In this paper, we propose a new method for choosing the most suitable time-series classification method that can be applied to online gamma dose rate incidents. We referred to the historical incidents measured in the German Radiation Early Warning Network and clustered them into several classes before testing existing classification methods. This raises the research problem of the online classification of time-series data with varying scales and lengths. Referring to the state-of-the-art methods, we found that no specific classification method can fit our data all the time. This motivated us to introduce our own approach.