GPS (Global Positioning System) is the modern (space-based) navigation system putting literally your real-time position in (the map that you hold in) your hands.
From 30 October (2011) till 31 July (2015), we've been using the Garmin Dakota 20 device, which accompanied us in great many expeditions in the Bavarian alps.
From 2 August (2015) onward, we're using the Garmin Oregon 600.
The format for GPS devices is GPX.