doesn't seem like strict antenna interference.

Not having access to the Wireless CarPlay data spec, I propose a few alternative reasons for this issue:

1) If the GPS data comes to the phone as a raw stream of decoded GPS signals, then it's still up to the phone to do the triangulation math. Since that data is being retransmitted with a delay, the data path would need to include additional latency information. If that latency was incorrectly calculated or became corrupted in memory, then I think we'd see something similar to this issue.

2) If the GPS data comes to the phone as pre-decoded position information, it's possible that that data stream gets corrupted and the phone has no GPS data to go off of. It would then rely on its other systems (cell tower, wifi, accelerometer integration) to get some idea of where it was.

3) If the GPS data comes to the phone as an initial position and then a stream of deltas, then some corrupt data could make the initial position consistently wrong, but the deltas would mean the position would remain wrong by the same offset for the duration of the trip.

Or it could be signal interference.

 

[Chris Brynner]

Remember that GPS is driven by triangulation of satellite signal reception. Depending on the location of the phone in the car, your reception may be limited enough to render the location calculation inaccurate. Some cars (like my 330) have signal boosters for this. I don't think we have any clarity on whether or not the i4 does this, although I believe wireless CarPlay is supposed to include that capability.

The phone triangulation is definitely not the issue. When I opened maps before turning on the car, the position was correct. As soon as I turned on the car and CarPlay connected, the CarPlay map displayed on the car screen was offset.

This wasn’t an issue prior to today.

I tried rebooting my phone, but they did not solve the problem.Disconnecting CarPlay from inside the car also did not. I was able to disconnect CarPlay from the “devices” menu in the car and reconnect. That seemed to resolve the problem.

 

[Chris Brynner]

I had this happen to me today. CarPlay GPS was consistently off, but the BMW map was accurate. The CarPlay map updated its position and direction consistent with my motion. I checked at one point, and CarPlay thought I was exactly one kilometer due north of my actual location. Very strange bug.