KAST is based on the Canadian model ATES (Avalanche Terrain Exposure Scale), but have been adjusted to better fit the Norwegian conditions. KAST defines the terrain within four classes: 0 - Non avalanche terrain, 1 - Simple, 2 - Challenging and 3 - Complex. For description of the classes go here.
The main difference between ATES and KAST is the introduction to terrain class 0 - Non avalanche terrain. The Norwegian model also focuses more on cornices instead of glaciers. In Norway many severe accidents happens in relation to cornices. Cornices are marked with warning signs in the KAST map for the classified trips.
The KAST map series contains manually classified trips, now available in the regions Romsdalen, Lofoten and Troms. These trips have been classified by local avalanche experts and guides, and are given a class based on the highest terrain class the route is exposed to. To see the Norwegian technical model used to classify the trips click here.
The map series also contains a layer called AutoKAST that covers all of Norway and parts of Svalbard. This layer is generated with using an automatic algoritm. The layer contains the terrain classes challenging and complex in an overview scale. When you zoom further in it will be replaced with a map showing slope angle in combination with modelled short and middle range runouts.