Progress in Signals and Telecommunication Engineering Nina Rešcic, Mitja Luštrek 8 1 2019 http://www.dline.info/pste/fulltext/v8n1/pstev8n1_2.pdf researched. Most commonly classification considers all activities to be ‘equal’ (we will use term at classification). However, intuition suggests better results could be achieved using a hierarchical approach for classification. In this paper we compare three different approaches to classify activities: (i) Flat classification - classes are equal and we build one model to classify all of them; (ii) Multi-model hierarchical classification - classes are arranged in trees, we build different models to classify activities on different levels. We apply two different approaches; (iii) Hierarchical classification using CLUS software1.