GPS/Map Overlay do not correspond accurately...

[Boozshey]

I am using iPhone 7 DUAL 160 GPS, I noticed that in hard turns the GPS tends to wander off the track and is adding distance to my laps. GPS shows 2.5m accuracy.

However reviewing a friends maps on his Android device and no external GPS his laps all show properly and on course. His GPS shows 4.6m accuracy.

Is this a normal occurrence? Anyway to fix this?

[Weston@HPTuners]

This would suggest a GPS reception / signal issue... I wouldn't put too much thought into comparing the reported accuracy numbers between two different devices, as they are somewhat relative to the GPS being used. We use them as a rough indicator of signal conditions. In my experience, the XGPS doesn't always update its reported accuracy data when there's less than optimal signal, so I would approach problem this by trying to improve the GPS reception conditions.

When inside of a car, under the front windshield or maybe the rear window tends to work best, as that gives the GPS the largest view of the sky with the least obstruction. It's important to avoid metal near it as much as practical, as that can block or reflect the signal. The worst places tend to be in the center of the car (ie under a metal roof), near a roll bar/cage, or anywhere too close to the driver (as you move, it can slightly change the reception conditions).

I have seen some people go to the extreme and mount their GPS on the roof. While I can't generally advise that due to the risk of it coming loose and being lost on track, that would likely be the best available reception location.