Open area contains areas with mineral soils or bare rock, which do not qualify for the classes agricultural area, forest, built-up area, transport network or peat bogs. Classes are; 1 Not vegetated; 2 Sparse vegetation; 3 Lichen; 4 Intermediate vegetation; 5 Vigorous vegetation.

The national land resource database (AR) classifies the land cover of mainland Norway according to its suitability for agriculture and natural plant production. National land resource datasets are available at scale 1:5.000 (AR5), 1:50.000 (AR50) and 1:250.000 (AR250).

AR50 is the Norwegian medium resolution land resource dataset which covers the whole of mainland Norway. It is build and maintained for cartographic representations at regional level (1:100.000 to 1:300.000). The dataset is not intended for spatial analysis.

Features in AR50 are continuous areas representated as polygons with attributes assigned according to the AR50 classification criteria. The primary level of classification is land type (arealtype) based on a combination of land cover and land useSecond level attributes are forest site quality class (skogbonitet) and forest cover type (treslag). Areas above the tree line, mountains and other open areas have been classified according to richness of the vegetation. AR50 contain also includes information about arable land when the land cover is bare land, marsh or forest.

In AR50, the general minimum mapping unit is 1.5 hectares for polygons that have identical combinations of attribute values. Smaller mapping units occur between identical land types if they have different forest cover or forest site quality.