It is not clear what you hope to do Stefan.
What is a Roverstäbe (rover stick);
Is a Roverstab a trak marker, or a listing of location points? something like discussed here National Park Tutorial (Markers) updated
When you add Markers to a Map, you automatically create a Feature Collection that contains the Marker coordinate. The Feature Collection is a geojson.
What have you tried? Sharing what you tried should help us understand what you want to do and why.