Thanks to hints given by TrailRunner users, I added the new Statens Kartverk Digital Map Data Source for Norway — provided by the Norwegian Mapping Authority — to the list of OpenStreetmap sources.

As you can see in the depicted screenshots, the quality is phenomenal.
The Map data goes from a National Map scale down to a very detailed map with properties, buildings and roads.

To view the map data, switch to the openStreetMap source and then zoom in somewhere in Norway, TrailRunner will automatically select the new source and display the background map.

> Norwegian Mapping Authority

Tags: Maps, services, Topographic Maps, openstreetmap