Resumen
Schematic maps have widely been used for representing transport networks. In the schematization process, preserving the relative position of nodes and the relative length of segments are considered highly important for constructing spatial cognition. Some researchers have regarded these as general principles of automated schematization. However, in-depth investigations into the conversion of these general principles into specific schematic network map designs are still lacking. This study aimed to empirically investigate how the two relative relations are preserved in existing manually produced schematic maps to better understand and interpret designer thinking. Official underground network maps of 32 cities were used in this study. The results revealed that (1) relative relations were largely preserved with a preservation ratio of approximately 80%, and the global preservation ratios of two relative relations were significantly higher than those of local preservation; (2) the preservation of relative position took priority over the preservation of relative length for the schematic maps with significant enlargement of dense regions; and (3) a reference object may be used for preserving relative relations, for example, the center region or major axis. The findings of this study will assist in developing and/or optimizing design rules for automated schematization while preserving relative relations.