Dual XGPS 160 accuracy issues

Discussion related to external and internal GPS / GLONASS / Galileo / BeiDou sensors
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rbpeirce
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Re: Dual XGPS 160 accuracy issues

Post by rbpeirce » Thu Jul 04, 2019 7:48 pm

Interesting. I was going to buy a 160 for exactly that reason, The Track Attack map traces are bizarre and the Track Attack people felt that was because of the 1Hz signal in the iPhone. Apparently not. It is uncorrectable drift, which is probably much worse over a month than an hour.

Apparently GPS readings are nowhere near as accurate as I thought they were. Maybe I should wait to upgrade my hardware or not do it at all. The ONLY reason I felt the need to do it was for Track Attack and Tripper's plot isn't really the much different from what I got using the iPhone for GPS.
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Harry
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Re: Dual XGPS 160 accuracy issues

Post by Harry » Fri Jul 05, 2019 7:27 am

The biggest problem with smartphone‘s internal GPS is accuracy, not update rate. As external receivers have an optimized antenna design, they deliver far better her. The higher update rate is a nice addition for smoother lines too.

As outlined above, the drift is one component reducing accuracy, but as it has almost no influence on lap timing. The problem component is the noise, it is higher for a small. Umber of satellites locked and it is higher for internal GPS due to the compromises smartphone manufacturers needs to make.

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aMacUzr
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Re: Dual XGPS 160 accuracy issues

Post by aMacUzr » Fri Jul 05, 2019 7:04 pm

This "plotted position on the track" accuracy was what I was referring to in my post at
viewtopic.php?f=19&t=5452&p=26650#p26647

For me, the "track plot" in Circuit Tools was more accurate from lap-to-lap throughout the day when using the VBOX as opposed to using the XGPS-160 (actual position judged via integrated front-facing dashcam video). To be fair, however, the number of samples I have are not statistically significant/conclusive.

Harry: I, for one, really appreciate your detailed explanations (of course, I am so much a geek that I think the term is a compliment). #;-) Your support is superb (and, as a software guy, I know how difficult and valuable that is).
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rbpeirce
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Re: Dual XGPS 160 accuracy issues

Post by rbpeirce » Fri Jul 05, 2019 8:30 pm

Tripper. I see the difference in the Track Attack track plot but what about the data traces? I get a lot of variation from the iPhone, and I was considering the add-on GPS to improve that as well as the plot. The traces sometimes overlay exactly and sometimes are off by quite a bit. I'm not talking amplitude, which is what I am trying to examine in many cases, but the tendency for one trace to lead or lag another. Of course, there is some of this in real life, maybe 5-10' or so, but I see one case in the speed trace where a hairpin turn is 200' different and I know that never happened. I also see another case in an acceleration trace where one trace is consistently about 10' sooner than the other. These sort of things greatly reduce the use of the app. I can live with track plot problems but I was hoping a better GPS unit might cure the trace problems.
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