gps issue

A lot more than the sprecified 2.5m.

Where is 2.5m mentioned?

https://www.gps.gov/systems/gps/performance/accuracy/#:~:text=For%20example%2C%20GPS%2Denabled%20smartphones,receivers%20and%2For%20augmentation%20systems.

Seems to say:

GPS-enabled smartphones are typically accurate to within a 4.9 m (16 ft.) radius under open sky. However, their accuracy worsens near buildings, bridges, and trees.

So I wouldn't expect to get double that accuracy from the Bangle I'm afraid.