What satellites GNSS does it use?
What satellite GNSS does this unit use? I.e the Garmin 810 uses the American GPS while the Garmin 520 uses GPS as well as GLONASS for a more accurate and quicker fix.
I don't know the technical detail, but what I can say is that I have never been let down by it. I use the map functionality a lot up in the lancashire hills and its a great device.