Historical map viewer technology that guarantees nonlinear bijective conversion without distortion

Abstract. Historical maps rich in historical information play an important role in fields such as tourism and history education. However, for ordinary people without knowledge of historical studies, it is difficult to understand inaccurate old maps that have not undergone surveying and to comprehend them in comparison with the current city townscape. Therefore, conventionally in GIS, a large number of corresponding points are prepared between an inaccurate historical map and an accurate map, the coordinates of the historical map are converted by forming a triangular mesh and conducting coordinate complement calculation, and the entire historical map image is re-represented by coordinate conversion. However, as shown in Figure 1, with this method there is a serious problem that causes distortion in the aesthetic appearance of the historical map, and remarkable impairment. It can be said that this problem has greatly damaged opportunities to use historical maps for tourism and historical education.

In this paper, we introduce our technology to solve this problem. Our technology has been implemented in the historical map viewer named Maplat, which is available at https://github.com/code4nara/Maplat as MIT-licensed open source.