Comparing linguistic maps from different surveys

There are four steps in the process of map-making using a computer: 1) Electronic data production, 2) Sorting and mapping data, 3) Comparing, integrating, superimposing, and linking data, and 4) Publishing linguistic maps. The third stage includes comparing linguistic maps from different surveys. In this paper, map comparison in this stage is focused and its examples are introduced to prove that the procedure is necessary to investigate detailed courses of linguistic change. First, linguistic maps of different surveys including the same area are compared to obtain interpretations from different perspectives. Second, linguistic maps targeted for different generation in the same area are compared to illustrate chronological changes shown as geographical distributions.