How accurate is it?

The average GPS accuracy for GPS trackers is about 50 feet >90% of time. It usually pinpoints the location within 10~200 feet. In rare cases (<5% of time) it can go up to 500 feet.

The main cause of big GPS drifting is the GPS signal "multi-path" issue caused by the reflection of the surrounding objects like buildings, trees, other ground structures, or bad weather (clouds). If you see frequent *big* GPS jumps, it could also be hardware related: the battery level surge, dying battery, or internal GPS chipset issue.

In very rare cases, you may see "huge flying" showing your location is hundreds of miles away or in the middle of ocean. This indicates either a severe reflection of the GPS signal by the buildings/skyscrapers, heavy clouds, or the sudden power surge (check if the battery is dying). And lastly, the GPS hardware could be failing.